research article cyclic voltammetric study of high speed...

Research ArticleCyclic Voltammetric Study of High Speed SilverElectrodeposition and Dissolution in Low Cyanide Solutions

Bo Zheng12 Lai Peng Wong2 Linda Y L Wu3 and Zhong Chen1

1School of Materials Science and Engineering Nanyang Technological University 50 Nanyang Avenue Singapore 6397982MacDermid Enthone Enthone Chemistry A Division of Alent Singapore Pte Ltd 26 Tuas West Road Singapore 6383823Singapore Institute of Manufacturing Technology 2 Fusionopolis Way No 08-04 Innovis Singapore 138634

Correspondence should be addressed to Bo Zheng bzheng002ntuedusg and Zhong Chen aszchenntuedusg

Received 7 March 2016 Revised 12 May 2016 Accepted 12 May 2016

Academic Editor Sheng S Zhang

Copyright copy 2016 Bo Zheng et alThis is an open access article distributed under theCreativeCommonsAttribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The electrochemical processes in solutions with amuch lower amount of free cyanide (lt10 gL KCN) than the conventional alkalinesilver electrolytes were first explored by using cyclic voltammetry The electrochemical behavior and the effect of KAg(CN)

2

KCN and KNO3electrolytes and solution pH on the electrodeposition and dissolution processes were investigated Moreover

suitable working conditions for high speed low cyanide silver electrodeposition were also proposed Both silver and cyanide ionsconcentration had significant effects on the electrode polarization anddeposition rateTheonset potential of silver electrodepositioncould be shifted to more positive values by using solutions containing higher silver and lower KCN concentration Higher silverconcentration also led to higher deposition rate Besidesmaintaining high conductivity of the solution KNO

3might help reduce the

operating current density required for silver electrodeposition at high silver concentration albeit at the expense of slowing downthe electrodeposition rate The silver dissolution consists of a limiting step and the reaction rate depends on the amount of freecyanide ions The surface and material characteristics of Ag films deposited by low cyanide solution are also compared with thosedeposited by conventional high cyanide solution

1 Introduction

Silver coatings electrodeposited using cyanide-based solu-tions have existed for more than one century Cyanide hasplayed an important role in the silver electrodeposition proc-esses However due to stricter rules and regulations as wellas high cost of wastewater treatment less toxic chemicalshave becomemore favorable in most metal plating processesOver the years compounds such as ammonia [1 2] uracil [3]HEDTA [4] 2-hydroxypyridine [5 6] hydantoin [7] and 55-dimethylhydantoin [8 9] have been suggested as alternativesto replace cyanides in silver plating baths In spite of the ben-efits for using low toxicity cyanide-free silver plating bathsmost of these electrolytes have limited practical applicationsin commercial manufacturing process for reasons such asrelatively higher cost low bath stability high sensitivity totemperature and metallic contamination low deposit qualityand brightness and poor adhesion on substrates [3 10ndash13]

Hence the conventional alkaline electrolyte that is silvercyanide complex [KAg(CN)

2] with excess free cyanide (ie

NaCN or KCN salt in excess of that required to form silvercyanide complexes) remains one of themost commonly usedsystems in the electroplating industries to date Besides beinga conducting salt cyanide is also an excellent complexingagent which complexes not only Ag ions but also othermetallic impurities (especially copper and nickel ions) thatare inevitably present in the plating solutions due to thedisplacement reaction between the substrate and solutionions Impurities build up over time as Cu or Ni dissolves intothe plating solution while Ag precipitates out of the solutionThe free cyanide in the solutions will complex with thesemetallic impurities thereby ensuring high bath stability andlonger bath life In this way consistent high quality of Agdeposit can be obtained

Furthermore with the aid of suitable additives suchas brighteners and levelers cyanide-based silver solutions

Hindawi Publishing CorporationInternational Journal of ElectrochemistryVolume 2016 Article ID 4318178 11 pageshttpdxdoiorg10115520164318178

2 International Journal of Electrochemistry

also improve the roughness and inhomogeneity of coatingsbecause of their good throwing power thus producing con-sistently high quality of white or bright deposits [14 15]Solutions with high throwing power are favorable in theplating process because they ensure uniform deposit onplated parts especially on those with complex geometries aswell as uneven current distribution

On the other hand cyanide-free silver plating solutionsoften make use of the weak chelating agent which only formsweak complexeswith themetallic impurities As a result poorsilver deposits are always formed in aging cyanide-free silverplating solutions as these metallic impurities are codepositedwith silver The weak silver complex formed in cyanide-freesilver plating solutions also increased the activity of free Agions which facilitates the displacement reactions betweensubstrate and silver ions releasing more metallic impuritiesinto the plating solutions

As a consequence manufacturers still tend to stay withcyanide-based solutions due to their high bath stability easeof operation and consistently high quality of silver coat-ings Implementing cyanide-free plating solutions in manu-facturing industries remains a great challenge [9]

Electrodeposited silver has been playing important rolesin decorative applications and electronics industries for dec-ades In response to the high demands in advanced electron-ics products good quality silver plating at high speed hasbecome a critical step in the manufacturing process More-over new applications in electronics and semiconductorindustries have also encouraged the development of newsilver chemistries for high speed selective plating such asmirror bright silver spot plating on leadframes

Similar to conventional alkaline silver electrolytes highspeed silver plating solutions usually have high potassiumcyanide content (45ndash100 gL) and are not suitable for selectiveor spot plating [16] In high speed silver spot plating onleadframes the leadframes are plated with silver to give abondable area on the lead finger to allow a second bond toform subsequently This area must be slightly larger than thesize of the second bond Insoluble anodes such as platinisedtitanium mesh or platinum wire are commonly used as onlythe tip of the lead finger is plated for bonding [17] Oxidationand polymerization of cyanide [18] at these insoluble anodeshave caused rapid degradation of the high cyanide silverplating solutions

Hence it would be desirable if the negative effect ofcyanide is minimized while at the same time the high qualityof silver coatings could be maintained consistently Besidesthat because of the low cyanide content the accumulation ofcarbonates could be slowed down As a consequence the lowcyanide silver bath life could also be extended

In this work the silver electrochemical processes insolutions consisting of a much lower amount of free cyanide(lt10 gL KCN) than the conventional alkaline silver elec-trolytes were first explored by using cyclic voltammetrictechnique The electrochemical behaviors and effects ofthe basic electrolytes (silver salt potassium cyanide andconducting salt) and solution pH on the electrodepositionand dissolution processes were also investigated In addition

the optimum working conditions for high speed silver elec-trodeposition in low cyanide system were also proposed

In order to ensure the feasibility of replacing high cyanidewith low cyanide system in practical applications the charac-teristics such as morphologies purity brightness conductiv-ity and hardness of Ag films electrodeposited by low cyanidesystem will also be compared with those electrodeposited byconventional high cyanide silver solution

2 Materials and Methods

21 Chemicals and Plating Conditions Chemicals used werepotassium silver (I) cyanide (KAg(CN)

2) potassium nitrate

(KNO3) potassium cyanide (KCN) nitric acid (HNO

3) and

potassium hydroxide (KOH) All solutions were preparedwith deionized water The pH of the solution was adjusted byusing either 1 HNO

3or 1 KOH solutions

Brass hull cell panel was used as a substrate for silverelectrodeposition All the pretreatment Ni and Ag electrode-position chemicals used are proprietary products providedby MacDermid Enthone Before deposition the brass wascleaned in the Enprep 110 EC Enprep 220 EC and Actane345 After that the brass was electrodeposited with a layer ofnickel (2-3 120583m) by usingHeliofabNi-370 Next a thin layer ofAg was electrodeposited on the Nibrass panel by using twotypes of silver solutions that is low cyanide silver solutionand conventional high cyanide silver solution The low cya-nide silver solution was made up of 120 gL KAg(CN)

2

6 gL KCN 120 gL KNO3 5mLL XRD Ag-7000 B1 and

16mLL XRD Ag-7000 B2 while the high cyanide silversolution consisted of 100 gL KAg(CN)

2 150 gL KCN 6 gL

KOH 20 gL K2CO3 5mLL Heliofab Ag-900 C and T and

3mLL Heliofab Ag-900 HThe electrodeposition conditionsfollowed the optimum parameters as recommended in theXRD Ag-7000 and Heliofab Ag-900 technical datasheetsThe pH values of the freshly prepared silver solutions wereadjusted to about 10ndash12 for both low and conventional highcyanide solutions

The current densities used for the electrodeposition are06 Acm2 for low cyanide system and 003Acm2 for con-ventional high cyanide system The deposition time of thetwo systems was adjusted so that the Ag films had a similarthickness at 20ndash25 120583m

22 Cyclic Voltammetric Analysis The electrochemical stud-ies of silver electrodeposition anddissolutionwere performedin a conventional three-electrode cell using computerizedpotentiostat (797VA Computrace Metrohm) at room tem-perature Polished platinum rotating disk (Metrohm 119860 =00314 cm2) was used as the working electrode During theexperiments AgAgCl (3M KCl) reference electrode wasmounted in an electrolyte vessel filled with 1M KNO

3solu-

tion and used as a double junction reference electrode Allthe potential measured in the voltammetric study referred tothis reference electrode A platinum rod which representedthe insoluble anode in industrial practice was employed asthe counter electrode All the silver electrodeposition anddissolution processes were studied at angular speed (120596) of1200 rpm The cyclic voltammetry scan rate was 50mVsminus1

International Journal of Electrochemistry 3

Before each measurement the electrode was cleaned indeionized water followed by 50 HNO

3solution and 10

KOH solution and rinsed with deionized water After thatthe electrode was sonicated in deionized water for 5minbefore use

23 Ag Films Characterization The surface morphology ofthe Ag films was observed under scanning electron micro-scope (SEM JSM-6360A JEOL) while their surface rough-ness wasmeasured using atomic forcemicroscope (AFMDI-3100 Digital Instruments) Furthermore X-ray diffraction(XRD) analysis was also performed for characterizing thecrystal orientation of the surfaces of electrodeposited Agfilms Thin Film XRD (XRD-6000 Shimadzu) with Cu K

120572

radiation (40 kV 30mA)was usedThe sampleswere scannedcontinuously at 2∘ 2120579minminus1 The compositional profile of thesilver films was investigated by X-ray photoelectron spec-troscopy (Thermo Scientific ESCALAB 250Xi) The sampleswere scanned by Al K

120572(14866 eV) radiation

The brightness or reflectance of the Ag films was deter-mined by using a spectroscopic reflectometer (RadiTech) ata light incidence angle of 0∘ Silicon-based wafer was usedas the reference and the intensity change of light reflectedfrom the surface of Ag samples was measured as a functionof wavelength (120582 = 450 nm) at normal incidence Reflectancereadings were taken at 120582 = 450 nm (blue light) because thiswavelength is more critical in the LED application A four-point probe (CMT-SR2000N AIT) was used to measure theresistivity of the Ag samples The hardness of the Ag layerwas measured by Micro Hardness Tester (Shimadzu HMV-2) with a 50 g load

3 Results and Discussion

31 Cyclic Voltammetry of AgAg+ at Rotating Disk PlatinumElectrode The voltammetric studies of KAg(CN)

2 KNO

3

and KCN electrolytes and solutions pH were performed overthe platinum rotating disk electrode in order to analyzethe different redox processes and to determine the suitableworking potential range for silver electrodeposition Rotatingdisk electrode was used in the experiments because it gaveagitation to the solutionwhich could reduce the thickness andprevent the impoverishment of diffusion layer lying betweenthe bulk solution and the working electrode surface therebyensuring uniform deposition

Figure 1(a) shows the redox reactions of 120 gLKAg(CN)

2in the absence or presence of KNO

3and KCN

During the 1st scan cycle of 120 gL KAg(CN)2 it is observed

that a drastic increase in the cathodic current appears atsimminus041 V (Figure 1(a) peakC1) and an anodic reaction occursat simminus2mV (Figure 1(a) peak A1) corresponding to the silverelectrodeposition and silver film dissolution respectivelyAn additional cathodic peak C2 became pronounced aroundminus50mV during the 2nd scan cycle (Figure 1(b)) This maybe due to the incomplete silver dissolution during the firstanodic scan giving rise to the presence of oxidized and non-dissolved silver film on the platinum surface from the begin-ning of the next scan [19]

In contrast to the onset potential of silver electrodeposi-tion at the 1st scan cycle the reduction of silver ions starts ata more positive potential from the 2nd scan cycle onwardswhich is at simminus280mV As platinumworking electrode (whichis different from the deposited metal) is employed theinitiation of nucleation normally consumes more energy toproduce the first nucleus [20] Besides that the presence ofnondissolved silver film on the electrode may also facilitatethe nucleation and growth processes during the 2nd scancycle

The addition of supporting electrolyte KNO3to 120 gL

KAg(CN)2solution has significantly lowered the cathodic

current density of silver reduction as a steady-state limitingcurrent is achieved when compared to that that occurs inthe KAg(CN)

2solution without supporting electrolyte This

is because the migration effect of silver ions is minimized inthe presence of supporting electrolyte

It is clear that in the presence of KCN the onset potentialof silver electrodeposition is shifted to more negative values(Figure 1(a) peak C3) while the silver dissolution wave(peak A2) becomes broader and the anodic current densityreaches a plateau before it drops abruptly When the vertexpotential of cathodic scan is raised to more negative valuesthe amount of silver deposited is enhanced as depicted bythe increase in the dissolution wave areas in Figure 1(c) Thecyclic voltammogram also shows a characteristic hysteresiswhich appears after potential sweep reversal This is thecharacteristic of metal nucleation or growth on workingelectrode [21] In addition steady-state limiting current ofsilver electrodeposition is achieved around minus083V and theproton reduction or hydrogen evolution is noticed to occurbeyond simminus086V Any deposition carried out beyond thesenegative potentials might produce silver filmwith pitting andadhesion defects [13 22] As a result the silver electrodeposi-tion process will only be examined below minus08V in this study

Assuming that only Ag(CN)2

minus complexes exist in thesolutions and all silver atoms come from this complex thecharge transfer of silver electrodeposition in Figure 1(a)peaks C1 and C3 can be described by (1) The difference inthe free cyanide concentration in the solution has inducedthe change in the onset potential of electrodeposition Onthe contrary the dissolution of Ag (peak A2) can also berepresented by the reverse reaction of

Ag(CN)2

minus+ eminus 999447999472 Ag + 2CNminus (1)

However several chemical steps such as the dissociationof cyanide ions reduction of silver ions and removal ofcyanide ions from the electrodeelectrolyte interface maytake place simultaneously as well Another situation thatinvolves the partial or complete dissociation of Ag(CN)

2

minus

anion is shown in (2)ndash(5) [23] The cathodic peak C2 shownin Figure 1(b) corresponds to (5) where the reduction ofnondissolved Ag film occurs Hence

Ag(CN)2

minus999447999472 AgCN + CNminus (2)

AgCN 999447999472 Ag+ + CNminus (3)

Ag+ + eminus 999447999472 Ag (4)

AgCN + eminus 999447999472 Ag + CNminus (5)


C1

C2

A1A2

C3

120 gL KAg(CN)2 in 120 gL KNO3 solution120 gL KAg(CN)2 6gL KCN in 120 gL KNO3 solution

minus06 minus04 minus02 0 02 04 06minus08E (V)

minus70

minus50

minus30

minus10

10

30

i(m

A cm

minus2 )

120 gL KAg(CN)2 solution 1st cycle120 gL KAg(CN)2 solution 2nd cycle

(a)

C1C2

A1

minus05 minus03 minus01 01 03 05minus07E (V)

minus70

minus50

minus30

minus10

10

30

i(m

A cm

minus2 )


(b)

minus08 minus06 minus04 minus02 0 02 04 06minus1E (V)

minus70

minus50

minus30

minus10

10

30

50

minus09Vminus10V

minus07Vminus08V

i(m

A cm

minus2 )

(c)

Figure 1 Cyclic voltammograms of (a) silver electrodeposition and silver dissolution in the absence and presence of KNO3and KCN (b)

120 gL KAg(CN)2only (c) the influence of cathodic vertex potential in 120 gL KAg(CN)

2 6 gL KCN and 120 gL KNO

3solutions Arrows

show the potential sweep direction Initial potential = +06V Sweep rate 50mVsminus1 C1 C2 and C3 denote the cathodic peaks while A1 andA2 correspond to the anodic peaks

In fact the silver electrodeposition process in cyanidesystem involves more complicated mechanisms because ofthe formation of more than one silver complex that isAgCN Ag(CN)

2

minus Ag(CN)3

2minus and Ag(CN)4

3minus in whichequilibrium concentration and the predominant species thattake part in the charge transfer process rely on the cyanideconcentration in the solutions [24] When the free cyanide isinsufficient the dissolution of Ag (Figure 1(b) peak A1) mayproceed in the reverse direction of (5)

32 The Effect of KAg(CN)2 Concentration on the Electrode-position of Silver Figure 2(a) shows the effect of KAg(CN)

2

concentration on the silver electrodeposition as well as silver

dissolution When the amount of KAg(CN)2is increased

from 60 to 200 gL in the solutions containing 6 gL KCN theonset potentials of silver electrodeposition are shifted towardsmore positive values (Figure 2(b)) In other words as thesource of silver increases the cathodic polarization is low-eredWhen the amount of KCN remains constant increasingKAg(CN)

2concentration will increase the number of silver

cyanide complex ions as well as the silver cations in the solu-tion thus lowering the cyanide coordination number of silvercomplex enabling the deposition to proceed more easily

Moreover higher KAg(CN)2

concentration enableshigher current densities as well as larger amount of silverdeposited resulting in higher electrodeposition rate (Fig-ure 2(c)) This also implies that a large amount of silver salt


minus06 minus05 minus04 minus03 minus02 minus01 0 01minus07E (V)

minus50

minus40

minus30

minus20

minus10

0

10

20

30

60gL80gL

120 gL

140 gL160 gL180 gL200 gL

100gL

i(m

A cm

minus2 )

minus1012345678

i(m

A cm

minus2 )

minus03 minus02 minus01 0 01minus04

E (V)

(a)

70 90 110 130 150 170 190 21050KAg(CN)2 (gLminus1)

minus071

minus070

minus069

minus068

minus067

minus066

minus065

minus064

minus063

minus062

E (V

)(b)

80 100 120 140 160 180 200 22060KAg(CN)2 (gLminus1)

000

100

200

300

400

500

600

700

800

900

Dep

ositi

on ra

te (120583

m m

inminus

1 )

(c)

Figure 2 (a) Cyclic voltammograms of silver electrodeposition and silver dissolution in the solutions consisting of 6 gL KCN 120 gL KNO3

and 60ndash200 gL KAg(CN)2 Inset the current response of second anodic peak increases with increasing KAg(CN)

2concentration during the

anodic scan (b) The effect of KAg(CN)2concentration on the onset potential of silver electrodeposition (c) The influence of KAg(CN)

2

concentration on the electrodeposition rate in the sweeping potential range from +06V to minus07 V

is critical for high speed silver plating Deposition rate isdetermined by

Deposition rate =119876119872Ag

119865120588Ag119860119905times 104(120583mmin) (6)

where 119876 (C) is the charge involved in the silver dissolution119872Ag (= 1078682 gmol) is the molar mass of silver 119865 (=964853365 Cmol) is the Faraday Constant 120588Ag (= 1049 gcm3) is the density of silver 119860 (= 00314 cm2) is the Pt elec-trode area 119905 (min) is the deposition time during the cathodicsweep

It is observed that one main silver dissolution wave andone shoulder peak appear during the anodic scan (Fig-ure 2(a)) At low cyanide (6 gL KCN) and high KAg(CN)

2

(gt120 gL) concentration the dissolutionwaves of silver covera broad potential range and achieve a steady-state limitingcurrent This may be due to the rate limiting steps which areinvolved in the cyanidation of dissolved silver

On the other hand the splitting of the dissolution wavecan be due to the formation of different silver complex inthe solutions Increase in the KAg(CN)

2concentration has

also raised the anodic peak current at simminus31mV (Figure 2(a)inset) This shoulder peak is attributed to the formation ofAgCN as the concentration of free cyanide available in thesolution is insufficient to form soluble silver complex Thisis even more noticeable when the amount of deposited Agincreased with increasing KAg(CN)

2concentration while the

free cyanide concentration remains constant


33 The Effect of KCN Concentration on the Electrodepositionof Silver It has been shown in Figure 1 that in the presence ofKCN both silver electrodeposition and silver film dissolutionreactions are clearly shifted towardsmore negative potentialsDepending on the cyanide concentration in the solution thecoordination number of silver cyanide complexes and thepredominant complex ions will change accordingly following(7)ndash(10) [25] The species that are involved in the chargetransfer process rely not only on the cyanide concentrationbut also on the operating conditions Previous studies [2627] had reported that it was the AgCN that is involved inthe charge transfer when free cyanide [CNminus] was in theconcentration range of less than 01M (26 gL) whereasAg(CN)

2

minus complex took part in the charge transfer stepwhen [CNminus]gt 02M (52 gL) At high cyanide concentration[CNminus] gt 09M (234 gL) Ag(CN)

3

2minus complex was suggestedto be the species that is involved in the charge transfer processOn the other hand the impedance study by Baltrunas [28]had shown that Ag(CN)

2

minus complex is always involved inthe direct charge transfer step regardless of the cyanideconcentration and the composition of the solutions Hence

Ag+ + CNminus 999447999472 AgCN (7)

Ag+ + 2CNminus 999447999472 Ag(CN)2

minus (8)

Ag(CN)2

minus+ CNminus 999447999472 Ag(CN)

3

2minus (9)

Ag(CN)3

2minus+ CNminus 999447999472 Ag(CN)

4

3minus (10)

Generally due to the strong complex-forming effectbetween the cyanide ions and silver ions the cyanide ions willshift the equilibrium potential to more negative values andincrease the activation polarization by reducing the activityas well as the concentration of the free Ag+ ions [14] As aresult in contrast to the effect of increasing the KAg(CN)

2

concentration the higher the KCN concentration the morenegative the potential required to deposit silver coating onplatinum electrode (Figure 3) The difference in the onsetpotential of silver electrodeposition between the solutionscontaining 6 gL KCN and 0 gL KCN was about minus038VUnlike cyanide-free silver electrolytes cyanide-based silverelectrolytes with the addition of suitable brighteners alwaysproduce white and bright silver deposits This is becausethe increase in the cathodic polarization helped promote thegrowth of fine-grained deposits [14]

High level of free cyanide is necessary in order to main-tain consistent and high quality of silver coatings in industrialpractice However in the case of high speed selective platingwhere insoluble anodes are commonly employed the silverplating solution should contain only as much free cyanide asnecessary so that the formation of insoluble AgCN [29] at theanodes which will impede the current flow can be avoided

According to Figure 3 less than about 45 gL KCN in asolution consisting of 120 gL KAg(CN)

2and 120 gL KNO

3

will ensure that the potential required to initiate the silverelectrodeposition will not occur in parallel with the hydrogenevolution reaction Since it is critical that only very low andnecessary amount of KCN should be used in developingthe new silver plating chemistry 4ndash8 gL KCN in the low

minus080minus070minus060minus050minus040minus030minus020

E (V

)

102 3 4 5 6 7 8 910

KCN (gLminus1)

140120100 160 180604020 800KCN (gLminus1)

minus105

minus095

minus085

minus075

minus065

minus055

minus045

minus035

minus025

E (V

)

Figure 3 The effect of KCN concentration on the onset potentialof silver electrodeposition The silver plating solution consists of120 gL KAg(CN)

2 120 gL KNO

3 and 0ndash160 gL KCN Inset the

onset potential of silver electrodeposition in the range of 0ndash10 gLKCN

cyanide region (lt10 gL) is found to be suitable under theexisting given KAg(CN)

2and KNO

3concentrations because

a slight drop or increase in the KCN concentration will notsignificantly affect the polarization of the working electrodeand thereby the plating solutions will be easier to controlduring operation

34The Effect of KNO3 Concentration on the Electrodepositionof Silver As mentioned previously addition of support-ing electrolyte KNO

3to the solution containing 120 gL

KAg(CN)2has lowered the cathodic current density signif-

icantly The same behavior is also observed in the solutionconsisting of 120 gLKAg(CN)

2and 6 gLKCN inFigure 4(a)

The higher the KNO3concentration the lower the cathodic

current density and as a consequence lesser silver is depositedon Pt electrode The decrease in the dissolution peak areaswith increasing KNO

3concentration has also suggested that

KNO3can be used to adjust the rate of electrodeposition

process at constant applied potential as shown in Figure 4(b)The cathodic current density in the absence or at a low

concentration of KNO3is obviously larger than that at higher

concentration because the migration of the Ag+ towards theworking electrode during the cathodic scan has enhancedthe faradaic current At high concentration of KNO

3 K+

migration replaces that of Ag+ and thus the observed faradaiccurrent ismainly contributed by the diffusion current [30] Inthis way KNO

3can improve the conductivity of the solution

and it can also be used to control the deposition rate ifrequired during application

On the other hand unlike KAg(CN)2and KCN KNO

3

does not alter the onset potential of electrodeposition processsignificantly Moreover in contrast with the influence ofKNO3on the current density of silver electrodeposition

increasingKAg(CN)2concentration has the opposite effect in

which the current density increases with increasing silver ionconcentration at constant potential In other words adding


minus07 minus06 minus05 minus04 minus03 minus02 minus01 0 01 02 03minus08E (V)

0gL30gL60gL90gL

120 gL150gL180gL

minus60minus50minus40minus30minus20minus10

010203040

i(m

A cm

minus2 )

(a)

200

300

400

500

600

700

800

900

1000

Dep

ositi

on ra

te (120583

m m

inminus

1 )

30 60 90 120 150 1800KNO3 (gLminus1)

(b)

Figure 4 (a) Cyclic voltammograms of silver electrodeposition and silver film dissolution in the silver plating solution consisting of 120 gLKAg(CN)

2 6 gL KCN and 0ndash180 gL KNO

3 (b)The effect of 0ndash180 gL KNO

3on the deposition rate by sweeping the potential from +06V

to minus07 V

pH 80pH 85pH 90pH 95pH 100

pH 105pH 110pH 115pH 120

minus05 minus03 minus01 01 03minus07E (V)

minus40

minus30

minus20

minus10

0

10

20

30

i(m

A cm

minus2 )

(a)

85 9 95 10 105 11 115 128pH

minus070

minus065

minus060

minus055

minus050

E(V

) ver

sus A

gA

gCl (3

M K

Cl)

(b)

Figure 5 (a) Cyclic voltammograms showing the silver electrodeposition and silver film dissolution in the solutions consisting of 120 gLKAg(CN)


3at pH 8ndash12 (b) The effect of pH of the silver solutions on the onset potential of electrodeposition

of silver ion on Pt electrode surface

more KNO3salt may help to reduce the operating current

density required for silver electrodeposition at high silverconcentration Normally the high current density approach-ing the diffusion limiting current is not recommended inindustrial practice because of the inverse effects due to thedepletion of silver ions in the double layer and the highpossibility of causing hydrogen evolution leading to roughand poor deposit [31]

35 The Effect of Bath pH on the Electrodeposition of SilverSilver cyanide complexes are known to be unstable at verylow pH because of the formation of insoluble AgCNThis hasimposed that the silver cyanide solution must be maintainedin alkaline condition Figures 5(a) and 5(b) show that increas-ing pH of the silver electrodeposition solution from 81 to 10has shifted the onset of electrodeposition potential of silverto more negative direction and then the pH remains constant


in the range of 10ndash12 pH less than 90 has a greater impact onthe onset of silver electrodeposition potential

The silver dissolution starts at around minus065V there isone main dissolution peak followed by a shoulder peak AtpH gt 9 silver dissolution is dominated by the main peakaround minus035V while the shoulder peak is much smallerOn the other hand the shoulder peaks around 10mV areconsiderably large when the solution pH is lower than90 These peaks are positioned at the same potential withthe oxidation peak of KAg(CN)

2solution as depicted in

Figure 1(b) This suggested that at pH lt 9 the presence of[Ag(CN)

2]minus is very pronounced at the platinum electrode

Incomplete dissolution of silver at pH 81 was observedwhen the anodic scan was swept until +06V The unusuallylong dissolution process in solution at pH 81 suggests thatthe deposited silver is coarse and not homogeneous enoughto fully cover the platinum electrode surface as the oxidationpeak of [Ag(CN)

2]minus ion is also observed As a consequence

the optimum pH for the silver electrodeposition solutionshould be kept at gt95 or favorably 10ndash12 as under thiscondition the onset potential of silver electrodepositionremains quite constant and hence easier to control during thedeposition process

36 Effect of KCNon theAnodicDissolution ofDeposited SilverThe rate of anodic dissolution of metals strongly relies onthe solution composition particularly the type of anion andconcentration [32] For silver its dissolution process involvesfree cyanide ions and depends on the cyanide concentrationin the solution The role of free cyanide in the dissolutionof deposited silver can be described by (11) even though thedissolution process also involves the diffusion of free cyanideions towards the silver surface adsorption of cyanide ionsand formation of chemical bond with silver atom as well ascharge transfer [33 34]

The dissolution of deposited silver in cyanide containingsolutions is represented as follows

Ag + 2CNminus(119887)997888rarr Ag (CN)minus

2(119887)+ eminus (11)

When increasing the cathodic vertex potential to morenegative values the silver dissolution waves in the solutioncontaining 6 gL KCN seem to have reached the steady-state limiting current and cover a broad range of potentials(Figure 1(c)) whereas in the solution containing 40 gLKCNthe silver dissolution peaks are sharper and the peak currentshave also increased accordingly (Figure 6)This has indicatedthat the silver dissolution process consists of a limiting stepand the reaction rate depends on the amount of free cyanideions It was reported that the dissolution of silver was limitedby a stage of cyanide ions diffusion towards the electrode sur-face [16 35] As a larger amount of free cyanide is available inhigh KCN containing solutions the dissolution of depositedAg is facilitated by the diffusion of free cyanide ions

Figure 2(a) has also shown that regardless of the amountof silver ions in the 6 gL KCN solutions the dissolutionbehavior is similar to those observed in low free cyanidecontaining solutions The dissolution waves cover a verybroad range of potentials which increases with increasing

minus10Vminus09V

minus11V

minus12Vminus13V

minus10 minus07 minus04 minus01 02 05minus13E (V)

minus200

minus150

minus100

minus50

0

50

100

150

200

i(m

A cm

minus2 )

Figure 6 The current responses of dissolution of silver to differentcathodic vertex potentials in the solution containing high potassiumcyanide electrolyte Electrolyte 40 gL KCN 120 gL KAg(CN)

2 and

120 gL KNO3 Initial potential +06V

KAg(CN)2concentration The anodic current densities of

silver remain at plateau before they drop rapidly This alsoimplies that increasing the KAg(CN)

2concentration does not

help to increase the amount of free cyanide ions

37 Characterization of the Plated Ag Films The surface mor-phologies of Ag films electrodeposited by conventional highcyanide and the low cyanide silver solutions are shown inFigures 7(a)-7(b) It can be seen that there is no significantdifference in the surface morphologies of the two Ag filmsThe surfaces of both Ag films appear to be quite smoothMoreover the AFM analysis has confirmed that the surfaceroughness (119877a) of both Ag films is comparable 119877a of Ag filmselectrodeposited by high cyanide and low cyanide systems are88 nm and 98 nm respectively (Figures 7(c)-7(d))

The XRD patterns in Figure 8 have also clearly shownthat both Ag films are polycrystalline and exhibit (111) (200)(220) and (311) peaks These four peaks are consistent withthe published XRD diffraction result of Ag with puritygt99999 (JCPDS file number 04-0783) [36] In additionthe crystallites of Ag film electrodeposited using low cyanidesilver solution have the same preferred orientation in (111)plane as the film electrodeposited by using conventional highcyanide system

The XPS depth profiles of the Ag films prepared fromlow cyanide and high cyanide solutions are also comparedin Figure 9 Low cyanide Ag films have 100 Ag after thedepth of about 4 nm while high cyanide Ag films have 100Ag after 6 nm No other impurities are observed thereaftershowing high purity of both Ag films Elements such assulphur oxygen and carbon are also detected from the Agsurfaces These contaminants are from the environment andare often adsorbed on sample surfaces


00

100

200

300

400

500

600

700

800876

(nm

)

Ra = 88nm

(c)

00

100

200

300

400

500

600

700

800

900

10001055

(nm

)

Ra = 98nm

(d)(d)

Figure 7 Scanning electron micrographs of Ag films electrodeposited by (a) high cyanide and (b) low cyanide silver solutions the 3D AFMimages and surface roughness (119877a) of Ag films electrodeposited by (c) high cyanide and (d) low cyanide silver solutions

Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(a)

Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(b)

Figure 8 XRD patterns of Ag films electrodeposited by (a) high cyanide and (b) low cyanide silver solutions The 119910-axes of all panels arepresented in the same scale

Under optimum conditions the average reflectance (119877)of Ag films electrodeposited by both low cyanide and con-ventional high cyanide systems at 120582 = 450 nm is determinedto be around 90ndash95 This shows that the brightness of theAg films electrodeposited by low cyanide is comparable withthe brightness of those electrodeposited by conventional highcyanide silver solution

Besides that both types of Ag films have comparablehardness in the range of about 100ndash120 Hv

005 On the other

hand the resistivity of Ag films electrodeposited by lowcyanide and high cyanide solutions is found to be around0497 plusmn 002 120583Ωsdotcm and 0503 plusmn 001 120583Ωsdotcm respectively

4 Conclusion

The study shows the electrochemical behaviors of KAg(CN)2

KCN and KNO3electrolytes and solutions pH on the

silver electrodeposition and dissolution Higher silver ionconcentration shifts the onset potential of silver electrodepo-sition to more positive direction by lowering the electrodepolarization while KCN has the opposite effect in chang-ing the cathodic polarization The onset potential of silverelectrodeposition is shifted to more negative values withincreasing KCN concentration High plating speed or depo-sition rate can be attained in solutions containing high


Ag3dS2pO1sC1s

Ag3dS2pO1sC1s

Low CN High CN

10 20 30 40 50 60 70 80 900Depth (nm)

00

200

400

600

800

1000

Atom

ic p

erce

nt (

)

Figure 9 Compositional profile ofAg films prepared by low cyanideand high cyanide systems as a function of etched depth

silver concentration Besides having little impact on theonset potential of silver electrodeposition KNO

3lowers the

limiting current density as well as the electrodepositionrate This implies that KNO

3may help reduce the operat-

ing current density required for silver electrodeposition inhigh silver concentration solutions albeit at the expense ofslowing down the electrodeposition rate The silver platingsolutions should bemaintained at pH range 10ndash12 as the onsetpotential of silver electrodeposition remains quite constantand hence easier to control during the operating processThe silver dissolution process consists of a limiting step andthe reaction rate depended on the amount of free cyanideionsThe surface characteristics such asmorphologies puritybrightness and conductivity as well as hardness of Ag filmselectrodeposited by low cyanide system are comparable withthose electrodeposited by conventional high cyanide systemTheXRDanalysis andXPS depth profile have also shown veryhigh purity of both types of Ag films

Competing Interests

The authors declare that there are no competing interestsregarding the publication of this paper

Acknowledgments

The authors wish to thank MacDermid Enthone EnthoneChemistry for their equipment and financial support Theywould also like to thank Mr Swapan K Biswas and Mr GohMin Hao for their technical advice and support

References

[1] B J Polk M Bernard J J Kasianowicz M Misakian and MGaitan ldquoMicroelectroplating silver on sharp edges toward the

fabrication of solid-state nanoporesrdquo Journal of the Electrochem-ical Society vol 151 no 9 pp C559ndashC566 2004

[2] M Miranda-Hernandez and I Gonzalez ldquoEffect of potentialon the early stages of nucleation and growth during silver elec-trocrystallization in ammonium medium on vitreous carbonrdquoJournal of the Electrochemical Society vol 151 no 3 pp C220ndashC228 2004

[3] B-G Xie J-J Sun Z-B Lin and G-N Chen ldquoElectrodepo-sition of mirror-bright silver in cyanide-free bath containinguracil as complexing agent without a separate strike platingprocessrdquo Journal of the Electrochemical Society vol 156 no 3pp D79ndashD83 2009

[4] G M de Oliveira M R Silva and I A Carlos ldquoVoltammetricand chronoamperometric studies of silver electrodepositionfrom a bath containing HEDTArdquo Journal of Materials Sciencevol 42 no 24 pp 10164ndash10172 2007

[5] Z-B Lin B-G Xie J-S Chen J-J Sun and G-N ChenldquoNucleation mechanism of silver during electrodeposition on aglassy carbon electrode froma cyanide-free bathwith 2-hydrox-ypyridine as a complexing agentrdquo Journal of ElectroanalyticalChemistry vol 633 no 1 pp 207ndash211 2009

[6] Z-B Lin J-H Tian B-G Xie et al ldquoElectrochemical andin Situ SERS studies on the adsorption of 2-hydroxypyridineand polyethyleneimine during silver electroplatingrdquo Journal ofPhysical Chemistry C vol 113 no 21 pp 9224ndash9229 2009

[7] R Morrissey ldquoNon-cyanide silver plating bath compositionrdquoUS Patent no 20070151863 A1 2007

[8] M Clauss andW Zhang-Berlinger ldquoCyanide-free silver electro-plating solutionsrdquo United States Patent No 8608932 B2 2012

[9] A Liu X Ren B Wang et al ldquoComplexing agent study viacomputational chemistry for environmentally friendly silverelectrodeposition and the application of a silver depositrdquo RSCAdvances vol 4 no 77 pp 40930ndash40940 2014

[10] A Liu X Ren M An et al ldquoA combined theoretical and exper-imental study for silver electroplatingrdquo Scientific Reports vol 4article 3837 2015

[11] S Jayakrishnan S R Natarajan and K Vasu ldquoAlkaline non-cyanide bath for electrodeposition of silverrdquo Metal Finishingvol 94 no 5 pp 12ndash15 1996

[12] S Sriveeraraghavan RMKrishnan and S RNatarajan ldquoSilverelectrodeposition from thiosulfate solutionsrdquo Metal Finishingvol 87 pp 115ndash117 1989

[13] N Okamoto F Wang and T Watanabe ldquoAdhesion of elec-trodeposited copper nickel and silver films on copper nickeland silver substratesrdquoMaterials Transactions vol 45 no 12 pp3330ndash3333 2004

[14] V S Bagotsky ldquoReactions involvingmetalsrdquo in Fundamentals ofElectrochemistry pp 297ndash317 John Wiley amp Sons 2005

[15] M Schwartz ldquoDeposition from aqueous solutions an over-viewrdquo in Handbook of Deposition Technologies for Films andCoatings R F Bunshah Ed p 506 Noyes Publications ParkRidge NJ USA 1982

[16] M Schlesinger and M Paunovic Modern Electroplating JohnWiley amp Sons 2011

[17] S K Prasad Advanced Wirebond Interconnection TechnologySpringer Science amp Business Media Berlin Germany 2004

[18] H Tamura T Arikado H Yoneyama and Y Matsuda ldquoAnodicoxidation of potassium cyanide on platinum electroderdquo Elec-trochimica Acta vol 19 no 6 pp 273ndash277 1974

[19] I Krastev A Zielonka S Nakabayashi and K Inokuma ldquoAcyclic voltammetric study of ferrocyanide-thiocyanate silver


electrodeposition electrolyterdquo Journal of Applied Electrochem-istry vol 31 no 9 pp 1041ndash1047 2001

[20] V F C Lins M M R Castro C R Araujo and D B OliveiraldquoEffect of nickel and magnesium on zinc electrowinning usingsulfate solutionsrdquoBrazilian Journal of Chemical Engineering vol28 no 3 pp 475ndash482 2011

[21] S Fletcher ldquoSome new formulae applicable to electrochemicalnucleationgrowthcollisionrdquo Electrochimica Acta vol 28 no 7pp 917ndash923 1983

[22] Z Zainal S Nagalingam and T M Hua ldquoProperties of tinsulphide thin films electrodeposited in the presence of tri-ethanolaminerdquo Journal of Materials Science Materials in Elec-tronics vol 16 no 5 pp 281ndash285 2005

[23] A M Azzam and I A W Shimi ldquoStudies of the propertiesof silver cyanide complexesrdquo Zeitschrift fur Anorganische undAllgemeine Chemie vol 321 no 5-6 pp 284ndash292 1963

[24] OAAshiru and J PG Farr ldquoApplication of frequency responseanalysis to the determination of cathodic discharge mechanismduring silver electroplatingrdquo Journal of the ElectrochemicalSociety vol 142 no 11 pp 3729ndash3734 1995

[25] M Fleischmann G Sundholm and Z Q Tian ldquoAn SERSstudy of silver electrodeposition from thiourea and cyanidecontaining solutionsrdquo Electrochimica Acta vol 31 no 8 pp907ndash916 1986

[26] W Vielstich and H Gerischer ldquoZur elektrolyse bei konstantemelektrodenpotentialrdquo Zeitschrift fur Physikalische Chemie vol 3no 1-2 pp 16ndash33 1955

[27] H Sanchez E Chainet B Nguyen P Ozil and Y Meas ldquoElec-trochemical deposition of silver from a low cyanide concentra-tion bathrdquo Journal of the Electrochemical Society vol 143 no 9pp 2799ndash2815 1996

[28] G Baltrunas ldquoThe mechanism of electrode process in the sys-tem silversilver cyanide complexesrdquo Electrochimica Acta vol48 no 24 pp 3659ndash3664 2003

[29] R Morrissey ldquoGold and silver plating basics an overview ofprecious metal electroplating processesrdquo Products Finishing2011

[30] A J Bard and L R Faulkner Electrochemical Methods StudentSolutions Manual Fundamentals and Applications John Wileyamp Sons 2002

[31] D G Foster Y Shapir and J Jorne ldquoThe effect of rate of surfacegrowth on roughness scalingrdquo Journal of the ElectrochemicalSociety vol 152 no 7 pp C462ndashC465 2005

[32] Y M Kolotyrkin ldquoEffect of specific adsorption of anions onhydrogen overvoltagerdquo Transactions of the Faraday Society vol55 pp 455ndash462 1959

[33] G Senanayake ldquoThe cyanidation of silver metal review ofkinetics and reaction mechanismrdquoHydrometallurgy vol 81 no2 pp 75ndash85 2006

[34] J Li and M E Wadsworth ldquoElectrochemical study of silverdissolution in cyanide solutionsrdquo Journal of the ElectrochemicalSociety vol 140 no 7 pp 1921ndash1927 1993

[35] J B Hiskey andVM Sanchez ldquoMechanistic and kinetic aspectsof silver dissolution in cyanide solutionsrdquo Journal of AppliedElectrochemistry vol 20 no 3 pp 479ndash487 1990

[36] H Swanson and E Tatge ldquoStandard X-ray diffraction patternsrdquoJournal of Research of the National Bureau of Standards vol 46no 4 p 318 1951

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


also improve the roughness and inhomogeneity of coatingsbecause of their good throwing power thus producing con-sistently high quality of white or bright deposits [14 15]Solutions with high throwing power are favorable in theplating process because they ensure uniform deposit onplated parts especially on those with complex geometries aswell as uneven current distribution

On the other hand cyanide-free silver plating solutionsoften make use of the weak chelating agent which only formsweak complexeswith themetallic impurities As a result poorsilver deposits are always formed in aging cyanide-free silverplating solutions as these metallic impurities are codepositedwith silver The weak silver complex formed in cyanide-freesilver plating solutions also increased the activity of free Agions which facilitates the displacement reactions betweensubstrate and silver ions releasing more metallic impuritiesinto the plating solutions

As a consequence manufacturers still tend to stay withcyanide-based solutions due to their high bath stability easeof operation and consistently high quality of silver coat-ings Implementing cyanide-free plating solutions in manu-facturing industries remains a great challenge [9]

Electrodeposited silver has been playing important rolesin decorative applications and electronics industries for dec-ades In response to the high demands in advanced electron-ics products good quality silver plating at high speed hasbecome a critical step in the manufacturing process More-over new applications in electronics and semiconductorindustries have also encouraged the development of newsilver chemistries for high speed selective plating such asmirror bright silver spot plating on leadframes

Similar to conventional alkaline silver electrolytes highspeed silver plating solutions usually have high potassiumcyanide content (45ndash100 gL) and are not suitable for selectiveor spot plating [16] In high speed silver spot plating onleadframes the leadframes are plated with silver to give abondable area on the lead finger to allow a second bond toform subsequently This area must be slightly larger than thesize of the second bond Insoluble anodes such as platinisedtitanium mesh or platinum wire are commonly used as onlythe tip of the lead finger is plated for bonding [17] Oxidationand polymerization of cyanide [18] at these insoluble anodeshave caused rapid degradation of the high cyanide silverplating solutions

Hence it would be desirable if the negative effect ofcyanide is minimized while at the same time the high qualityof silver coatings could be maintained consistently Besidesthat because of the low cyanide content the accumulation ofcarbonates could be slowed down As a consequence the lowcyanide silver bath life could also be extended

In this work the silver electrochemical processes insolutions consisting of a much lower amount of free cyanide(lt10 gL KCN) than the conventional alkaline silver elec-trolytes were first explored by using cyclic voltammetrictechnique The electrochemical behaviors and effects ofthe basic electrolytes (silver salt potassium cyanide andconducting salt) and solution pH on the electrodepositionand dissolution processes were also investigated In addition

the optimum working conditions for high speed silver elec-trodeposition in low cyanide system were also proposed

In order to ensure the feasibility of replacing high cyanidewith low cyanide system in practical applications the charac-teristics such as morphologies purity brightness conductiv-ity and hardness of Ag films electrodeposited by low cyanidesystem will also be compared with those electrodeposited byconventional high cyanide silver solution

2 Materials and Methods

21 Chemicals and Plating Conditions Chemicals used werepotassium silver (I) cyanide (KAg(CN)

2) potassium nitrate

(KNO3) potassium cyanide (KCN) nitric acid (HNO

3) and

potassium hydroxide (KOH) All solutions were preparedwith deionized water The pH of the solution was adjusted byusing either 1 HNO

3or 1 KOH solutions

Brass hull cell panel was used as a substrate for silverelectrodeposition All the pretreatment Ni and Ag electrode-position chemicals used are proprietary products providedby MacDermid Enthone Before deposition the brass wascleaned in the Enprep 110 EC Enprep 220 EC and Actane345 After that the brass was electrodeposited with a layer ofnickel (2-3 120583m) by usingHeliofabNi-370 Next a thin layer ofAg was electrodeposited on the Nibrass panel by using twotypes of silver solutions that is low cyanide silver solutionand conventional high cyanide silver solution The low cya-nide silver solution was made up of 120 gL KAg(CN)

2

6 gL KCN 120 gL KNO3 5mLL XRD Ag-7000 B1 and

16mLL XRD Ag-7000 B2 while the high cyanide silversolution consisted of 100 gL KAg(CN)

2 150 gL KCN 6 gL

KOH 20 gL K2CO3 5mLL Heliofab Ag-900 C and T and

3mLL Heliofab Ag-900 HThe electrodeposition conditionsfollowed the optimum parameters as recommended in theXRD Ag-7000 and Heliofab Ag-900 technical datasheetsThe pH values of the freshly prepared silver solutions wereadjusted to about 10ndash12 for both low and conventional highcyanide solutions

The current densities used for the electrodeposition are06 Acm2 for low cyanide system and 003Acm2 for con-ventional high cyanide system The deposition time of thetwo systems was adjusted so that the Ag films had a similarthickness at 20ndash25 120583m

22 Cyclic Voltammetric Analysis The electrochemical stud-ies of silver electrodeposition anddissolutionwere performedin a conventional three-electrode cell using computerizedpotentiostat (797VA Computrace Metrohm) at room tem-perature Polished platinum rotating disk (Metrohm 119860 =00314 cm2) was used as the working electrode During theexperiments AgAgCl (3M KCl) reference electrode wasmounted in an electrolyte vessel filled with 1M KNO

3solu-

tion and used as a double junction reference electrode Allthe potential measured in the voltammetric study referred tothis reference electrode A platinum rod which representedthe insoluble anode in industrial practice was employed asthe counter electrode All the silver electrodeposition anddissolution processes were studied at angular speed (120596) of1200 rpm The cyclic voltammetry scan rate was 50mVsminus1



3solution and 10



120572






2 KNO

3




3and KCN












Ag(CN)2



2

minus


Ag(CN)2


AgCN 999447999472 Ag+ + CNminus (3)

Ag+ + eminus 999447999472 Ag (4)



C1

C2

A1A2

C3



minus70

minus50

minus30

minus10

10

30

i(m

A cm

minus2 )


(a)

C1C2

A1


minus70

minus50

minus30

minus10

10

30

i(m

A cm

minus2 )


(b)


minus70

minus50

minus30

minus10

10

30

50

minus09Vminus10V

minus07Vminus08V

i(m

A cm

minus2 )

(c)




3solutions Arrows



2

minus Ag(CN)3

2minus and Ag(CN)4



2










minus50

minus40

minus30

minus20

minus10

0

10

20

30

60gL80gL

120 gL

140 gL160 gL180 gL200 gL

100gL

i(m

A cm

minus2 )

minus1012345678

i(m

A cm

minus2 )


E (V)

(a)

70 90 110 130 150 170 190 21050KAg(CN)2 (gLminus1)

minus071

minus070

minus069

minus068

minus067

minus066

minus065

minus064

minus063

minus062

E (V

)(b)

80 100 120 140 160 180 200 22060KAg(CN)2 (gLminus1)

000

100

200

300

400

500

600

700

800

900

Dep

ositi

on ra

te (120583

m m

inminus

1 )

(c)





2




119865120588Ag119860119905times 104(120583mmin) (6)



2



2concentration has






2


3


2


Ag+ + CNminus 999447999472 AgCN (7)

Ag+ + 2CNminus 999447999472 Ag(CN)2

minus (8)

Ag(CN)2


3

2minus (9)

Ag(CN)3


4

3minus (10)


2




2and 120 gL KNO

3



E (V

)

102 3 4 5 6 7 8 910

KCN (gLminus1)

140120100 160 180604020 800KCN (gLminus1)

minus105

minus095

minus085

minus075

minus065

minus055

minus045

minus035

minus025

E (V

)


2 120 gL KNO




2and KNO















3 K+





3






0gL30gL60gL90gL

120 gL150gL180gL


010203040

i(m

A cm

minus2 )

(a)

200

300

400

500

600

700

800

900

1000

Dep

ositi

on ra

te (120583

m m

inminus

1 )

30 60 90 120 150 1800KNO3 (gLminus1)

(b)





to minus07 V

pH 80pH 85pH 90pH 95pH 100

pH 105pH 110pH 115pH 120


minus40

minus30

minus20

minus10

0

10

20

30

i(m

A cm

minus2 )

(a)

85 9 95 10 105 11 115 128pH

minus070

minus065

minus060

minus055

minus050

E(V

) ver

sus A

gA

gCl (3

M K

Cl)

(b)




















2(119887)+ eminus (11)



minus10Vminus09V

minus11V

minus12Vminus13V


minus200

minus150

minus100

minus50

0

50

100

150

200

i(m

A cm

minus2 )


2 and










00

100

200

300

400

500

600

700

800876

(nm

)

Ra = 88nm

(c)

00

100

200

300

400

500

600

700

800

900

10001055

(nm

)

Ra = 98nm

(d)(d)


Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(a)

Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(b)




005 On the other


4 Conclusion





Ag3dS2pO1sC1s

Ag3dS2pO1sC1s

Low CN High CN

10 20 30 40 50 60 70 80 900Depth (nm)

00

200

400

600

800

1000

Atom

ic p

erce

nt (

)



3lowers the




Competing Interests


Acknowledgments


References

















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



3solution and 10



120572






2 KNO

3




3and KCN












Ag(CN)2



2

minus


Ag(CN)2


AgCN 999447999472 Ag+ + CNminus (3)

Ag+ + eminus 999447999472 Ag (4)



C1

C2

A1A2

C3



minus70

minus50

minus30

minus10

10

30

i(m

A cm

minus2 )


(a)

C1C2

A1


minus70

minus50

minus30

minus10

10

30

i(m

A cm

minus2 )


(b)


minus70

minus50

minus30

minus10

10

30

50

minus09Vminus10V

minus07Vminus08V

i(m

A cm

minus2 )

(c)




3solutions Arrows



2

minus Ag(CN)3

2minus and Ag(CN)4



2










minus50

minus40

minus30

minus20

minus10

0

10

20

30

60gL80gL

120 gL

140 gL160 gL180 gL200 gL

100gL

i(m

A cm

minus2 )

minus1012345678

i(m

A cm

minus2 )


E (V)

(a)

70 90 110 130 150 170 190 21050KAg(CN)2 (gLminus1)

minus071

minus070

minus069

minus068

minus067

minus066

minus065

minus064

minus063

minus062

E (V

)(b)

80 100 120 140 160 180 200 22060KAg(CN)2 (gLminus1)

000

100

200

300

400

500

600

700

800

900

Dep

ositi

on ra

te (120583

m m

inminus

1 )

(c)





2




119865120588Ag119860119905times 104(120583mmin) (6)



2



2concentration has






2


3


2


Ag+ + CNminus 999447999472 AgCN (7)

Ag+ + 2CNminus 999447999472 Ag(CN)2

minus (8)

Ag(CN)2


3

2minus (9)

Ag(CN)3


4

3minus (10)


2




2and 120 gL KNO

3



E (V

)

102 3 4 5 6 7 8 910

KCN (gLminus1)

140120100 160 180604020 800KCN (gLminus1)

minus105

minus095

minus085

minus075

minus065

minus055

minus045

minus035

minus025

E (V

)


2 120 gL KNO




2and KNO















3 K+





3






0gL30gL60gL90gL

120 gL150gL180gL


010203040

i(m

A cm

minus2 )

(a)

200

300

400

500

600

700

800

900

1000

Dep

ositi

on ra

te (120583

m m

inminus

1 )

30 60 90 120 150 1800KNO3 (gLminus1)

(b)





to minus07 V

pH 80pH 85pH 90pH 95pH 100

pH 105pH 110pH 115pH 120


minus40

minus30

minus20

minus10

0

10

20

30

i(m

A cm

minus2 )

(a)

85 9 95 10 105 11 115 128pH

minus070

minus065

minus060

minus055

minus050

E(V

) ver

sus A

gA

gCl (3

M K

Cl)

(b)




















2(119887)+ eminus (11)



minus10Vminus09V

minus11V

minus12Vminus13V


minus200

minus150

minus100

minus50

0

50

100

150

200

i(m

A cm

minus2 )


2 and










00

100

200

300

400

500

600

700

800876

(nm

)

Ra = 88nm

(c)

00

100

200

300

400

500

600

700

800

900

10001055

(nm

)

Ra = 98nm

(d)(d)


Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(a)

Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(b)




005 On the other


4 Conclusion





Ag3dS2pO1sC1s

Ag3dS2pO1sC1s

Low CN High CN

10 20 30 40 50 60 70 80 900Depth (nm)

00

200

400

600

800

1000

Atom

ic p

erce

nt (

)



3lowers the




Competing Interests


Acknowledgments


References

















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


C1

C2

A1A2

C3



minus70

minus50

minus30

minus10

10

30

i(m

A cm

minus2 )


(a)

C1C2

A1


minus70

minus50

minus30

minus10

10

30

i(m

A cm

minus2 )


(b)


minus70

minus50

minus30

minus10

10

30

50

minus09Vminus10V

minus07Vminus08V

i(m

A cm

minus2 )

(c)




3solutions Arrows



2

minus Ag(CN)3

2minus and Ag(CN)4



2










minus50

minus40

minus30

minus20

minus10

0

10

20

30

60gL80gL

120 gL

140 gL160 gL180 gL200 gL

100gL

i(m

A cm

minus2 )

minus1012345678

i(m

A cm

minus2 )


E (V)

(a)

70 90 110 130 150 170 190 21050KAg(CN)2 (gLminus1)

minus071

minus070

minus069

minus068

minus067

minus066

minus065

minus064

minus063

minus062

E (V

)(b)

80 100 120 140 160 180 200 22060KAg(CN)2 (gLminus1)

000

100

200

300

400

500

600

700

800

900

Dep

ositi

on ra

te (120583

m m

inminus

1 )

(c)





2




119865120588Ag119860119905times 104(120583mmin) (6)



2



2concentration has






2


3


2


Ag+ + CNminus 999447999472 AgCN (7)

Ag+ + 2CNminus 999447999472 Ag(CN)2

minus (8)

Ag(CN)2


3

2minus (9)

Ag(CN)3


4

3minus (10)


2




2and 120 gL KNO

3



E (V

)

102 3 4 5 6 7 8 910

KCN (gLminus1)

140120100 160 180604020 800KCN (gLminus1)

minus105

minus095

minus085

minus075

minus065

minus055

minus045

minus035

minus025

E (V

)


2 120 gL KNO




2and KNO















3 K+





3






0gL30gL60gL90gL

120 gL150gL180gL


010203040

i(m

A cm

minus2 )

(a)

200

300

400

500

600

700

800

900

1000

Dep

ositi

on ra

te (120583

m m

inminus

1 )

30 60 90 120 150 1800KNO3 (gLminus1)

(b)





to minus07 V

pH 80pH 85pH 90pH 95pH 100

pH 105pH 110pH 115pH 120


minus40

minus30

minus20

minus10

0

10

20

30

i(m

A cm

minus2 )

(a)

85 9 95 10 105 11 115 128pH

minus070

minus065

minus060

minus055

minus050

E(V

) ver

sus A

gA

gCl (3

M K

Cl)

(b)




















2(119887)+ eminus (11)



minus10Vminus09V

minus11V

minus12Vminus13V


minus200

minus150

minus100

minus50

0

50

100

150

200

i(m

A cm

minus2 )


2 and










00

100

200

300

400

500

600

700

800876

(nm

)

Ra = 88nm

(c)

00

100

200

300

400

500

600

700

800

900

10001055

(nm

)

Ra = 98nm

(d)(d)


Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(a)

Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(b)




005 On the other


4 Conclusion





Ag3dS2pO1sC1s

Ag3dS2pO1sC1s

Low CN High CN

10 20 30 40 50 60 70 80 900Depth (nm)

00

200

400

600

800

1000

Atom

ic p

erce

nt (

)



3lowers the




Competing Interests


Acknowledgments


References

















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



minus50

minus40

minus30

minus20

minus10

0

10

20

30

60gL80gL

120 gL

140 gL160 gL180 gL200 gL

100gL

i(m

A cm

minus2 )

minus1012345678

i(m

A cm

minus2 )


E (V)

(a)

70 90 110 130 150 170 190 21050KAg(CN)2 (gLminus1)

minus071

minus070

minus069

minus068

minus067

minus066

minus065

minus064

minus063

minus062

E (V

)(b)

80 100 120 140 160 180 200 22060KAg(CN)2 (gLminus1)

000

100

200

300

400

500

600

700

800

900

Dep

ositi

on ra

te (120583

m m

inminus

1 )

(c)





2




119865120588Ag119860119905times 104(120583mmin) (6)



2



2concentration has






2


3


2


Ag+ + CNminus 999447999472 AgCN (7)

Ag+ + 2CNminus 999447999472 Ag(CN)2

minus (8)

Ag(CN)2


3

2minus (9)

Ag(CN)3


4

3minus (10)


2




2and 120 gL KNO

3



E (V

)

102 3 4 5 6 7 8 910

KCN (gLminus1)

140120100 160 180604020 800KCN (gLminus1)

minus105

minus095

minus085

minus075

minus065

minus055

minus045

minus035

minus025

E (V

)


2 120 gL KNO




2and KNO















3 K+





3






0gL30gL60gL90gL

120 gL150gL180gL


010203040

i(m

A cm

minus2 )

(a)

200

300

400

500

600

700

800

900

1000

Dep

ositi

on ra

te (120583

m m

inminus

1 )

30 60 90 120 150 1800KNO3 (gLminus1)

(b)





to minus07 V

pH 80pH 85pH 90pH 95pH 100

pH 105pH 110pH 115pH 120


minus40

minus30

minus20

minus10

0

10

20

30

i(m

A cm

minus2 )

(a)

85 9 95 10 105 11 115 128pH

minus070

minus065

minus060

minus055

minus050

E(V

) ver

sus A

gA

gCl (3

M K

Cl)

(b)




















2(119887)+ eminus (11)



minus10Vminus09V

minus11V

minus12Vminus13V


minus200

minus150

minus100

minus50

0

50

100

150

200

i(m

A cm

minus2 )


2 and










00

100

200

300

400

500

600

700

800876

(nm

)

Ra = 88nm

(c)

00

100

200

300

400

500

600

700

800

900

10001055

(nm

)

Ra = 98nm

(d)(d)


Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(a)

Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(b)




005 On the other


4 Conclusion





Ag3dS2pO1sC1s

Ag3dS2pO1sC1s

Low CN High CN

10 20 30 40 50 60 70 80 900Depth (nm)

00

200

400

600

800

1000

Atom

ic p

erce

nt (

)



3lowers the




Competing Interests


Acknowledgments


References

















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



2


3


2


Ag+ + CNminus 999447999472 AgCN (7)

Ag+ + 2CNminus 999447999472 Ag(CN)2

minus (8)

Ag(CN)2


3

2minus (9)

Ag(CN)3


4

3minus (10)


2




2and 120 gL KNO

3



E (V

)

102 3 4 5 6 7 8 910

KCN (gLminus1)

140120100 160 180604020 800KCN (gLminus1)

minus105

minus095

minus085

minus075

minus065

minus055

minus045

minus035

minus025

E (V

)


2 120 gL KNO




2and KNO















3 K+





3






0gL30gL60gL90gL

120 gL150gL180gL


010203040

i(m

A cm

minus2 )

(a)

200

300

400

500

600

700

800

900

1000

Dep

ositi

on ra

te (120583

m m

inminus

1 )

30 60 90 120 150 1800KNO3 (gLminus1)

(b)





to minus07 V

pH 80pH 85pH 90pH 95pH 100

pH 105pH 110pH 115pH 120


minus40

minus30

minus20

minus10

0

10

20

30

i(m

A cm

minus2 )

(a)

85 9 95 10 105 11 115 128pH

minus070

minus065

minus060

minus055

minus050

E(V

) ver

sus A

gA

gCl (3

M K

Cl)

(b)




















2(119887)+ eminus (11)



minus10Vminus09V

minus11V

minus12Vminus13V


minus200

minus150

minus100

minus50

0

50

100

150

200

i(m

A cm

minus2 )


2 and










00

100

200

300

400

500

600

700

800876

(nm

)

Ra = 88nm

(c)

00

100

200

300

400

500

600

700

800

900

10001055

(nm

)

Ra = 98nm

(d)(d)


Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(a)

Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(b)




005 On the other


4 Conclusion





Ag3dS2pO1sC1s

Ag3dS2pO1sC1s

Low CN High CN

10 20 30 40 50 60 70 80 900Depth (nm)

00

200

400

600

800

1000

Atom

ic p

erce

nt (

)



3lowers the




Competing Interests


Acknowledgments


References

















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



0gL30gL60gL90gL

120 gL150gL180gL


010203040

i(m

A cm

minus2 )

(a)

200

300

400

500

600

700

800

900

1000

Dep

ositi

on ra

te (120583

m m

inminus

1 )

30 60 90 120 150 1800KNO3 (gLminus1)

(b)





to minus07 V

pH 80pH 85pH 90pH 95pH 100

pH 105pH 110pH 115pH 120


minus40

minus30

minus20

minus10

0

10

20

30

i(m

A cm

minus2 )

(a)

85 9 95 10 105 11 115 128pH

minus070

minus065

minus060

minus055

minus050

E(V

) ver

sus A

gA

gCl (3

M K

Cl)

(b)




















2(119887)+ eminus (11)



minus10Vminus09V

minus11V

minus12Vminus13V


minus200

minus150

minus100

minus50

0

50

100

150

200

i(m

A cm

minus2 )


2 and










00

100

200

300

400

500

600

700

800876

(nm

)

Ra = 88nm

(c)

00

100

200

300

400

500

600

700

800

900

10001055

(nm

)

Ra = 98nm

(d)(d)


Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(a)

Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(b)




005 On the other


4 Conclusion





Ag3dS2pO1sC1s

Ag3dS2pO1sC1s

Low CN High CN

10 20 30 40 50 60 70 80 900Depth (nm)

00

200

400

600

800

1000

Atom

ic p

erce

nt (

)



3lowers the




Competing Interests


Acknowledgments


References

















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of













2(119887)+ eminus (11)



minus10Vminus09V

minus11V

minus12Vminus13V


minus200

minus150

minus100

minus50

0

50

100

150

200

i(m

A cm

minus2 )


2 and










00

100

200

300

400

500

600

700

800876

(nm

)

Ra = 88nm

(c)

00

100

200

300

400

500

600

700

800

900

10001055

(nm

)

Ra = 98nm

(d)(d)


Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(a)

Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(b)




005 On the other


4 Conclusion





Ag3dS2pO1sC1s

Ag3dS2pO1sC1s

Low CN High CN

10 20 30 40 50 60 70 80 900Depth (nm)

00

200

400

600

800

1000

Atom

ic p

erce

nt (

)



3lowers the




Competing Interests


Acknowledgments


References

















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


00

100

200

300

400

500

600

700

800876

(nm

)

Ra = 88nm

(c)

00

100

200

300

400

500

600

700

800

900

10001055

(nm

)

Ra = 98nm

(d)(d)


Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(a)

Inte

nsity

(au

)

20 30 40 50 60 70 80102120579 (∘)

(111

)

(200

)

(220

)

(311

)

(b)




005 On the other


4 Conclusion





Ag3dS2pO1sC1s

Ag3dS2pO1sC1s

Low CN High CN

10 20 30 40 50 60 70 80 900Depth (nm)

00

200

400

600

800

1000

Atom

ic p

erce

nt (

)



3lowers the




Competing Interests


Acknowledgments


References

















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Ag3dS2pO1sC1s

Ag3dS2pO1sC1s

Low CN High CN

10 20 30 40 50 60 70 80 900Depth (nm)

00

200

400

600

800

1000

Atom

ic p

erce

nt (

)



3lowers the




Competing Interests


Acknowledgments


References

















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

research article cyclic voltammetric study of high speed...

Documents