reduction of co2 with visible light perovskite oxide lacoo ... · perovskite oxide lacoo3...
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Electronic Supplementary Information
Perovskite oxide LaCoO3 cocatalyst for efficient photocatalytic reduction of CO2 with visible light
Jiani Qin, Lihua Lin, Xinchen Wang*
State Key Laboratory of Photocatalysis on Energy and Environment, College of
Chemistry, Fuzhou University, Fuzhou 350002, People’s Republic of China
Email: [email protected]
Electronic Supplementary Material (ESI) for ChemComm.This journal is © The Royal Society of Chemistry 2018
Experimental section
Synthesis of coralline-like LaCoO3 material: In a typical synthesis, the equal molar
mass of Co(NO3)3·6H2O and La(NO3)3·6H2O were dissolved in a small amount of
deionized water with vigorous stirring, when the two were dissolved and mixed
completely, certain amount of citric acid was added as a complexing agent. The molar
ratio of the added citric acid and the total metal salts was 1:1. Then viscous gel was
obtained by heating the mixture solution at 80 ºC oil bath. Move the gel to a 100 ºC
electron oven and keeping several hours. The pink spongy material obtained was
crushed and calcined at 600 ºC for 6 hours on a muffle furnace with air atmosphere.
The final black powder was the target material LaCoO3.
Characterization: Powder X-ray diffraction (XRD) measurements were conducted on
a Bruker D8 Advance diffractometer with Cu Ka1 radiation. The morphologies and
energy dispersive X-ray (EDX) spectrum of the sample were obtained by a Hitachi New
Generation SU8010 field emission scanning electron microscope (FESEM).
Transmission electron microscopy (TEM) was performed on a JEOL model JEM 2010
EX instrument. The nitrogen adsorption–desorption and CO2 adsorption isotherms were
collected by a Micromeritics ASAP2020 equipment. A Thermo ESCALAB250
instrument with a monochromatized Al Ka line source (200 W) was employed for X-
ray photoelectron spectroscopy (XPS) measurements. UV–Vis diffuse reflectance
spectra (UV–Vis DRS) were performed on a Varian Cary 500 Scan UV-Vis
spectrophotometer with barium sulfate as the reference. Inductively coupled plasma
mass spectrometry (ICP-MS, X Series II Thermo Scientific) was employed to analyze
the supernatant of the reaction mixture. A BAS Epsilon Electrochemical System with a
conventional three electrode cell was used to measure the Mott-Schottky curves. A Pt
plate and an Ag/AgCl electrode were used as the counter electrode and the reference
electrode, respectively. The working electrode was prepared by dip-coating 20 μL
LaCoO3 catalyst slurry (3 mg mL-1 in water) on indium-tin oxide (ITO) glasses, and the
active area is confined to 0.25 cm2. After air-drying, the film electrodes were further
dried at 300 ℃ for 30 min to improve adhesion. A 0.2 M Na2SO4 aqueous solution was
chosen as the supporting electrolyte and was purged with nitrogen to remove O2 before
any measurements. For the Mott-Schottky experiment, the potential ranged from -0.4
to 0.1 V (vs. Ag/AgCl), and the frequency were controlled at 500, 1000, and 1500 Hz.
An Agilent 7820A gas chromatography equipped was used to analyze the produced
gases, which equipped with a thermal conductivity detector (TCD) and a TD-01 packed
column, and using high purity argon as the carrier gas. The products of the 13CO2
isotopic experiment were analyzed by HP 5973 GC-MS.
Photocatalytic performance: In the established photocatalytic CO2 reduction reaction
system, 300 W Xenon Lamp with a 420 nm cut-off filter was used for the light source,
a circulation condensate equipment was employed to control the reaction temperature
at 30 ºC. For the reaction, [Ru(bpy)3]Cl2·6H2O (8 mg) and LaCoO3 (1 mg) were
dispersed into a CO2-saturated MeCN/H2O/TEOA (3:2:1, v/v/v) mixture solution with
magnetic stirring in an airtight reactor. After the reaction, the produced gases were
analysed by a gas chromatography.
Table S1 Comparison of catalytic activity of perovskite LaCoO3 with spinel cobalt
oxides under similar reaction conditions.
Entry Cocatalyst CO / μmol H2 / μmol CO+H2 / μmol Ref.
1 LaCoO3 44.2 12.5 56.7 This work
2 NiCo2O4 21.0 4.0 25.0 [1]
3 MnCo2O4 27.0 8.0 35.0 [2]
4 ZnCo2O4 25.1 8.7 33.8 [3]
Reaction conditions: Ru(bpy)3Cl2·6H2O (8 mg), cocatalyst (1 mg), TEOA (1 ml), solvent (5 ml,
MeCN : H2O = 3: 2), λ≧420 nm, 30 ℃, 1 h.
[1] Z. Wang, M. Jiang, J. Qin, H. Zhou and Z. Ding, Phys. Chem. Chem. Phys., 2015, 17, 16040.
[2] S. Wang, Y. Hou and X. Wang, ACS Appl. Mater. Interfaces, 2015, 7, 4327.
[3] S. Wang, Z. Ding and X. Wang, Chem. Commun., 2015, 51, 1517.
Table S2 The effect of volume ratio of MeCN/H2O on CO2 photoreaction performance.
Entry VMeCN / VH2O CO / μmol H2 / μmol Sel.CO / %
1 5/0 4.1 6.7 38.0
2 4/1 31.2 19.5 61.5
3 3/2 28.5 9.1 75.8
4 2/3 13.7 2.8 83.0
5 1/4 2.2 0.1 95.7
6 0/5 0.6 0.04 93.8
Table S3 Comparison of CO2 photoreduction performance of similar reaction systems.
Catalyst Photosensitizer lightCO-evolving rate
/ μmol h-1 g-1Refs.
LaCoO3 [Ru(bpy)3]2+ 420 nm 44200 This work
Co3O4 [Ru(bpy)3]2+ 420 nm 3523 [4]
Ni-MOF [Ru(bpy)3]2+ 420 nm 15866 [5]
CoSn(OH)6 [Ru(bpy)3]2+ 400 nm 18700 [6]
[4] C. Gao, Q. Meng, K. Zhao, H. Yin, D. Wang, J. Guo, S. Zhao, L. Chang, M. He, Q. Li, H. Zhao, X. Huang, Y. Gao, and Z. Tang, Adv. Mater., 2016, 28, 6485.
[5] K. Niu, Y. Xu, H. Wang, R. Ye, H. Xin, F. Lin, C. Tian, Y. Lum, K. Bustillo, M. Doeff, M. Koper, J. Ager, Sci. Adv., 2017, 3, e1700921.
[6] X. Lin, Y. Gao, M. Jiang, Y. Zhang, Y. Hou, W. Dai, S. Wang, Z. Ding, Appl. Catal. B: Environ., 2018, 224, 1009.
Fig. S1 XPS spectra of the prepared coralline-like perovskite LaCoO3 material: (a) survey spectrum and the high-resolution spectra of (b) Co 2p, (c) La 3d and (d) O 1s.
Fig. S2 (a) N2 adsorption-desorption isotherms at 77K and (b) CO2 adsorption isotherm at 273K.
Fig. S3 GC-MS spectra of 13C-labelled isotropic experiment.
Fig. S4 XRD spectra (a) and XPS patterns (b and c) of the LaCoO3 sample before and after photocatalytic reactions.
Fig. S5 Mott-Schottky plots of the prepared LaCoO3 material.
0
5
10
15
20
25
30
35
8:316:1 8:1
Prod
uced
Gas
(m
ol)
mRu : mLaCoO3
CO H2
160:1
Fig. S6 Yields of CO and H2 as a function of the mass ratio of Ru/LaCoO3 in the CO2 reduction reaction system.
0 30 60 90 120 150 180
0
20
40
60
80
100
120
Prod
uced
Gas
(m
ol)
Time (min)
CO H2
fresh Ru
Fig. S7 Yields of CO and H2 as a function of reaction time.
The apparent quantum yield (AQY) was conducted under the same reaction conditions. The incident light was used a low-power 420 nm LED lamp. The AQY is calculated as following:
AQY (%) = 2(number of the produced molecule)/(number of photons) 100%
The calculation procedures of apparent quantum yield are in the following:
2H+ H2 2e- 1h 0.3 mol
CO2 CO 2e- 1h 1.4 mol
Major parameters:
Light intensity: I = 19.8 mWcm-2
P = ItS, (t = 3600s, S = 1 cm2)
E = nhv, (h = 6.626×10-34 js, = 420 nm)
So, AQY = 1.36 %.