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Title: Effects of calcining temperature on photocatalysis of g-C{sub 3}N{sub 4}/TiO{sub 2} composites for hydrogen evolution from water

Abstract

Highlights: • TiO{sub 2} promotes melon to form at 400 °C, whereas it forms at 500 °C for only melamine. • The highest photocatalytic activity was achieved when calcination was performed at 400 °C. • Coordinated N−Ti−N bonds were formed in MA/TiO{sub 2} (400) and disappeared at high temperature. • The surface area decreased and the pore size increased with increasing of temperature. • Only MA/TiO{sub 2} (400) has a narrower band gap than pure g-C{sub 3}N{sub 4}. - Abstract: A composite of graphitic carbon nitride and TiO{sub 2} (g-C{sub 3}N{sub 4}/TiO{sub 2}) with enhanced photocatalytic hydrogen evolution capacity was achieved by calcining melamine and TiO{sub 2} sol-gel precursor. Characterization results reveal that heating temperature had a great influence on the structure, surface area and properties of the composites. Compared with the polycondensation of pure melamine, the presence of TiO{sub 2} precursor can promote the formation of melon at a low temperature. The highest photocatalytic activity of g-C{sub 3}N{sub 4}/TiO{sub 2}(400) was achieved when the calcination was performed at 400 °C, exhibiting H{sub 2} production rate of 76.25 μmol/h under UV–vis light irradiation (λ > 320 nm) and 35.44 μmol/h under visible light irradiation (λ > 420 nm). The highestmore » photocatalytic performance of g-C{sub 3}N{sub 4}/TiO{sub 2}(400) can be attributed to: (1) the strong UV–vis light absorption due to the narrow bandgap caused by synergic effect of TiO{sub 2} and g-C{sub 3}N{sub 4}, (2) high surface area and porosity, (3) the effective separation of photo-generated electron-holes owing to the favorable heterojunction between TiO{sub 2} and g-C{sub 3}N{sub 4}.« less

Authors:
; ; ; ; ;
Publication Date:
OSTI Identifier:
22581595
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 80; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CALCINATION; CARBON NITRIDES; COMPOSITE MATERIALS; ENERGY GAP; GRAPHITE; HETEROJUNCTIONS; HOLES; HYDROGEN; IRRADIATION; MELAMINE; PHOTOCATALYSIS; SEMICONDUCTOR MATERIALS; SOL-GEL PROCESS; SURFACE AREA; SURFACES; TEMPERATURE DEPENDENCE; TITANIUM OXIDES; VISIBLE RADIATION

Citation Formats

Qu, Ailan, E-mail: elainqal@163.com, Xu, Xinmei, Xie, Haolong, Zhang, Yangyu, Li, Yuyu, and Wang, Junxian. Effects of calcining temperature on photocatalysis of g-C{sub 3}N{sub 4}/TiO{sub 2} composites for hydrogen evolution from water. United States: N. p., 2016. Web. doi:10.1016/J.MATERRESBULL.2016.03.043.
Qu, Ailan, E-mail: elainqal@163.com, Xu, Xinmei, Xie, Haolong, Zhang, Yangyu, Li, Yuyu, & Wang, Junxian. Effects of calcining temperature on photocatalysis of g-C{sub 3}N{sub 4}/TiO{sub 2} composites for hydrogen evolution from water. United States. doi:10.1016/J.MATERRESBULL.2016.03.043.
Qu, Ailan, E-mail: elainqal@163.com, Xu, Xinmei, Xie, Haolong, Zhang, Yangyu, Li, Yuyu, and Wang, Junxian. Mon . "Effects of calcining temperature on photocatalysis of g-C{sub 3}N{sub 4}/TiO{sub 2} composites for hydrogen evolution from water". United States. doi:10.1016/J.MATERRESBULL.2016.03.043.
@article{osti_22581595,
title = {Effects of calcining temperature on photocatalysis of g-C{sub 3}N{sub 4}/TiO{sub 2} composites for hydrogen evolution from water},
author = {Qu, Ailan, E-mail: elainqal@163.com and Xu, Xinmei and Xie, Haolong and Zhang, Yangyu and Li, Yuyu and Wang, Junxian},
abstractNote = {Highlights: • TiO{sub 2} promotes melon to form at 400 °C, whereas it forms at 500 °C for only melamine. • The highest photocatalytic activity was achieved when calcination was performed at 400 °C. • Coordinated N−Ti−N bonds were formed in MA/TiO{sub 2} (400) and disappeared at high temperature. • The surface area decreased and the pore size increased with increasing of temperature. • Only MA/TiO{sub 2} (400) has a narrower band gap than pure g-C{sub 3}N{sub 4}. - Abstract: A composite of graphitic carbon nitride and TiO{sub 2} (g-C{sub 3}N{sub 4}/TiO{sub 2}) with enhanced photocatalytic hydrogen evolution capacity was achieved by calcining melamine and TiO{sub 2} sol-gel precursor. Characterization results reveal that heating temperature had a great influence on the structure, surface area and properties of the composites. Compared with the polycondensation of pure melamine, the presence of TiO{sub 2} precursor can promote the formation of melon at a low temperature. The highest photocatalytic activity of g-C{sub 3}N{sub 4}/TiO{sub 2}(400) was achieved when the calcination was performed at 400 °C, exhibiting H{sub 2} production rate of 76.25 μmol/h under UV–vis light irradiation (λ > 320 nm) and 35.44 μmol/h under visible light irradiation (λ > 420 nm). The highest photocatalytic performance of g-C{sub 3}N{sub 4}/TiO{sub 2}(400) can be attributed to: (1) the strong UV–vis light absorption due to the narrow bandgap caused by synergic effect of TiO{sub 2} and g-C{sub 3}N{sub 4}, (2) high surface area and porosity, (3) the effective separation of photo-generated electron-holes owing to the favorable heterojunction between TiO{sub 2} and g-C{sub 3}N{sub 4}.},
doi = {10.1016/J.MATERRESBULL.2016.03.043},
journal = {Materials Research Bulletin},
number = ,
volume = 80,
place = {United States},
year = {Mon Aug 15 00:00:00 EDT 2016},
month = {Mon Aug 15 00:00:00 EDT 2016}
}
  • Novel MoS{sub 2}/g-C{sub 3}N{sub 4} heterojunction photocatalysts were synthesized via a simple impregnation and heating methods. The products were characterized by X-ray diffraction, transmission electron microscopy and UV–vis diffuse reflectance spectra. The photocatalytic activities of MoS{sub 2}/g-C{sub 3}N{sub 4} samples were evaluated based on the hydrogen evolution experiments under visible light irradiation (λ > 400 nm). The UV–vis diffuse reflectance spectra revealed that the MoS{sub 2}/g-C{sub 3}N{sub 4} photocatalysts had strong absorption in the visible light region. The photocatalytic results indicated that the highest H{sub 2} evolution rate of 23.10 μmol·h{sup −1} was achieved on the 0.5 wt.% MoS{sub 2}–g-C{submore » 3}N{sub 4} sample, which was enhanced by 11.3 times compared to pure g-C{sub 3}N{sub 4}. This study may provide an approach to the development of novel heterojunction photocatalysts for hydrogen production under visible light irradiation. - Highlights: • MoS{sub 2}/g-C{sub 3}N{sub 4} photocatalyst is obtained by simple impregnation and heating methods. • and determined by XRD, TEM, UV-vis diffuse reflectance spectra. • the photocatalysts had strong absorption in the visible light region. • the highest H2 evolution rate was achieved on the 0.5wt% samples.« less
  • In this paper, a new g-C 3N 4/SrTa 2O 6 heterojunction photocatalyst was designed and prepared by chimie douce (soft chemistry) method where carbon nitride (g-C 3N 4) was deposited over the metastable perovskite phase of SrTa 2O 6. The morphological study of the heterojunction using SEM and STEM revealed that g-C 3N 4 nanofibers are dispersed uniformly on the surface of SrTa 2O 6 plates leading to the intimate contact between them. The heterojunction could achieve a high and stable visible light photocatalytic H 2 generation of 137 mmol/h/mole of g-C 3N 4, which is much larger than themore » amount of hydrogen generated by one mole of pristine g-C 3N 4. Finally, a plausible mechanism for the observed enhanced photocatalytic activity for the heterojunction is proposed on the basis of effective charge separation of photogenerated electron-hole pairs, supported by band position calculations and photo-physical properties of g-C 3N 4 and SrTa 2O 6.« less
  • ((n-C{sub 4}H{sub 9}){sub 4}N){sub 5}Na{sub 3}((1,5-COD)Ir{center dot}P{sub 2}W{sub 15}Nb{sub 3}O{sub 62}), 1, ((n-C{sub 4}H{sub 9}){sub 4}N){sub 5}Na{sub 3}((1,5-COD)Rh{center dot}P{sub 2}W{sub 15}Nb{sub 3}O{sub 62}), and ((n-C{sub 4}H{sub 9}){sub 4}N){sub 4.5}Na{sub 2.5}((C{sub 6}H{sub 6})Ru{center dot}P{sub 2}W{sub 15}Nb{sub 3}O{sub 62}) have been shown to catalyze the oxygenation of cyclohexene with molecular oxygen. The polyoxoanion-supported iridium (I) complex, 1, shows the highest activity of this group with a turnover frequency of 2.9 h{sup {minus}1} at 38{degree}C in CH{sub 2}Cl{sub 2} (540 total turnovers), which is 100-fold greater than its parent iridium compound, ((1,5-COD)IrCl){sub 2}. Additional experiments using H{sub 2}/O{sub 2} mixtures and H{sub 2}O{submore » 2} are also discussed. The apparent rate law for the oxidation of cyclohexene by O{sub 2} by 1 is -d(cyclohexene)/dt = k{sub 2} obsd {center dot} (1){sup 1}(cyclohexene){sup 1}P(O{sub 2}){sup 1{yields}0}. These compounds constitute the first examples of oxygenation catalysis using molecular oxygen and a polyoxoanion-supported transition-metal precatalyst.« less
  • A simple one-step calcination route was used to prepare Ti3+ self-doped TiO2/g-C3N4 heterojunctions by mixture of H2Ti3O7 and melamine. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR) spectroscopy, and UV-Vis diffuse reflectance spectroscopy (UV-vis DRS) technologies were used to characterize the structure, crystallinity, morphology, and chemical state of the as-prepared samples. The absorption of the prepared Ti3+ self-doped TiO2/g-C3N4 heterojunctions shifted to a longer wavelength region in comparison with pristine TiO2 and g-C3N4. The photocatalytic activities of the heterojunctions were studied by degrading methylene blue under a 30more » W visible-light-emitting diode irradiation source. The visible-light photocatalytic activities enhanced by the prepared Ti3+ self-doped TiO2/g-C3N4 heterojunctions were observed and proved to be better than that of pure TiO2 and g-C3N4. The photocatalysis mechanism was investigated and discussed. The intensive separation efficiency of photogenerated electron-hole in the prepared heterojunction was confirmed by photoluminescence (PL) spectra. The removal rate constant reached 0.038 min(-1) for the 22.3 wt % Ti3+ self-doped TiO2/g-C3N4 heterojunction, which was 26.76 and 7.6 times higher than that of pure TiO2 and g-C3N4, respectively. The established heterojunction between the interfaces of TiO2 nanoparticles and g-C3N4 nanosheets as well as introduced Ti3+ led to the rapid electron transfer rate and improved photoinduced electron-hole pair's separation efficiency, resulting in the improved photocatalytic performance of the Ti3+ self-doped TiO2/g-C3N4 heterojunctions.« less