Water Oxidation with Visible Light Cobalt Selenide: A ...a BAS Epsilon Electrochemical System in a...
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Cobalt Selenide: A Versatile Cocatalysts for Photocatalytic Water Oxidation with Visible Light Guigang Zhang, Shaohong Zang, Zhi-An Lan, Caijin Huang*, Guosheng Li, and Xinchen Wang* Experimental Section All the chemicals were purchased without further purification. The purity of Co(AC) 2 ·3H 2 O, Na 2 SeO 3 , urea, ammonium tungstate, ammonium vanadium, and bismuth nitrate are 99 %. Synthesis of CoSe 2 : CoSe 2 was synthesized according to the literature with a few modifications. In a typical procedure, 1mmol (0.249 g) of Co(AC) 2 ·3H 2 O was added into 25 mL of DI water or 5 mL H 2 O/20 mL ethanol solution under magnetic stirring. About 10 min later, 5 mL of DETA (diethylenetriamine) and 1 mmol (0.173 g) of Na 2 SeO 3 were added. After further stirring for 0.5 h in a beaker to dissolve completely, the homogeneous solution was transferred into a 50mL Teflon-lined autoclave, which was sealed and maintained at 180 o C for 12 or 4 h and then naturally cooled to room temperature. The resulting solid product was collected and washed with DI water. Then, the nanocomposite powder was obtained by freeze-drying for next characterizations. Synthesis of g-C 3 N 4 : g-C 3 N 4 was obtained with a traditional polymerization fashion. Typically, 10 g urea was placed into a crucible with a cover. Then it was heated at 550 o C for 2 h with a heating rate of 5 o C/ min. The final pink yellow powder was obtained after cooled to room temperature. Synthesis of WO 3 and BiVO 4 : WO 3 was synthesized by direct anneal ammonium tungstate at 550 o C for 4 h. BiVO 4 was prepared by a homogenous precipitation according to a similar procedure reported previously. [19] Typically, urea (5 g) was dissolved in the mixed solution of ammonium vanadium and bismuth nitrate, then the solution was heated to 363 K with stirring. The urea hydrolysis led to an increase in the pH of the solution, resulting in the crystallization of BiVO 4 . After the crystalline BiVO 4 powder was formed, the slurry was continuously stirred at 363 K for 24 h. The product was filtered, washed, and dried. Synthesis of CoSe 2 Modified g-C 3 N 4 , WO 3 and BiVO 4 : In a typical process, a certain amounts of CoSe 2 (1, 2, 3, and 5 wt%) was added into a solution containing 0.1 g g-C 3 N 4 , WO 3 or BiVO 4 . The mixture was kept in ultrasonic bath for 10 min. The final products were obtained after drying with a vapour and dried in an oven at 80 o C for 10 hours. Synthesis of CoO x and CoS x Modified g-C 3 N 4 : CoO x and CoS x modified g-C 3 N 4 was prepared via a immersion strategy. In a typical process, a certain amounts of Co(AC) 2 ·3H 2 O and carbon nitride powders were mixed together in 5 mL of DI water. Then, after stirred for 5 min, the mixture was evaporated with a water vapour. The solids were then calcined in the air or H 2 S flow at 300 o C for 1 h. The final samples were collected after naturally cooled to room temperature. Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A. This journal is © The Royal Society of Chemistry 2015
Transcript of Water Oxidation with Visible Light Cobalt Selenide: A ...a BAS Epsilon Electrochemical System in a...
Cobalt Selenide: A Versatile Cocatalysts for Photocatalytic Water Oxidation with Visible Light
Guigang Zhang, Shaohong Zang, Zhi-An Lan, Caijin Huang*, Guosheng Li, and Xinchen Wang*
Experimental Section
All the chemicals were purchased without further purification. The purity of Co(AC)2·3H2O, Na2SeO3, urea, ammonium tungstate, ammonium vanadium, and bismuth nitrate are 99 %.
Synthesis of CoSe2: CoSe2 was synthesized according to the literature with a few modifications. In a typical procedure, 1mmol (0.249 g) of Co(AC)2·3H2O was added into 25 mL of DI water or 5 mL H2O/20 mL ethanol solution under magnetic stirring. About 10 min later, 5 mL of DETA (diethylenetriamine) and 1 mmol (0.173 g) of Na2SeO3 were added. After further stirring for 0.5 h in a beaker to dissolve completely, the homogeneous solution was transferred into a 50mL Teflon-lined autoclave, which was sealed and maintained at 180�oC for 12 or 4 h and then naturally cooled to room temperature. The resulting solid product was collected and washed with DI water. Then, the nanocomposite powder was obtained by freeze-drying for next characterizations.
Synthesis of g-C3N4: g-C3N4 was obtained with a traditional polymerization fashion. Typically, 10 g urea was placed into a crucible with a cover. Then it was heated at 550 oC for 2 h with a heating rate of 5 oC/ min. The final pink yellow powder was obtained after cooled to room temperature.
Synthesis of WO3 and BiVO4: WO3 was synthesized by direct anneal ammonium tungstate at 550 oC for 4 h. BiVO4 was prepared by a homogenous precipitation according to a similar procedure reported previously.[19] Typically, urea (5 g) was dissolved in the mixed solution of ammonium vanadium and bismuth nitrate, then the solution was heated to 363 K with stirring. The urea hydrolysis led to an increase in the pH of the solution, resulting in the crystallization of BiVO4. After the crystalline BiVO4 powder was formed, the slurry was continuously stirred at 363 K for 24 h. The product was filtered, washed, and dried.
Synthesis of CoSe2 Modified g-C3N4, WO3 and BiVO4: In a typical process, a certain amounts of CoSe2 (1, 2, 3, and 5 wt%) was added into a solution containing 0.1 g g-C3N4, WO3 or BiVO4. The mixture was kept in ultrasonic bath for 10 min. The final products were obtained after drying with a vapour and dried in an oven at 80 oC for 10 hours.
Synthesis of CoOx and CoSx Modified g-C3N4: CoOx and CoSx modified g-C3N4 was prepared via a immersion strategy. In a typical process, a certain amounts of Co(AC)2·3H2O and carbon nitride powders were mixed together in 5 mL of DI water. Then, after stirred for 5 min, the mixture was evaporated with a water vapour. The solids were then calcined in the air or H2S flow at 300 oC for 1 h. The final samples were collected after naturally cooled to room temperature.
Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A.This journal is © The Royal Society of Chemistry 2015
Characterization: XRD measurements were performed on a Bruker D8 Advance diffractometer with Cu Ka1 radiation. The UV/Vis spectra were recorded on a Varian Cary 500 Scan UV/Vis system. Electron paramagnetic resonance (EPR) measurements were carried out on a Bruker model A300 spectrometer. Themorphology of the sample was investigated by field emission scanning electron microscopy (SEM) (JSM-6700F). TEM was performed on a FEI Tencai 20 microscope. X-ray photoelectron spectroscopy (XPS) data were obtained on Thermo ESCALAB250 instrument with a monochromatized Al Kα line source (200 W). Photoluminescence spectra were recorded on an Edinburgh FI / FSTCSPC 920 spectrophotometer. Electrochemical measurements were conducted with a BAS Epsilon Electrochemical System in a conventional three electrode cell, using a Pt plate as the counter electrode and an Ag/AgCl electrode (3 M KCl) as the reference electrode.
Photocatalytic test for water oxidation: Photocatalytic O2 production was carried out in a Pyrex top-irradiation reaction vessel connected to a glass closed gas circulation system. For each reaction, 50 mg catalyst powder was well dispersed in an aqueous solution (100 mL) containing AgNO3 (0.01M) as an electron acceptor and La2O3 (0.2g) as a pH buffer agent. The reaction solution was evacuated several times to remove air completely prior to irradiation with a 300 W Xeon lamp with a working current of 15 A (Shenzhen ShengKang Technology Co., Ltd, China, LX300F). The wavelength of the incident light was controlled by applying some appropriate long-pass cut-off filters. The temperature of the reaction solution was maintained at room temperature by a flow of cooling water during the reaction. The evolved gases were analyzed in-situ by gas chromatography equipped with a thermal conductive detector (TCD) and a 5Å molecular sieve column, using Argon as the carrier gas.
Table S1. OER of CoSe2 modified g-C3N4 samples.
Solventa T / hb λ / nm Amount of cocatalyst / wt %
OER / μmol h-1
H2O 12 >300 3 19.2 H2O/ethanol 12 >300 3 27 H2O/ethanol 4 >300 3 34 H2O/ethanol 4 >420 3 9
a: the solvent used for the synthesis of CoSe2; b: hydrothermal treatment time.
64 62 60 58 56 54 52
I / a
.u.
BE / eV
Se 3d
3d5/2
54.7 eV
300 295 290 285
287.9 eV
I / a
.u.
BE / eV
C 1s
284.6 eV
410 408 406 404 402 400 398 396
403.9 eV401.2 eV
400.1 eV
I / a
.u.
BE / eV
N 1s 398.4 eV
Figure S1. High resolution XPS for Se 3d, C 1s, and N 2p of CoSe2 modified g-C3N4 samples.
Figure S2. SEM imagines of CoSe2 synthesized at different conditions.
0
10
20
30
40
5 wt
3 wt
2 wt
1 wt
0.5 wt
OER
/ m
ol h
-1
0 wt
Figure S3. OER of different amounts of CoSe2 modified g-C3N4 samples.
0 1 2 3 4 5 60
4
8
12
16
g-C3N4-Vis
g-C3N4-UV
Prod
uced
N2 /
m
ol
t / h
3wtCoSe2/g-C3N4-Vis3wtCoSe2/g-C3N4-UV
Figure S4. Time course of produced N2 for pure g-C3N4 and 3 wt CoSe2/g-C3N4 under visible and UV irradiation.
0 1 2 3 4 5 60
5
10
15
CoSe2/g-C3N4
g-C3N4
Prod
uced
O2 /
m
ol
t / h
Figure S5. Time course of produced O2 for pure g-C3N4 and 3 wt CoSe2/g-C3N4 under visible irradiation (λ> 420 nm).
0
10
20
30
40
6 th5 th4 th3 rd2 nd
OER
/ m
ol h
-1
Runs of reaction
1 st
Figure S6. OER of recycled 3 wt CoSe2/g-C3N4 under UV-Vis (λ> 300 nm).
200 300 400 500 600 700 800
Inte
nsity
/ a.
u.
/ nm
before after
10 20 30 40 50 60
I / a
.u.
2 / o
before
after
0.0 0.2 0.4 0.6 0.8 1.00
50
100
150
200
before after
V ads /
cm
3 .g-1
P / Po
Figure S7. DRS, XRD, BET, and TEM of 3 wt CoSe2/g-C3N4 before and after photocatalytic water oxidation.
Figure S8. TEM and EDS analysis of CoSe2/g-C3N4 before photocatalytic reaction.
Figure S9. TEM pictures of CoSe2/g-C3N4 after photocatalytic reaction.
c) d)
0
10
20
30
40 hybrid-150 oC
hybrid-80 oC
mixture
OER
/ m
ol h
-1
g-C3N4
Figure S10. OER of pure g-C3N4, g-C3N4 and CoSe2 mixture, CoSe2/g-C3N4 hybrid thermal treated at
80 and 150 oC.
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