A comparative study of semiconductor photocatalysts for hydrogen production by visible light using different sacrificial substrates in aqueous media (original) (raw)
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A CdS/TiO 2 nano-bulk composite photocatalyst consisting of bulky CdS with a high crystallinity decorated with nanosized TiO 2 particles was fabricated by precipitation method and sol-gel synthesis. This configuration of the composite photocatalyst exhibited a very high rate of hydrogen production under visible light irradiation (λ ≥ 420 nm) from water containing sulfide and sulfite as hole scavengers. In this work, we investigated the physicochemical properties of CdS(bulk)/TiO 2 composite photocatalysts and optimized their preparation conditions for the high photocatalytic activity of hydrogen production from water containing Na 2 S and Na 2 SO 3 as a sacrificial reagents under visible light irradiation.
Catalysts, 2019
Photocatalytic water splitting is a sustainable technology for the production of clean fuel in terms of hydrogen (H2). In the present study, hydrogen (H2) production efficiency of three promising photocatalysts (titania (TiO2-P25), graphitic carbon nitride (g-C3N4), and cadmium sulfide (CdS)) was evaluated in detail using various sacrificial agents. The effect of most commonly used sacrificial agents in the recent years, such as methanol, ethanol, isopropanol, ethylene glycol, glycerol, lactic acid, glucose, sodium sulfide, sodium sulfite, sodium sulfide/sodium sulfite mixture, and triethanolamine, were evaluated on TiO2-P25, g-C3N4, and CdS. H2 production experiments were carried out under simulated solar light irradiation in an immersion type photo-reactor. All the experiments were performed without any noble metal co-catalyst. Moreover, photolysis experiments were executed to study the H2 generation in the absence of a catalyst. The results were discussed specifically in terms of...
Hydrogen production from Hydrogen Sulfide Wastestream using Ru/Cd 0.6 Zn 0.4 S Photocatalyst
The depletion of non-renewable energy source and increasing levels of environmental pollution are both becoming serious global concerns. The conversion of solar energy into hydrogen via H S splitting process assisted by semiconductor photocatalysts is one of the most attractive and focused way of achieving clean and renewable energy systems. A novel Ru 2+ doped Cd 2 0.6 Zn S nanophotocatalyst was synthesized by co-precipitation method. The physical characterization of the nanophotocatalyst had been carried out by XRD, SEM, UV-DRS and EDS. The XRD patterns showed that a new structural peak was found instead of original peaks with mixture of Ru doped Cd 0.6 Z 0.4 0.4 S having a particle size of 4.9 nm. The band gap energy of 2.61 eV and threshold wavelength of 475 nm were found using UV-DRS.The photocatalytic generation of H from simulated sulfide wastewater under visible light irradiation were conducted with two different reactors viz., trapezoidal and cylindrical tapered bottom reactors. The comparison of performance also reveals that the trapezoidal reactor produce higher rate of H 2 production ( 4063 µmol/h ) than the cylindrical tapered bottom reactor (3169 µmol/h ). The quantum efficiency of 10.1% at 560 nm was found in trapezoidal reactor. This composite exhibited much higher 2 photocatalytic activity for the generation of hydrogen (H 2 ) .
International Journal of Hydrogen Energy, 2009
The kinetics of hydrogen production from photolysis of water on alumina supported Pt-CdS catalyst using visible light has been studied. An induction period with negligible rate was observed upon illumination of catalyst. The rate gradually increases and again falls down. The rate has been observed to be proportional to the sulfide ions adsorbed on the surface of CdS. The induction period has been related to the re-establishment of adsorption equilibrium of sulfide ions on the catalyst surface under illumination. The decrease in rate is due to the deactivation of catalyst by hydrogen. A power law type rate expression for hydrogen production has been proposed which takes into account the deactivation of the catalyst.
Water Science and Technology, 2015
An attractive and effective method for converting solar energy into clean and renewable hydrogen energy is photocatalytic water splitting over semiconductors. The study aimed at utilizing organic sacrificial agents in water, modeled by formic acid, in combination with visible light driven photocatalysts to produce hydrogen with high efficiencies. The photocatalytic hydrogen production of cadmium sulfide (CdS)/titanate nanotubes (TNTs) binary hybrid with specific CdS content was investigated. After visible light irradiation for 3 h, the hydrogen production rate of 25 wt% CdS/TNT achieved 179.35 μmol·h−1. Thanks to the two-step process, CdS/TNTs-WO3 ternary hybrid can better promote the efficiency of water splitting compared with CdS/TNTs binary hybrid. The hydrogen production of 25 wt% CdS/TNTs-WO3 achieved 212.68 μmol·h−1, under the same condition. Coating of platinum metal onto the WO3 could further promote the reaction. Results showed that 0.2 g 0.1 wt% Pt/WO3 + 0.2 g 25 wt% CdS/T...
New Journal of Chemistry, 2014
In this work, we have synthesized CdS quantum dots and also supported CdS nanoparticles on ZSM-5 type metalosilicates (ferrisilicate and aluminosilicate) as CdS-metalosilicate composites. The photocatalytic activity for hydrogen production over the prepared catalysts was investigated. It can be observed that the synthesis of CdS quantum dots by a solvothermal method results in the enhancement of photocatalytic activity of this semiconductor in comparison to other procedures, which has been reported previously. Our objective was to improve the photocatalytic activity of our synthesized CdS nanoparticles; for this purpose, we have supported CdS on metalosilicates and investigated their photocatalytic activity. These composites show high efficiency for hydrogen production under visible light irradiation. This suggests that, due to the high surface area of metalosilicates, the effective and homogenous dispersion of CdS particles on the external surface or within the pores of metalosilicate can be achieved by supporting the nano-particles which inhibits the agglomeration of the formed semiconductor. We have thus distinguished that supporting of CdS nanoparticles leads to improvement of the photocatalytic activity in water reduction; so that the hydrogen production rate for CdS-metalosilicate composite was about 11 mmol h À1 g cat À1 ; which is significantly higher than that of unsupported CdS nanoparticles.
Solar hydrogen photoproduction from sulphide/sulphite substrate
International Journal of Hydrogen Energy, 1992
The photoproduction of hydrogen from alkaline solutions of sulphide/sulphite is one of the photocatalytic processes which has been considered recently for a possible scaling-up. This process could be combined with, or be an alternative to, the current processes that profit from the sulphur coming from the desulphuration units ofoil refineries. Keeping the scaling-up in mind, some basic research and system analysis have been done. Different types of CdS-based semiconductor photocatalysts have been prepared, characterized and tested. A solar simulator device, with a cylinder-parabolic mirror and a tubular photoreactor, has been designed. Studies on the radiation field, fluid dynamics, catalyst stability and kinetic variables have been carried out. The maximum quantum yield obtained was 18%.
Effective Photocatalytic Hydrogen Evolution by Cascadal Carrier Transfer in the Reverse Direction
ACS omega, 2018
Visible-light-responsive photocatalysts used in the highly efficient hydrogen production exhibit several disadvantages such as photocorrosion and fast recombination. Because of the potential important applications of such catalysts, it is crucial that a simple, effective solution is developed. In this respect, in this study, we combined SiC (β modification) and TiO 2 with CdS to overcome the challenges of photocorrosion and fast recombination of CdS. Notably, we found that when irradiated with visible light, CdS was excited, and the excited electrons moved to the conduction band of TiO 2 , thereby increasing the efficiency of charge separation. In addition, by moving the holes generated on CdS to the valence band of SiC, in the opposite direction of TiO 2 , photocorrosion and fast recombination were prevented. As a result, in the sulfide solution, the CdS/SiC composite catalyst exhibited 4.3 times higher hydrogen generation ability than pure CdS. Moreover, this effect was enhanced with the addition of TiO 2 , giving 10.8 times higher hydrogen generation ability for the CdS/SiC/TiO 2 catalyst. Notably, the most efficient catalyst, which was obtained by depositing Pt as a cocatalyst, exhibited 1.09 mmol g −1 h −1 hydrogen generation ability and an apparent quantum yield of 24.8%. Because water reduction proceeded on the TiO 2 surface and oxidative sulfide decomposition proceeded on the SiC surface, the exposure of CdS to the solution was unnecessary, and X-ray photoelectron spectroscopy confirmed that photocorrosion was successfully suppressed. Thus, we believe that the effective composite photocatalyst construction method presented herein can also be applied to other visible-light-responsive powder photocatalysts having the same disadvantages as CdS, thereby improving the efficiency of such catalysts.