research article electroreduction of copper dichloride powder to copper...

Research ArticleElectroreduction of Copper Dichloride Powder to CopperNanoparticles in an Ionic Liquid

Tian Wu1 Qing Huang1 Wei Li2 Gongxuan Chen1 Xiaoling Ma1 and Guoping Zeng1

1 College of Chemistry and Life Science Hubei University of Education Wuhan 430205 China2Department of Rare Metals Guangzhou Research Institute of Non-ferrous Metals Guangzhou 510650 China

Correspondence should be addressed to Tian Wu twuwhueducn and Xiaoling Ma 240200025qqcom

Received 11 November 2013 Accepted 20 December 2013 Published 6 February 2014

Academic Editor Hui Xia

Copyright copy 2014 Tian Wu et alThis is an open access article distributed under the Creative Commons Attribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

There were a large number of ionic liquids electrodeposition reported in the literature but were still in the laboratory stage someproblems in the practical application of electrodeposition remain such as easily reacted with moisture in the air (AlCl

3ionic

liquid) high cost and corrosive (dialkylimidazolium cation and BF4minus PF6

minus ionic liquid) In addition to the above shortcomingslow solubility of many metal salts in ionic liquids limits the practical application In order to solve the problem of low solubility[Bmim]Cl could be added [Bmim]PF

6 which could significantly increase the solubility of metal chlorides this method could

be commonly used in preparing metal electrochemical reduction of metal chlorides Our study showed that adding cationicgroups in hydroxyl ionic liquid could cause the good solubility of transition metal chlorides such as CuCl

2 Complexation of

hydroxyl functional group and transitionmetal ions increased solubility resulting in a larger deposition current density and surfaceelectrochemical reduction of copper nanoparticles deposited on the metal Ni The electroreduction mechanism and behavior ofCuCl2in hydroxyl ionic liquid and the Cu nanoparticle formation mechanism were investigated based on a comparison between

similar experiments in the ionic liquid

1 Introduction

Electrolytic metal electrodeposition method refers to a solidsurface in the process to obtain the deposited metal layer Itaims for the following areas the refining of themetalmaterialthe surface characteristics changing of the solid materialand the preparation of a specific component of metal orsemiconductor materials Generally metal electrodepositionincludes electrolytic smelting electroforming and platingAs an electrochemical deposition medium the application ofaqueous solution was restricted by electrochemical windowof water while conventional molten salt is generally limitedby high temperature and energy consumption Comparedwith others ionic liquids have thermal stability nonvolatilenonflammable moderate conductivity and wide electro-chemical window nature and could compensate for the lackof water and molten salts [1 2] Moreover most of themetal deposited in the aqueous solution can be generatedin ionic liquids and some light metals refractory metalsand semiconductor materials can only be obtained in ionic

liquids at room temperature which could not get in aqueousdeposition Furthermore the addition ofmany toxic agents inthe conventional electroplating could generally be consideredas a high environmental pollution industry In ionic liquidsfor electroplating it is no need to add in substances forsuppression of hydrogen evolution and even toxic additivesTherefore there is a hope for ionic liquids to become a kindof important green electrolyte in electrochemical preparationof metal semiconductor materials and electroplating [3]

Murase et al [4] studied the oxidation-reduction ofelectrodeposition of copper in TMHA-Tf2N ionic liquidsthis process involves the reaction of Cu + Cu2+ rarr 2Cu+Finally to obtain electrodeposition of copper on the cathodethe deposition process current efficiency of single-electronreaction reached almost 100 Chen and Sun [5] reportedthat copper was electrodeposited on polycrystalline tungstenelectrode platinum electrode and a glassy carbon electrodein tetrafluoroborate 1-ethyl-3-methyl imidazole (EMIC-BF

4)

ionic liquids which joined the cuprous chloride increasethe solubility of CuCl Cu+ could be oxidized to Cu2+ or

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2014 Article ID 751424 6 pageshttpdxdoiorg1011552014751424

2 Journal of Nanomaterials

reduced to metallic copper CuCu+ redox demonstrated aquasireversible charge transfer process

Endres and Schweizer [6] studied the electrodepositionof copper on Au (111) as the matrix at different temperaturesin trifluoromethanesulfonate imide 1-butyl-1-methylpyridine(BMPy-Tf

2N) ionic liquid and sediment layers was observed

using a scanning tunneling electronmicroscopy Experimen-tal results showed that the majority of the copper compoundin ionic liquids has low solubility the anodic dissolutioncould increase copper ions in the solution Study found thatthe curve showed a consistent feature andwith the increase oftemperature and current of copper the deposition potentialbecomes more positive

Although there a large number of electrodepositionbehavior of ionic liquids was reported in the literature [7ndash11] while most of them were still in the laboratory stagethe practical application of electrodeposition still has someproblems such as AlCl

3ionic liquid which can easily react

with moisture in the air and should be operated in the glovebox ionic liquid is constituted of dialkyl imidazolium cationand BF

4

minus PF6

minus although the stability is improved the costwas high and could be corrosive when placed it for a longtime In addition the low solubility of the metal salts in ionicliquids also limits the practical application

Following the successful electrochemical reduction ofsolid metal oxides to the metals in high temperature moltensalts [12ndash14] solid CuO nanoparticles were electroreduced tocopper nanoparticles in an aqueous electrolyte aiming forcatalytic applications [14]

In order to solve the problem of low solubility [Bmim]Cl can be added to [Bmim] PF

6 which can significantly

increase the solubility ofmetal chlorides themethod could becommonly used in electrochemical reduction of metal frommetal chlorides

Ionic liquids usually contain functional groups and couldbe divided into functional ionic liquids and conventionalionic liquids Function ionic liquid (task-specific ionic liquidabbreviated as TSIL) has a specific group introduced intothe structure which was provided with a unique functionFor example cuprous chloride and cupric chloride wererecently reported having a good solubility in 1-ethyl-3-methylimidazolium dicyanamide ionic liquid which may bedue to the complexation of dicyandiamide anion At thesame time electrochemical behavior of nickel chloride wasalso studied in such ionic liquid [15] The emergence offunctionalized ionic liquids enriches the types of ionic liquidsand leads the direction of the development of ionic liquids[16] Functionalized ionic liquids (FILs) containing alcoholon the alkyl arms have receivedmuch attention in the fields oforganic synthesis and catalysis Compared to traditional ILsthey show additional advantages such as alterable polaritylower viscosity and higher solubility for inorganic salts[17 18] Since the OH group has the positive effect onthe solubility this idea can extend to the correspondinghydroxyl-functionalized ionic liquids (HFILs) directly for theincreasing solubility of CuCl

2without using other additives

The solubility of transition metal halides can be increased byusing cations that are capable of forming complex ions withtransition metals In view of the good donor ligand property

that is known for the hydroxyl group transition metalcompounds should be soluble in the hydroxyl-functionalizedionic liquids (HFILs) and the preparation of a bath solutionfor electrodeposition is possible

Although HFILs may be potentially useful electrolytesexamples using these RTILs for metal electrodeposition arevery limited In order to evaluate the utility of this new RTILsystem the electrochemistry and electrodeposition of copperin theHFILs were studied in this workThe voltammetric andnucleation behavior of copper electrodeposition at Pt and Nielectrodes respectively were studied (see Figure 5)Hydroxylfunctional group and transition metal ions complexationincreased the solubility resulting in a larger depositioncurrent density and surface electrochemical reduction ofnanocopper particles deposited on metal Ni And redoxbehavior of copper ions of CuCl

2in hydroxyl ionic liquid

was different from the reported two single-electron redoxbehavior three oxidation peaks was found in our experimentand the cause of the third oxidation peak were also analyzedElectrodeposits of copper were prepared using controlledpotential electrolysis at copper substrates and examined byscanning electron microscopy (SEM)

2 Experimental

21 Instruments and Reagents The preparation and charac-terisation of 1-butyl-3-metylimidizolium chloride ([BMIM]Cl viscous liquid) and hexafluorophosphate ([BMIM] PF

6

liquid) followed the literature description [19 20] The pow-ders of cuprous chloride (CuCl gt97) and CuCl

2(99

Acros Organics) were thermally dried in vacuum beforeuse The solubility of these dried salts in [BMIM] PF

6was

measured as followsThe IL was first saturated with an excessamount of the salt at 80∘C under stirring for 48 h Afterstanding still for over 24 h the clear solution was sampledat different temperatures (80∘C 60∘C 40∘C and 28∘C) Thesample was treated with concentrated H

2SO4and H

2O2

and then diluted in double-distilled water before analysisby atomic absorption spectrometer (AAnalyst800 PerkinElmer)

Electrochemical workstation Shanghai CH InstrumentCompany Chi 660A Superheated tank Shanghai Exper-imental Instrument Factory ZKF030 Working electrode100 120583m Pt plate 07mm Cu plate 2mm times 5mmNi tabletsauxiliary electrode 6mm times 4mm Pt films 6mm times 3mmCutablets reference electrode AgAg+ electrode Electrolyzerlaminated glass structure adding ionic liquid volume ofapproximately 1mL with airway and seals

The electrolytic products from the IL were washed withacetonitrile twice dried in vacuum and analysed directlyby X-ray diffraction spectroscopy (XRD SHIMADZU X-ray6000 with Cu-K120572) and scanning electron microscopy (SEMHITACHIx-650)

22 Making Reference Electrode AgPF6was dissolved in

BMIMPF6 allowing the theoretical content of Ag+ to be

30Mm a silver lining will be inserted into the solution andseparated with the outer layer ionic liquid BMIMPF6 salt

Journal of Nanomaterials 3

0 1 2 3

05

00

minus05

minus10

minus15

minus20

minus2 minus1

Curr

ent d

ensit

y (m

A cm

minus2)

Voltage (versus AgAg+)

Figure 1 Cyclic voltammograms of a Pt-disk electrode (diameter100120583m) recorded under ambient conditions after addition of excessCuCl2powder in the BMIMPF

6and standing for 1 h

bridge with alumina ceramic then inserting secondary jacketinto ion liquid

23 Electrochemical Test Program Ionic liquids were driedat 70∘C 12 h in vacuum prior to the electrochemical testanhydrous cuprous chloride and cupric chloride were usedwithout further processing The copper ionic liquid wasadded and stirred under argon through circulating thewater temperature to the required test temperature All theelectrochemical tests should maintain the liquid level in theargon atmosphere

Cyclic voltammetry tests were performed in a three-electrode system AgAg+ was selected as the referenceelectrode a large area platinum sheet as counter electrodea platinum plate copper plate and nickel plate as workingelectrode respectively

24 Constant Potential Electrolysis A large area of copperwastaken as the counter electrode the working electrode wasa nickel plate or copper plate Powder on the nickel sheetsamples were deposited with distilled water and acetone thendried and prepared as samples for SEM morphology imageanalysis

3 Results and Discussion

31 Electrochemical Behavior of CuCl2

in Ionic LiquidsBMIMPF

6 Electrochemical window of BMIMPF6 in an

argon gas atmosphere was about 41 V no impurity peakswere found After adding CuCl

2 the mixture was stirred

with BMIMPF6at 40∘C 1 h and divalent copper ions were

detected with electrochemical method in the system Asshown in Figure 1 the current peaks can be attributed toelectrochemical conversion between these Cu Cu+ andCu2+ ions The quasireversible redox couple at about 05 V(versus AgAg+) was represented to the reaction Cu2+ + e999448999471 Cu+ The oxidation peak of minus06V below potential ofminus08V corresponds to metallic copper reoxidation on the

minus20 minus15 minus10 minus05 00 05 10 15

0

1

2

3

4

5

minus1

minus2

minus3

First cycle

Second cycle

BackgroundCurr

ent d

ensit

y (m

A cm

minus2)


Figure 2 Cyclic voltammograms of a Pt-disk electrode (diameter100 120583m) recorded under ambient conditions after addition of excessCuCl2powder in the C

3OHmimBF

4and standing for 1 h at 60∘C

Potential scan rate 50mVsminus1

platinum electrode It is noted that current density at 15 Vwas increasing due to the oxidation of dissolved chloride ionin the system

Compared with phenomena reported by Yu et al thatafter stirring CuCl overnight with BMIMPF

6 no Cu+ or Clminus

peaks were found in cyclic voltammetry we speculate thatthe solubility of CuCl

2in BMIMPF6 was larger than CuCl

comply with inference of solubility size measured by atomicabsorption spectrometry

32 Cyclic Voltammetric Behavior of C3OHmimBF

4CuCl

2

System After slight excess of CuCl2

was added toC3OHmimBF

4 copper ion concentration could be measured

by a weighing method to be about 40Mm After strongstirring for 1 hour and standing after a short time cyclicvoltammetry study of the system was shown in Figure 2 Thebehavior cyclic voltammetry was significantly different fromour previous observations of CuCl

2in BMIMPF6 Oxidation

of chloride ion in C3OHmimBF

4was carried out at a lower

electric potential of the oxidation reaction occurrence theoxidation peak significantly decreases to 10 V For cupricions and significantly different from the previously observedredox groups two reduction peaks and three oxidation peakswere observed respectivelyThe cause for the third oxidationpeak was the focus of our research Furthermore the peakcurrent density of both the chloride ions and copper ionswere significantly increased which was closely related togreater solubility of CuCl

2in C3OHmimBF

4

As the scan range of Figure 2 includes the oxidation ofchloride ions in order to avoid the influence of chlorideions to copper oxide interval between minus16 V and 04Vwas chosen for a separate scan as shown in Figure 3The systemrsquos open-circuit potential was at 01 V the reac-tions before the reduction peaks occurred as follows in01 Vsim minus05 V Cu2+ rarr Cu+ in minus1 Vsim minus16 V Cu+ rarr Cu(before the start of the reduction reaction the concentrationof chloride ion electrode surface was limited and there was


0

1

2

3

4

5

minus1

minus2

minus3

Curr

ent d

ensit

y (m

A cm

minus2)

minus20 minus15 minus10 minus05 00 05

a1

a2

a3

c1

c2


Figure 3 Cyclic voltammograms of a Pt-disk electrode (diameter100120583m) recorded under ambient conditions after addition of excessCuCl2powder in the C

3OHmimBF


Potential scan rate 50mVsminus1 Scanning range minus16 Vsim04V

10

0

minus10

minus20

minus30

minus40

minus18 minus16 minus14 minus12 minus10 minus08 minus06 minus04 minus02

a2a3

c2

c3

Curr

ent d

ensit

y (m

A cm

minus2)

Firstcycle



3OHmimBF

4and standing for 1 h at 60∘ C

Potential scan rate 50mVsminus1 Scanning range minus16 Vsim minus03 V

a lot of C3OHmim+ in the system so here changes of the

valence of copper ions are complexed of C3OHmin+ to form

hydroxy complexes) In order to determine the attribution ofthe respective redox peaks the interval between minus16sim minus03 Vwas shown in Figure 4 Figure 6 further confirmed the Cu +2to +1 transition between prices

In Figure 4 we have retraced the oxidation potential tominus03 V which was not readily oxidized to the peak positiona1 resulting in a significant change in the second week of asharp peak c3 which could be interpreted as Cu2+ scanningin the first week after the reduction of Cu and generated freechloride ion near the electrode which undergone a coppercompetition with a hydroxyl ligand system The product ofthe oxidation peak a3 was complexed with the hydroxyland Cu+ Soon afterwards further complexation for [Cu

Curr

ent d

ensit

y (m

A cm

minus2)

minus22 minus20 minus18 minus16 minus14 minus12 minus10 minus08 minus06 minus04

45403530252015100500

minus05minus10minus15minus20minus25minus30minus35minus40

40∘C80∘CBlank


Figure 5 Cyclic voltammograms of a Ni electrode recorded underambient conditions after addition of excess CuCl

2powder in the

C3OHmimBF

4Cl and standing at 60∘C and 80∘C Potential scan

rate 50mVsminus1 Scanning range minus16 Vsim04V

(C3OHmim-BF

4

minus)] and chloride ion around the electrodeoccurred And a3 and c3 constituted a group of chloride ionin the dissolution peak ligand as follows [Cu (C

3OHmim-

BF4

minus)] + Clminus(l)-e rarr [Cu (C3OHmim-BF

4

minus) Cl]+ Noting thechanges in the redox battery during the first week peak areasa3 was larger following in the second week of a sharp peak c3and the corresponding peak area a3was significantly reduced

33 Electrodeposition of Copper Chloride on Nickel Sheet


in theC3OHMIMBF

4Cl Reduction peak of the first cycle

which is more complex and may be present on the surface ofnickel electrode reduced oxidizing substances Subsequentcycles showed a set of simple redox peaks of copper ions inthe reduction behavior of nickel electrode on a platinumelectrode with a significant difference Only a bunch of redoxpeaks were observed represent cupric two-electron redoxprocess If rising the temperature copper-nickel electrodereduction peak current has been significant negative shiftedthe oxidation peak position basically unchanged It couldavoid oxidation which leads to excessive current positivenickel electrode oxidation We examined the reductionpotential temperature and reduction time on the productmorphology

332 SEM Figures of Products of Constant Potential Electrol-ysis in CuCl

2C3OHMIMBF

4Cl System SEM images of the

copper nanoparticles prepared by electro-reduction of theCuCl2powder on a Ni foil in C

3OHmimBF

4Cl at (a) minus17 V

80∘C 400 s (b)minus15 V 80∘C 400 s (c) minus17 V 40∘C 1200 sand (d) minus18 V 40∘C 1200 s (versus AgAg+) were shownin Figure 6 At 80∘C particles were approximately 50 nmand piled in large particle sizes ranging from about several


(a)

1120583m

(b)

(c)

500nm

(d)

Figure 6 SEM images of the copper nanoparticles prepared by electro-reduction of the CuCl2powder on a Ni foil in C

3OHmimBF

4Cl at

(a) minus17 V 80∘C 400 s (b) minus15 V 80∘C 400 s (c) minus17 V 40∘C 1200 s and (d) minus18 V 40∘C 1200 s (versus AgAg+)

hundred nanometers When the potential rose up to minus15 Vparticles were about 50 nm and piled in large particle sizeuniformity about 300 nm When deposition potentials weremore positive more uniform particles could be obtainedthe deposition layer was in smaller size When depositionpotential becomes negative the particle size becomes largerFigure 6(c) represented a figure large particle size decreases(the same deposition potential at different temperatures)Figures 6(c) and 6(d) showed that particle size increasedslightly compared with large particle size was relativelyuniform about 300 nmWhen the temperature of depositionwas lower smaller and more uniform deposited layer couldbe obtained

4 Summary

Our study shows that cationic group to add a hydroxyl-functionalized ionic liquids for the transition metal chlo-rides such as CuCl

2 has good solubility Complexation

between hydroxyl functional group and transition metal ionsincreased solubility resulting in a larger deposition currentdensity CuCl

2hydroxyl ions in the liquid redox behavior

of copper ions with the reported two single-electron redoxbehavior were different we got three oxidation peaks and thecause analysis of the third oxidation peak was made

The difference of nickel electrode CuCl2reduction behav-

ior in the platinum electrode was studied Only one pair ofredox peaks was observed on nickel electrode correspondingto divalent copper two-electron redox process Nanocopperparticles were electrochemically reduced and deposited on

the surface of metal Ni When deposition potential wasmore positive more uniform particles were obtained and thedeposition layer was in smaller size

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors acknowledge the financial support from theNational Natural Science Foundation of China (Grant nos21303045 and 51204060) the Hubei University of EducationKey Disciplines (Applied Chemistry) ldquoExcellent TeacherTeam Buildingrdquo Scientific Research Project of Hubei Uni-versity of Education (Grant no 2012K103) Open Fundof Key Laboratory of Hubei Province of Implantation ofAnticancer Active Substances Purification and Applicationand the Natural Science Foundation of Guangdong Province(no S2012040007501)

References

[1] PWasserscheid and TWelton Ionic Liquids in SynthesisWiley-VCH Verlag GmbH amp Co KGaA 2002

[2] T Welton ldquoRoom-temperature ionic liquids Solvents for syn-thesis and catalysisrdquo Chemical Reviews vol 99 no 8 pp 2071ndash2083 1999


[3] F Endres ldquoIonic liquids solvents for the electrodeposition ofmetals and semiconductorsrdquo ChemPhysChem vol 3 no 2 pp144ndash154 2002

[4] K Murase K Nitta T Hirato and Y Awakura ldquoElectroche-mical behaviour of copper in trimethyl-n-hexylammonium bis((trifluoromethyl)sulfonyl)amide an ammonium imide-typeroom temperature molten saltrdquo Journal of Applied Electrochem-istry vol 31 no 10 pp 1089ndash1094 2001

[5] P-Y Chen and I-W Sun ldquoElectrochemical study of copper ina basic 1-ethyl-3-methylimidazolium tetrafluoroborate roomtemperature molten saltrdquo Electrochimica Acta vol 45 no 3 pp441ndash450 1999

[6] F Endres andA Schweizer ldquoThe electrodeposition of copper onAu(111) and on HOPG from the 6634 mol aluminium chlo-ride1-butyl-3-methylimidazolium chloride room temperaturemolten salt an EC-STM studyrdquo Physical Chemistry ChemicalPhysics vol 2 no 23 pp 5455ndash5462 2000

[7] W R Pitner and C L Hussey ldquoElectrodeposition of zinc fromthe Lewis acidic aluminum chloride-1-methyl-3-ethylimid-azolium chloride room temperature molten saltrdquo Journal of theElectrochemical Society vol 144 no 9 pp 3095ndash3103 1997

[8] P-Y Chen and I-W Sun ldquoElectrodeposition of cobalt and zinc-cobalt alloys from a lewis acidic zinc chloride-l-ethyl-3-methyl-imidazolium chloride molten saltrdquo Electrochimica Acta vol 46no 8 pp 1169ndash1177 2001

[9] Y Katayama S Dan T Miura and T Kishi ldquoElectrochemicalbehavior of silver in 1-ethyl-3-methylimidazolium tetrafluorob-oratemolten saltrdquo Journal of the Electrochemical Society vol 148no 2 pp C102ndashC105 2001

[10] Q Liao W R Pitner G Stewart C L Hussey and G R Staff-ord ldquoElectrodeposition of aluminum from the aluminum chlo-ride-1-methyl-3-ethylimidazolium chloride room temperaturemolten salt + benzenerdquo Journal of the Electrochemical Societyvol 144 no 3 pp 936ndash943 1997

[11] G E Gray P A Kohl and J Winnick ldquoStability of sodium elec-trodeposited from a room temperature chloroaluminatemoltensaltrdquo Journal of the Electrochemical Society vol 142 no 11 pp3636ndash3642 1995

[12] G Z Chen D J Fray and TW Farthing ldquoDirect electrochemi-cal reduction of titanium dioxide to titanium inmolten calciumchloriderdquo Nature vol 407 no 6802 pp 361ndash364 2000

[13] X Jin PGaoDWang XHu andG Z Chen ldquoElectrochemicalpreparation of silicon and its alloys from solid oxides in moltencalcium chloriderdquo Angewandte Chemie International Editionvol 43 no 6 pp 733ndash736 2004

[14] W-K Han J-W Choi G-H Hwang S-J Hong J-S Leeand S-G Kang ldquoFabrication of Cu nano particles by directelectrochemical reduction from CuO nano particlesrdquo AppliedSurface Science vol 252 no 8 pp 2832ndash2838 2006

[15] M-J Deng I-W Sun P-Y Chen J-K Chang and W-T TsaildquoElectrodeposition behavior of nickel in the water- and air-stable 1-ethyl-3-methylimidazolium-dicyanamide room-temp-erature ionic liquidrdquo Electrochimica Acta vol 53 no 19 pp5812ndash5818 2008

[16] A Metlen and R D Rogers ldquoThe second evolution of ionic liq-uids from solvents and separations to advanced materialsmdashenergetic examples from the ionic liquid cookbookrdquo Accountsof Chemical Research vol 40 pp 1182ndash1192 2007

[17] S Zhang X Qi X Ma L Lu and Y Deng ldquoHydroxyl ionicliquids the differentiating effect of hydroxyl on polarity due toionic hydrogen bonds between hydroxyl and anionsrdquo Journal ofPhysical Chemistry B vol 114 no 11 pp 3912ndash3920 2010

[18] X Wei L Yu X Jin D Wang and G Z Chen ldquoSolar-therm-ochromism of pseudocrystalline nanodroplets of ionic liquid-NiII complexes immobilized inside translucent microporousPVDF filmsrdquo Advanced Materials vol 21 no 7 pp 776ndash7802009

[19] H Sun L Yu X Jin X Hu D Wang and G Z Chen ldquoUnus-ual anodic behaviour of chloride ion in 1-butyl-3-methyli-midazolium hexafluorophosphaterdquo Electrochemistry Communi-cations vol 7 no 7 pp 685ndash691 2005

[20] J GHuddleston A E VisserWM Reichert H DWillauer GA Broker and R D Rogers ldquoCharacterization and comparisonof hydrophilic and hydrophobic room temperature ionic liquidsincorporating the imidazolium cationrdquo Green Chemistry vol 3no 4 pp 156ndash164 2001

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Nano

materials


Journal ofNanomaterials


reduced to metallic copper CuCu+ redox demonstrated aquasireversible charge transfer process

Endres and Schweizer [6] studied the electrodepositionof copper on Au (111) as the matrix at different temperaturesin trifluoromethanesulfonate imide 1-butyl-1-methylpyridine(BMPy-Tf

2N) ionic liquid and sediment layers was observed

using a scanning tunneling electronmicroscopy Experimen-tal results showed that the majority of the copper compoundin ionic liquids has low solubility the anodic dissolutioncould increase copper ions in the solution Study found thatthe curve showed a consistent feature andwith the increase oftemperature and current of copper the deposition potentialbecomes more positive

Although there a large number of electrodepositionbehavior of ionic liquids was reported in the literature [7ndash11] while most of them were still in the laboratory stagethe practical application of electrodeposition still has someproblems such as AlCl

3ionic liquid which can easily react

with moisture in the air and should be operated in the glovebox ionic liquid is constituted of dialkyl imidazolium cationand BF

4

minus PF6

minus although the stability is improved the costwas high and could be corrosive when placed it for a longtime In addition the low solubility of the metal salts in ionicliquids also limits the practical application

Following the successful electrochemical reduction ofsolid metal oxides to the metals in high temperature moltensalts [12ndash14] solid CuO nanoparticles were electroreduced tocopper nanoparticles in an aqueous electrolyte aiming forcatalytic applications [14]

In order to solve the problem of low solubility [Bmim]Cl can be added to [Bmim] PF

6 which can significantly

increase the solubility ofmetal chlorides themethod could becommonly used in electrochemical reduction of metal frommetal chlorides

Ionic liquids usually contain functional groups and couldbe divided into functional ionic liquids and conventionalionic liquids Function ionic liquid (task-specific ionic liquidabbreviated as TSIL) has a specific group introduced intothe structure which was provided with a unique functionFor example cuprous chloride and cupric chloride wererecently reported having a good solubility in 1-ethyl-3-methylimidazolium dicyanamide ionic liquid which may bedue to the complexation of dicyandiamide anion At thesame time electrochemical behavior of nickel chloride wasalso studied in such ionic liquid [15] The emergence offunctionalized ionic liquids enriches the types of ionic liquidsand leads the direction of the development of ionic liquids[16] Functionalized ionic liquids (FILs) containing alcoholon the alkyl arms have receivedmuch attention in the fields oforganic synthesis and catalysis Compared to traditional ILsthey show additional advantages such as alterable polaritylower viscosity and higher solubility for inorganic salts[17 18] Since the OH group has the positive effect onthe solubility this idea can extend to the correspondinghydroxyl-functionalized ionic liquids (HFILs) directly for theincreasing solubility of CuCl

2without using other additives

The solubility of transition metal halides can be increased byusing cations that are capable of forming complex ions withtransition metals In view of the good donor ligand property

that is known for the hydroxyl group transition metalcompounds should be soluble in the hydroxyl-functionalizedionic liquids (HFILs) and the preparation of a bath solutionfor electrodeposition is possible

Although HFILs may be potentially useful electrolytesexamples using these RTILs for metal electrodeposition arevery limited In order to evaluate the utility of this new RTILsystem the electrochemistry and electrodeposition of copperin theHFILs were studied in this workThe voltammetric andnucleation behavior of copper electrodeposition at Pt and Nielectrodes respectively were studied (see Figure 5)Hydroxylfunctional group and transition metal ions complexationincreased the solubility resulting in a larger depositioncurrent density and surface electrochemical reduction ofnanocopper particles deposited on metal Ni And redoxbehavior of copper ions of CuCl

2in hydroxyl ionic liquid

was different from the reported two single-electron redoxbehavior three oxidation peaks was found in our experimentand the cause of the third oxidation peak were also analyzedElectrodeposits of copper were prepared using controlledpotential electrolysis at copper substrates and examined byscanning electron microscopy (SEM)

2 Experimental

21 Instruments and Reagents The preparation and charac-terisation of 1-butyl-3-metylimidizolium chloride ([BMIM]Cl viscous liquid) and hexafluorophosphate ([BMIM] PF

6

liquid) followed the literature description [19 20] The pow-ders of cuprous chloride (CuCl gt97) and CuCl

2(99

Acros Organics) were thermally dried in vacuum beforeuse The solubility of these dried salts in [BMIM] PF

6was

measured as followsThe IL was first saturated with an excessamount of the salt at 80∘C under stirring for 48 h Afterstanding still for over 24 h the clear solution was sampledat different temperatures (80∘C 60∘C 40∘C and 28∘C) Thesample was treated with concentrated H

2SO4and H

2O2

and then diluted in double-distilled water before analysisby atomic absorption spectrometer (AAnalyst800 PerkinElmer)

Electrochemical workstation Shanghai CH InstrumentCompany Chi 660A Superheated tank Shanghai Exper-imental Instrument Factory ZKF030 Working electrode100 120583m Pt plate 07mm Cu plate 2mm times 5mmNi tabletsauxiliary electrode 6mm times 4mm Pt films 6mm times 3mmCutablets reference electrode AgAg+ electrode Electrolyzerlaminated glass structure adding ionic liquid volume ofapproximately 1mL with airway and seals

The electrolytic products from the IL were washed withacetonitrile twice dried in vacuum and analysed directlyby X-ray diffraction spectroscopy (XRD SHIMADZU X-ray6000 with Cu-K120572) and scanning electron microscopy (SEMHITACHIx-650)

22 Making Reference Electrode AgPF6was dissolved in

BMIMPF6 allowing the theoretical content of Ag+ to be

30Mm a silver lining will be inserted into the solution andseparated with the outer layer ionic liquid BMIMPF6 salt


0 1 2 3

05

00

minus05

minus10

minus15

minus20

minus2 minus1

Curr

ent d

ensit

y (m

A cm

minus2)

















0

1

2

3

4

5

minus1

minus2

minus3

First cycle

Second cycle

BackgroundCurr

ent d

ensit

y (m

A cm

minus2)



3OHmimBF





6 no Cu+ or Clminus





4CuCl

2









2in C3OHmimBF

4



0

1

2

3

4

5

minus1

minus2

minus3

Curr

ent d

ensit

y (m

A cm

minus2)


a1

a2

a3

c1

c2



3OHmimBF



10

0

minus10

minus20

minus30

minus40


a2a3

c2

c3

Curr

ent d

ensit

y (m

A cm

minus2)

Firstcycle



3OHmimBF







Curr

ent d

ensit

y (m

A cm

minus2)


45403530252015100500


40∘C80∘CBlank



2powder in the

C3OHmimBF



(C3OHmim-BF

4


3OHmim-

BF4


4




in theC3OHMIMBF




2C3OHMIMBF



3OHmimBF




(a)

1120583m

(b)

(c)

500nm

(d)


3OHmimBF

4Cl at



4 Summary











Acknowledgments


References





























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 1 2 3

05

00

minus05

minus10

minus15

minus20

minus2 minus1

Curr

ent d

ensit

y (m

A cm

minus2)

















0

1

2

3

4

5

minus1

minus2

minus3

First cycle

Second cycle

BackgroundCurr

ent d

ensit

y (m

A cm

minus2)



3OHmimBF





6 no Cu+ or Clminus





4CuCl

2









2in C3OHmimBF

4



0

1

2

3

4

5

minus1

minus2

minus3

Curr

ent d

ensit

y (m

A cm

minus2)


a1

a2

a3

c1

c2



3OHmimBF



10

0

minus10

minus20

minus30

minus40


a2a3

c2

c3

Curr

ent d

ensit

y (m

A cm

minus2)

Firstcycle



3OHmimBF







Curr

ent d

ensit

y (m

A cm

minus2)


45403530252015100500


40∘C80∘CBlank



2powder in the

C3OHmimBF



(C3OHmim-BF

4


3OHmim-

BF4


4




in theC3OHMIMBF




2C3OHMIMBF



3OHmimBF




(a)

1120583m

(b)

(c)

500nm

(d)


3OHmimBF

4Cl at



4 Summary











Acknowledgments


References





























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

1

2

3

4

5

minus1

minus2

minus3

Curr

ent d

ensit

y (m

A cm

minus2)


a1

a2

a3

c1

c2



3OHmimBF



10

0

minus10

minus20

minus30

minus40


a2a3

c2

c3

Curr

ent d

ensit

y (m

A cm

minus2)

Firstcycle



3OHmimBF







Curr

ent d

ensit

y (m

A cm

minus2)


45403530252015100500


40∘C80∘CBlank



2powder in the

C3OHmimBF



(C3OHmim-BF

4


3OHmim-

BF4


4




in theC3OHMIMBF




2C3OHMIMBF



3OHmimBF




(a)

1120583m

(b)

(c)

500nm

(d)


3OHmimBF

4Cl at



4 Summary











Acknowledgments


References





























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a)

1120583m

(b)

(c)

500nm

(d)


3OHmimBF

4Cl at



4 Summary











Acknowledgments


References





























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



research article electroreduction of copper dichloride powder to copper...

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