Template-Induced High-Crystalline g-c 3 N 4 Nanosheets for. Enhanced Photocatalytic H 2 Evolution

Transcription

1 Template-Induced High-Crystalline g-c 3 N 4 Nanosheets for Enhanced Photocatalytic H 2 Evolution Weinan Xing, Wenguang Tu, Zhonghui Han, Yidong Hu, Qingqiang Meng, Gang Chen, * MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin , P.R. China. School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore , Singapore AUTHOR INFORMATION Corresponding Author * gchen@hit.edu.cn (G. C.) Experimental section The HC-CN photocatalyst was synthesized as follows: a certain amount of dicyandiamide were dissolved in distilled water under the stirring condition. Then the dispersion was poured into the alumina crucible and Ni foam was immersed in the dicyandiamide solution. The recrystallization of dicyandiamide anchored on the Ni-foam was obtained after the crucible transferred in an oven at 80 C for 12h. Subsequently, the crucible was put into the muffle furnace and heated at 550 C for 2 h with the rate of 2.5 C/min. Finally, the above product was immersed in 3 M HCl solution to remove nickel foam. After washed with distilled water several times, the HC-CN photocatalyst was got. For comparison, the CN photocatalyst was synthesized

2 under the same procedure without added the Ni foam. Characterization The crystal phase was analyzed via X-ray diffractometer (XRD, RigakuD/max-2000) equipped with a Cu-Kα radiation. The scanning angle range is with a scanning rate of 5 min -1. The morphologies and structures were observed from Transmission electron microscopy (TEM) and high-resolution TEM (HR-TEM), which carried out on FEI Tecnai G2 S-Twin. The Brunauer Emmett Teller (BET) surface areas were obtained from N 2 adsorption/desorption isotherms, measured by an AUTOSORB-1-MP surface analyzer at 77 K. The UV vis diffuse reflectance spectra (DRS) were measured via UV-vis diffuse reflectance spectra (DRS) a diffuse reflectance accessory. The Fluoro Max-4 Fluorescence spectrometer was used to obtain the photoluminescence (PL) spectra at room temperature. The electron paramagnetic resonance (EPR) measurements were tested on A300-10/12. The X-ray photoelectron spectroscopy (XPS) data was obtained on an American electronics physical HI5700ESCA system with X-ray photoelectron spectroscope using Al K ( ev) monochromatic X-ray radiation. The Fourier transform infrared (FT-IR) spectra were recorded on Therom IS 5/IR spectrometer (USA) and used KBr pellets. Photocatalytic and photoelectrochemical measurements The photocatalytic activities was determined by the photocatalytic H 2 evolution in a gas-tight circulation system with aside window. Typically, 0.1g photocatalyst was dispersed in the aqueous solution (270 ml deionized water and 30 ml triethanolamine solution as the sacrificial agent) Meanwhile, H 2 PtCl 6 6H 2 O (Pt, 3 wt %) was used as the co-catalyst. Before the reaction, the system was evacuated several times to remove air completely by purging with N 2. Visible light was provided by a 300 W Xenon lamp with cut off filter (λ > 400 nm). The amount of H 2 was analysis from the gas chromatography (Agilent 7890) with a thermal conductivity detector (TCD), and Ar was used as the carrier gas. The apparent quantum efficiency (AQE) was tested under the same experimental setup but with 420, 450, 500 and 550 nm band-pass filter. The

3 AQE was calculated as: AQE (%) = number of evolved H molecules 2 100/number of incident photons The photoelectrochemical measurement was carried out on CHI604C electrochemical working station with a standard three-electrode cell. The Pt pole as the counter-electrode, Ag/AgCl (in saturated KCl) as a reference electrode and the photocatalyst electrode coated at FTO glass electrode as the working electrode. The visible irradiation was obtained from 300 W Xe lamp (Trusttech PLS-SXE 300, Beijing) with cutoff filter (λ > 400 nm) M Na 2 SO 4 was used as the electrolyte solution. The working electrodes were prepared as follows: 25 mg ground photocatalyst was mixed with 300 µml terpilenol and maked a slurry. Subsequently, the slurry was injected onto the FTO glass electrode by the spin coater. At last, the electrolyte was dried at 80 C for 12 h. Figure S1. TEM (a) and HRTEM (b) of CN photocatalyst

4 Figure S2. EPR spectra of CN and HC-CN photocatalysts Figure S3. XRD pattern of Ni-foam-HC-CN Figure S4. TEM (a) and HRTEM (b) images of Ni-foam-HC-CN

5 Figure S5. FT-IR spectra of CN and HC-CN photocatalysts

6 Figure S6. XPS full spectra (a), High-resolution XPS spectra of (b) C1s, (c) N1s and (d) Ni 2p of CN and HC-CN photocatalysts.

7 Figure S7. Wavelength-dependent AQE of H 2 evolution over HC-CN photocatalyst Figure S8. TEM (a) and HRTEM (b,c) images of HC-CN photocatalyst after the potocatalytic reaction.

8 Figure S9. XPS valence band spectra of CN and HC-CN photocatalysts Figure S10. Schematic illustration of the band structure over CN and HC-CN photocatalysts Table S1 The contribution ratio of different peaks in N 1s for CN and HC-CN photocatalysts according to XPS analysis Sample C-N=C(sp 2 ) H-N-(C) 3 (sp 3 ) C-NH X charging ev ev ev ev CN 64.91% 21.11% 8.84% 5.14% HC-CN 70.00% 18.11% 8.28% 3.61%

9 Table S2 The decay life times and the average life time of photoexcited charge carriers in CN and HC-CN photocatalysts Sample Decay life times (ns) The average life time (ns) CN HC-CN Table S3 Comparison of photocatalytic H 2 evolution of photocatalyst from recent publications. Photocatalyst The amount Sacrificial The AQE(%) Ref. of Pt % agent wavelength HC-CN 3 TEOA 420 nm 6.17 This work g-c 3 N 4 mesoporous nanomesh 3 TEOA 420 nm P-g-C 3 N 4 Tubes 1 methanol 420 nm 5.68 CN-x 3 TEOA 420 nm CN KCl/ 0.1 g NH4Cl Carbon-Rich g-c3n4 2 TEOA 420 nm TEOA 400 nm Copolymer g-c 3 N 4 - TEOA 420 nm P-doped g-c 3 N 4 nanosheets 1 TEOA 420 nm HCN 3 TEOA 420 nm References (1) Han, Q.; Wang, B.; Gao, J.; Cheng, Z. H.; Zhao, Y.; Zhang, Z. P.; Qu, L. T. Atomically Thin Mesoporous Nanomesh of Graphitic C 3 N 4 for High-Efficiency

10 Photocatalytic Hydrogen Evolution. Acs Nano 2016, 10, (2) Guo, S. E.; Deng, Z. P.; Li, M. X.; Jiang, B. J.; Tian, C. G.; Pan, Q. J.; Fu, H. G. Phosphorus-Doped Carbon Nitride Tubes with a Layered Micro-nanostructure for Enhanced Visible-Light Photocatalytic Hydrogen Evolution. Angew Chem Int Edit 2016, 55, (3) Tu, W. G.; Xu, Y.; Wang, J. J.; Zhang, B. W.; Zhou, T. H.; Yin, S. M.; Wu, S. Y.; Li, C. M.; Huang, Y. Z.; Zhou, Y. et al. Investigating the Role of Tunable Nitrogen Vacancies in Graphitic Carbon Nitride Nanosheets for Efficient Visible-Light-Driven H-2 Evolution and CO2 Reduction. Acs Sustain Chem Eng 2017, 5, (4) Li, Y. X.; Xu, H.; Ouyang, S. X.; Lu, D.; Wang, X.; Wang, D. F.; Ye, J. H. In Situ Surface Alkalinized g-c 3 N 4 Toward Enhancement of Photocatalytic H 2 Evolution Under Visible-Light Irradiation. J Mater Chem A 2016, 4, (5) Li, Y. F.; Yang, M.; Xing, Y.; Liu, X. C.; Yang, Y.; Wang, X.; Song, S. Y. Preparation of Carbon-Rich g-c3n4 Nanosheets with Enhanced Visible Light Utilization for Efficient Photocatalytic Hydrogen Production. Small 2017, 13 (33), (6) Fan, X. Q.; Zhang, L. X.; Cheng, R. L.; Wang, M.; Li, M. L.; Zhou, Y. J.; Shi, J. L. Construction of Graphitic C 3 N 4 -Based Intramolecular Donor - Acceptor Conjugated Copolymers for Photocatalytic Hydrogen Evolution. Acs Catal 2015, 5, (7) Ran, J. R.; Ma, T. Y.; Gao, G. P.; Du, X. W.; Qiao, S. Z. Porous P-doped Graphitic Carbon Nitride Nanosheets for Synergistically Enhanced Visible-Light Photocatalytic H 2 Production. Energ Environ Sci 2015, 8, (8) Wang, X. L.; Fang, W. Q.; Liu, W. Q.; Jia, Y.; Jing, D. W.; Wang, Y.; Yang, L. Y.; Gong, X. Q.; Yao, Y. F.; Yang, H. G.; Yao, X. D. Bronsted Base Site Engineering of Graphitic Carbon Nitride for Enhanced Photocatalytic Activity. J Mater Chem A 2017, 5 (36),