Electronic Supplementary Information

Hollow Micro-spherical Bismuth Oxy-chloride for Superior Visible Light Induced Dye-sensitized Photocatalytic Activity and its Theoretical Insight

Ratna Sarkara, Dimitra Dasb, Bikram Kumar Dasa, Anuradha Mitraa, Nirmalya S. Dasb, Subrata Sarkara and Kalyan K. Chattopadhyaya,b*

aDepartment of Physics, Jadavpur University, Kolkata 700032, IndiabSchool of Materials Science and Nanotechnology, Jadavpur University, Kolkata 700032, India

Section Name Title Page No.

ES1 Characterizations 2

ES2 Texture Coefficient analysis from XRD 4

ES3 FESEM and EDS Analysis 5

ES4 Raman and BET Analysis 8

ES5 Mott-Schottky Analysis 9

ES6 Photocatalysis Study 10

ES7 Zeta Potential and UV-Vis analysis of dye adsorbed catalyst

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ES8 Photocatalysis Study of Different Textile Dyes 12

ES9 Photocatalysis Reaction Mechanism 13

Table S1 Quantitative results as obtained from EDS analysis 14

Table S2 Rate constant values of time and temperature varied samples.

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Table S3 Rate constant values of B0h/B80 sample at different pH conditions

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Table S4 Rate constant values of B0h/B80 under visible and UV light irradiation

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Table S5 Rate constant values of degradation of B0h/B80 catalyst of different dyes in presence of visible light

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Table S6 Comparison of photocatalytic activity of different reported pure BiOCl catalysts

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Section ES1: Characterizations

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The as synthesized samples were analysed by employing several characterization techniques.

X-ray diffractometer (Rigaku Miniflex 600) with wavelength λ = 1.54056 Å for Cu Kα

source of radiation was used at a scan rate (2Ѳ) of 2 °min -1 at 40 kV and 40 mA to study the

phase formation of the powder samples. The chemical structure of the powder samples were

analysed by X-ray Photoelectron Spectroscopy (XPS) using a monochromatic Al KX-ray

source (h =1486.6 eV) and a hemispherical analyzer (SPECS HSA 3500). The morphology

of the samples was revealed from Field emission scanning electron microscopic study

(FESEM, Hitachi S-4800) which was equipped with an Energy Dispersive X-ray Spectra

(EDS) spectral analyser for analysing the elemental ratios of the samples and also from the

High Resolution Transmission Electron Microscopic study (HRTEM, JEOL-JEM 2100). For

FESEM measurement, powder samples were mounted on a carbon tape whereas for TEM

analysis, aqueous dispersions of the samples were drop-casted on carbon coated copper grid

(300 meshes). Fourier transform infrared spectroscopy (Shimadzu FTIR-8400S) revealed the

presence of various chemical bondings. Raman analysis of the powder samples was carried

out by Witec Raman spectrophotometer excited at 532 nm. UV-visible diffuse reflectance

spectra (DRS) of the powder samples were carried out by UV–Vis spectrophotometer

(Shimadzu UV-3600) using Barium Sulphate as a reflectance standard. Photoluminescence

spectroscopy (PL) of the samples were measured by JASCO FP 8300 spectrofluorometer

(150 Watt Xe lamp source; λex = 257.8 nm).

Photocatalytic activity measurements

Photocatalytic activity of the as‐synthesized BiOCl samples was measured at ambient

temperature at a pH of 7. In order to maintain the temperature of the catalytic reactor system

at a constant value, a double-walled glass beaker was used with continuous flow of cold

water in-between the two walls. To measure the photocatalytic activity of the as-prepared

BiOCl samples, 30 mg of the catalysts were dispersed in 40 mL of 10-5 mol/L RhB dye

solution. The catalyst dispersed solution was vigorously stirred for 1 hour under complete

dark condition to ensure proper adsorption-desorption equilibrium of the dye on the catalyst

surface. After this, the system was placed under a 400 W high pressure mercury lamp

(Phillips-HPL-N G/74/2, MBF-400W, 200-250V) covering the complete range from 365 nm

to 679 nm which was used as a visible-light source. A UV cut off filter (λ > 400 nm) was

employed to negate the UV emission. Similarly for the UV light source, two 40 W UV tubes

(Phillips) with an emission wavelength of 254.6 nm (UVC) was used. 3 mL of the reaction

solution was withdrawn from the suspension at regular time intervals which was immediately

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centrifuged to remove the catalyst; and the concentration of the RhB dye was monitored by

using an UV−Vis absorption spectrophotometer.

Scheme S1: Pictorial representation of the photocatalytic set-up in the laboratory employing

visible-light source.

Electrochemical Measurement

The Nyquist and the Mott-Schottky plots were analysed by Electro-chemical impedance

measurement performed by PGSTAT302N AUTOLAB in a three electrodes system. Prior to

the measurement, Ni foam of 1 cm X 1 cm was properly cleaned with diluted HCl solution

followed by a mixture of ethanol. The working electrode was prepared by mixing 40 mg of

the as synthesized BiOCl samples with 5 mg PVDF and 5 mg carbon black along with drop-

wise addition of a small amount of NMP solution to prepare black coloured slurry which was

stirred for 4 hours. The slurry was then uniformly applied on the clean Ni foam to prepare the

electrode for measurement. The Pt electrode was used as the counter electrode whereas the

reference electrode was typical calomel electrode (Ag/AgCl). 0.2 M Na2SO4 was used as the

electrolyte solution. The Nyquist measurements were taken at a stable frequency of 100000

Hz whereas the Mott-Schottky measurements were carried out at two frequencies of 2000 Hz

and 2500 Hz.

Section ES2: Texture Coefficient Analysis from XRD

3

Fig. S1. Texture coefficients along different lattice planes of (a) time and (b) temperature

varied BiOCl samples.

The texture coefficients of all the time and temperature varied BiOCl samples for 9 lattice

planes have been calculated from XRD data following the equation (1):

TC hkl=

I(hkl)/ I 0(hkl)

1n∑i=1

n

I(hkl)/ I 0(hkl)

…………….(1)

Where,

TC = is the texture coefficient for (hkl) plane,

I(hkl) = is the intensity of the (hkl) planes as calculated from the XRD data of BiOCl samples,

I0(hkl) = is the standard intensity of the (hkl) planes as taken from the JCPDS data and

‘n’ = is the number of XRD peaks taken into consideration during the calculation of TC.

It is evident from the bar graphs that the B0h/B80 sample shows the maximum value of

texture coefficient (1.75) along the (110) lattice plane. It is known that the deviation of

texture coefficient from unity indicates the preferential growth of the plane in that particular

direction [1]. Thus the maximum value of TC along the (110) direction for the B0h/B80

sample suggests the dominant orientation along that particular plane as compared to the other

time and temperature varied samples.

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Section ES3: FESEM and EDS Analysis

Fig. S2. FESEM images of (a & b) B1h, (c & d) B3h, (e & f) B6h and (g & h) B18h time

varied BiOCl samples.

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Fig. S3. FESEM images of (a & b) B40, (c & d) B60, (e & f) B100 and (g & h) B120

temperature BiOCl samples.

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100 nm

Fig. S4. (a) EDS pattern of B0h/B80, (b), (c) and (d) elemental mapping of Bi, O and Cl

materials.

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Section ES4: Raman and BET Analysis

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Fig. S5. Raman spectra of (a) time varied and (b) temperature varied samples; (c) Nitrogen

adsorption-desorption isotherms and (d) Pore size distributions of B0h/B80.

Section ES5: Mott-Schottky Analysis

Fig. S6. (a-h) Mott-Schottky plots of time and temperature varied BiOCl samples.

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Section ES6: Photocatalysis Study

Fig. S7. (a-i) Absorbance spectra of RhB dye in presence of as synthesized BiOCl catalysts;

(j) CT/C0 plot of B0h/B80 sample showing adsorption under dark stirring and subsequent

degradation after visible-light irradiation; (inset j) change in intensity of RhB dye solution in

presence of B0h/B80 during 100 min of dark stirring; (k) RhB dye adsorption and subsequent

desorption after heating up to 3 hours at 60 °C.

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(k)(j)

Section ES7: Zeta Potential and UV-Vis analysis of dye adsorbed catalyst

Fig. S8.(A) Zeta potential plot of B0h/B80 sample.

Fig. S8.(B) (a) Diffuse reflectance spectra and (b) UV-Vis Absorbance spectra of B0h/B80

powder sample in pure form, with RhB dye adsorbed after one hour dark stirring, and after 6

min of visible light irradiation.

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0

50000

100000

150000

-140 -120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120

Tota

l Cou

nts

Zeta Potential (mV)

Zeta Potential Distribution

Record 3: Cupr Sulph 1

Section ES8: Photocatalysis Study of Different Textile Dyes

Fig. S9. Visible-light assisted degradation of (a) MO dye, (b) Eosin B dye, (c) Mixed RhB

and Eosin B dyes, (d) Mixed RhB and MO dyes, (e) Mixed MO and Eosin B dyes and (f)

Mixture of RhB, MO and Eosin B dyes by B0h/B80 catalyst.

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Section ES9: Photocatalysis Reaction Mechanism

Scheme S2 (b). UV-light assisted degradation of RhB dye by hollow micro-spherical BiOCl

catalyst with exposed (1 1 0) crystal facet.

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Scheme S2 (a). Degradation of RhB dye by hollow micro-spherical morphology of

BiOCl catalyst with exposed (1 1 0) crystal facet.

Tables:

Table S1: Quantitative results as obtained from EDS analysis.

Materials Quantitative Result Bi O ClB40 Weight % 84.58 3.26 12.16

Atom % 42.54 21.40 36.06B60 Weight % 78.51 7.53 13.96

Atom % 30.29 37.97 31.75B100 Weight % 81.88 4.30 13.81

Atom % 37.31 25.60 37.09B0h/B80 Weight % 80.46 6.09 13.45

Atom % 33.62 33.24 33.14B1h Weight % 72.67 14.32 13.02

Atom % 21.60 55.59 22.81B3h Weight % 78.19 9.27 12.55

Atom % 28.62 44.31 27.07B6h Weight % 77.73 8.90 13.36

Atom % 28.49 42.63 28.88B18h Weight % 77.77 7.68 14.55

Atom % 29.48 38.03 32.50

Table S2: Rate constant values of time and temperature varied samples.

Samples name R2 values k values (min-1) Degradation efficiency %B0h/B80 0.8920 0.3423 98.92

B1h 0.9613 0.1286 95.41B3h 0.8866 0.1326 88.65B6h 0.7215 0.1494 94.95B18h 0.8688 0.2109 96.49B40 0.8304 0.3502 95.33B60 0.7046 0.2892 97.48B100 0.8689 0.1206 77.73B120 0.9398 0.0867 59.86

Table S3: Rate constant values of B0h/B80 sample at different pH conditions.

pH values R2 values k values (min-1) Degradation efficiency at 6 minpH = 1 0.6351 0.2903 99.95 %pH = 7 0.8920 0.3423 98.92 %

pH = 11.63 0.8445 0.0564 44.17 %

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Table S4: Rate constant values of B0h/B80 under visible and UV light irradiation.

Light variations R2 values k values(min-1)

Degradation efficiency at 6 min

Visible light 0.8920 0.3423 98.92 %UV-light 0.9764 0.1246 43.58 %

Table S5: Rate constant values of degradation of B0h/B80 catalyst of different dyes in presence of visible light.

Name of Dye R2 values k values (min-1)

Degradations efficiency

RhB dye 0.8920 0.3423 98.92 % (6 min)MO dye 0.9553 0.0502 96.40 % (40 min)

Eosin B dye 0.8466 0.0302 82.46 % (35 min)Mixed (RhB+MO) dye 0.7872 0.0855 96.80 % (18 min)

Mixed (RhB+EosinB) dye 0.9414 0.0280 99.51 % (100 min)Mixed (MO+EosinB) dye 0.9901 0.0154 97.87 % (210 min)

Mixed (RhB+MO+EosinB) dye 0.9933 0.0170 98.12 % (210 min)

Name of Catalyst

Dye degraded and Concentration of

Dye

Degradation Time (min)

Catalyst Dosage in 100 mL DI (g)

Source of Irradiation

krelative

(min-1)kabsolute =

krelative/Catalyst Dosage(min-1)

BiOCl [2] RhB (4.17 x 10-4 M) 120 0.1 Visible light

0.0670 0.6704

BiOCl [3] RhB (1.39 x 10-3 M) 120 0.067 Visible light

- -

BiOCl NS [4]

RhB (1.04 x 10-3 M) 20 0.05 Visible light

- -

BiOCl [5] RhB (4.17 x 10-4) 75 0.1 UV-light 0.0589 0.589BiOCl

HNS [6]RhB (10-5 M) 15 0.01 Visible

light- -

BiOCl [7] RhB (2.08 x 10-4 M) 32 0.02 UV-light 0.0255 1.275BiOCl [8] RhB (2.08 x 10-4 M) 60 0.5 Visible

light0.061 0.122

BiOCl [9] RhB (10-5 M) 4 0.1 Visible light

- -

BiOCl [10]

RhB (8.35 x 10-4 M) 110 0.06 Visible light

0.01574

0.2623

BiOCl [11]

RhB (10-6 M) 60 0.05 Visible light

0.112 2.24

BiOCl RhB (10-5 M) 20 0.02 Visible 0.272 13.6

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[12] lightBiOCl [This Work]

RhB (10-5 M) 6 0.075 Visible light

0.3423 4.564

Table S6: Comparison of photocatalytic activity of different reported pure BiOCl catalysts.

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