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Z-scheme photocatalysis provides a promising solution to photocatalytic solar water splitting, yet restricted by inferior interfacial charge transfer. Here, we demonstrate a Z-scheme composite photocatalyst made of Fe 2 O 3 , a carbon layer, and g-C 3 N 4 that can achieve efficient hydrogen generation from solar water decomposition. The success relies on in-situ preparation of core-shell Fe 2 O 3 @C structure at the surface of g-C 3 N 4. Carbon as an intermediate layer thus acts as a bridge that significantly accelerates the migration of photogenerated electrons from Fe 2 O 3 conduction band to g-C 3 N 4 valence band. As a result, the highest rate of H 2 generation reaches 5.26 mmol h−1g−1. This activity is approximately 33-time greater than that achieved over pristine g-C 3 N 4 and about 4-time larger than that obtained over a Fe 2 O 3 /g-C 3 N 4 heterojunction without internal carbon layer. This work explicates the potential insight of the composite and paves a promising way to engineer the charge transfer behavior. [Display omitted] • A heterojunction made of Fe 2 O 3 , g-C 3 N 4 , and a carbon interlayer is obtained. • Photocatalytic water splitting proceeds via a Z-scheme mechanism over the catalyst. • The intermediate carbon layer acts as a channel for efficient electron transfer. • The photocatalytic activity for H 2 production is significantly improved. [ABSTRACT FROM AUTHOR]

The aggregate structures of photocatalyst particles are critical for their light absorption and scattering properties and thus significantly impact the photocatalytic performance toward solar hydrogen production. Herein, taking P25 TiO 2 nanoparticles as model photocatalysts, we calculate the optical properties of the aggregates of nanoparticles with the Discrete Dipole Approximation (DDA). A scattering phase function, which can reveal and predict the structural information of photocatalyst particles, is accordingly obtained. Specifically, it is found that the forward scattering is dominant when light is scattered on the particles, and this scattering mode becomes more intense with the increment of the particle size. Our results show that the scattering phase function is also in agreement with the Rayleigh-Gans-Debye (RGD) approximation. • Clusters of TiO 2 nanoparticles are established via fractal aggregation models. • Scattering properties are calculated via Discrete Dipole Approximation. • Forward-scattering dominates the phase function in modeling photocatalysis. • Phase functions agree with the prediction of Rayleigh-Gans-Debye approximation. [ABSTRACT FROM AUTHOR]

The feasibility of solar hydrogen production from water has long relied on the activity and stability of a given photocatalyst. In this study, using Cd x Zn 1-x S as a model photocatalyst, we demonstrated that the activity and stability of chalcogenide photocatalyst could be readily adjusted by changing the reaction conditions, including sacrificial reagents, reaction temperature. Our results showed that the combined use of proper sacrificial reagents play a key role against photocorrosion. Under optimized reaction conditions, the photocatalyst remained stable for more than 500 h. Under irradiation from a simulated sun light (light intensity: 789.92 W/m 2 ), the average rate of hydrogen evolution reached 1.43 mmol/h with an energy conversion efficiency from solar to hydrogen of 6.22%. [ABSTRACT FROM AUTHOR]

Abstract: A series of CdS and CdS/CNTs photocatalysts were successfully prepared by hydrothermal method and they were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), UV–visible optical absorption spectra (UV–Vis), etc. By studying their photocatalytic properties, it is found that, for CdS, photocatalysts prepared in appropriate alkaline environment presented higher hydrogen production activity, reaching 794.6 μmol h−1 g−1; the photocatalytic activity of CdS was obviously enhanced by combining it with CNTs via a special two-step hydrothermal method, and the corresponding hydrogen production rate reached 1.771 mmol h−1 g−1; the photocatalytic activity was further improved by loading co-catalyst NiS, achieving 12.13 mmol h−1 g−1. [Copyright &y& Elsevier]

Abstract: A series of Mn2+ doped CdS photocatalysts were prepared by a co-precipitation method and characterized by XRD, DRS, TEM, and XPS techniques. While the band gap, crystal phase and the morphology of CdS nanocrystal were not found to be affected noticeably by Mn2+ doping, there was an optimal Mn2+ doping content of wt 0.5% where the hydrogen production was more than doubled compared to pure CdS. Calculations of density functional theory (DFT) with plane waves and pseudopotentials were used to characterize the doping effect of Mn in cubic CdS. It is assumed that Mn2+ serving as shallow trapping sites can separate e−/h+ pairs at surface of nanosized CdS, so as to greatly reduce their surface recombination and which in turn leads to improved hydrogen yield. [Copyright &y& Elsevier]

Abstract: Decahedral Cu2WS4 was synthesized by a facile hydrothermal method and employed as photocatalyst for photocatalytic hydrogen production for the first time. The hydrothermal method avoids the traditional use of H2S for the preparation of such chalcogenide, which guarantees an environmental-friendly process. The properties of the Cu2WS4 samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Vis reflectance spectra, etc. The results showed that the decahedral Cu2WS4 possessed a band gap of ca. 2.1ev. The photocatalyst was demonstrated to be very active under visible light for hydrogen production. Especially, Cu2WS4 synthesized at 200 °C for 72 h showed the highest activity with the apparent quantum yield of 11% at 425 nm. The correlation between the preparation parameters and the photocatalytic properties were investigated. It was expected this first report of W-based chalcogenide photocatalyst would add to the photocatalyst group and lead to the finding of new photocatalyst with much higher activity. [ABSTRACT FROM AUTHOR]

Abstract: A novel catalyst-fixed way is present. And two series of novel CdS-incorporated special glass composite photocatalysts working under visible light were successfully prepared in this way by a two-step thermal sulfidation procedure for the use of catalyst-fixed system. One was by a high temperature way, and the other was by a low temperature way. The composite photocatalysts with different content of CdS prepared by the methods were found to show a good activity for the decomposition of water under visible light. The highest rate of H2 revolution is 1549μmol/(hgCdS) with wt1%-Pt loaded. The composites prepared by high and low temperature were characterized by X-ray diffraction (XRD), diffuse reflectance UV–vis spectra and scanning electron microscopy (SEM). The as-prepared photocatalysts exhibited different photochemical and photophysical properties for the combined way between glass-base and CdS. The photochemical and photophysical properties were very important in the catalyst-fixed system used for large-scale hydrogen production. [Copyright &y& Elsevier]

We report a photocatalytic system that utilizes Cd 0.5 Zn 0.5 S nanotwins decorated with various Ni-based co-catalysts for solar-driven hydrogen production through lignocellulose reformation. In this noble-metal-free system, Ni(OH) 2 emerges as the most effective Ni form in enhancing the photocatalytic evolution of H 2. By optimizing the composition with 3 wt% Ni(OH) 2 loading, we achieved the highest activity, with the hydrogen production rates of 7.00 mmol g−1 h−1 and 1.97 mmol g−1 h−1 from α-cellulose and waste straw photoreforming, respectively. This optimized composition exhibited the highest quantum efficiency of 7.68%. In principle, the lower potential of Ni2+/Ni compared to the conduction band of Cd 0.5 Zn 0.5 S facilitates the transfer of electrons from the conduction band of Cd 0.5 Zn 0.5 S to Ni(OH) 2. Specifically, during the photocatalytic reaction, a fraction of surface Ni(OH) 2 is reduced to Ni. The in-situ formed Ni clusters, along with the Ni(OH) 2 , enhance the separation photogenerated electrons and facilitate their transfer to H+, leading to significantly improved photocatalytic activity. This work not only provides an effective strategy for developing more efficient photocatalysts, but also offers a direct means of harnessing clean energy from abundant waste biomass on Earth. • Ni(OH) 2 /Ni atoms or clusters can serve as co-catalysts enhance the hydrogen production activity of Cd 0.5 Zn 0.5 S. • The cellulose/lignocellulose photoreforming system exhibits exceptional H 2 production efficiency. • The photothermal effect of the Ni(OH) 2 /Cd 0.5 Zn 0.5 S photocatalyst enhances the reaction activity. [ABSTRACT FROM AUTHOR]

Solar photocatalytic hydrogen production from water has been regarded as an ideal way addressing world energy and environmental crises. The technology has long relied on the development of an efficient photocatalyst. In addition to its photocatalytic performance, the large-scale production of certain photocatalyst from the viewpoint of particle application remains a challenge yet has received insufficient focus. Herein, we report an efficient and practical batch preparation system based upon hydrothermal method to the scalable production of chalcogenide nanoparticle photocatalyst. Taking the synthesis of Cd 0.5 Zn 0.5 S (CZS) twinned photocatalyst as an example, the outcome of CZS photocatalyst could reach ∼0.8 kg in this batched synthesis, which is about 390 times of the lab-scale production in mass amount. It was found that the twinned structure and visible-light absorption property were well maintained. Although further measurements toward the photocatalytic activity indicate slight decrement on solar H 2 generation compared to the lab-scale synthesized CZS photocatalyst, a high quantum efficiency of about 40.5% at 425 nm remained. The photocatalytic reaction could also stably proceed for 200 h without notable decay of H 2 -evolution rate. This work thus provides a powerful means for facile scaling up the chalcogenide nanoparticle photocatalyst at the kilogram level with both high quality and good reproducibility. [ABSTRACT FROM AUTHOR]

An ideal model composite made of CuS nanosheet (photothermal material) and g-C 3 N 4 was constructed through in-situ assembly procedure, along with integration of dual photochemical effect and photothermal effect. Consequently, optimized CN/CuS composite approaches remarkable photocatalytic performance improved by 44.5 times with regarding to that of pristine CN. This superiority can be assignable to inherent characteristic of CuS as photochemical component, with improved charge separation and enriched surface active-sites. Additionally, the critical contribution of photothermal effect in boosting water photosplitting was also experimentally validated. CuS nanosheet as hot spots enables rapid temperature increment around photocatalysts under visible/near-infrared (NIR) light irradiation. The heat converted from solar is conducive to increase carrier density, accelerate carrier mobility, alleviate onset potential and facilitate surface redox kinetics, so as to promote photocatalytic activity. It is believed that synergetic incorporation of photothermal and photochemical conversion could be expanded to other photocatalytic systems towards effective solar energy conversion. • CuS hot spot was integrated with g-C 3 N 4 in 2D-2D contact by in-situ assembly method. • CuS induced photothermal effect plays a critical role in boosting photocatalytic rate. • Photochemical/photothermal synergistic catalysis boosts H 2 evolution by 44.5 times. [ABSTRACT FROM AUTHOR]

Shape-controlled synthesis of semiconductor nanocrystals enables fine manipulation over their physicochemical properties. In this paper, unique Cd 0.9 Zn 0.1 S tetrapod nanostructures consisting of two different polymorphisms, i.e. , wurtzite and zinc blende, were successfully synthesized via a simple ethylenediamine-assisted solvothermal route. It is found that the temperature determines the formation of the zinc blende-structured seeds, while the ethylenediamine facilitates the subsequent preferential growth of the wurtzite phase arms. Furthermore, the tetrapods, characterized by a type-II staggered band alignment, have shown enhanced photocatalytic performance for H 2 generation from an aqueous solution containing electron donors under visible light irradiation, in comparison to the nanocrystals with distinct morphologies. Our results indicate that coupling different polymorphisms in a nanocrystal may be advantageous for photocatalytic proton reduction over single-crystal photocatalyst. [ABSTRACT FROM AUTHOR]

In this paper, a direct solar photocatalytic water splitting system with surface uniform concentrators (SUCs) is designed. Parameters influencing hydrogen production rates and energy conversion, viz. sacrificial agent concentration, catalyst concentration and circulation speed, are analyzed under typical days. It is found that the system with SUCs has better performances with higher sacrificial agent, higher catalyst concentration and lower speed: double and triple concentration of the sacrificial agent will improve the energy conversion efficiency by 4.52% and 19.35%, respectively; double and triple the photocatalyst concentration will improve the energy conversion efficiency by 81.32% and 200.00%, respectively; energy conversion efficiency under valve-half-closed and the valve-closed conditions are improve by 21.82% and 118.18% comparing with the valve-open condition. [ABSTRACT FROM AUTHOR]

Porous Cr 2 O 3 /g-C 3 N 4 composites were prepared by a facile one-pot pyrolysis method and showed enhanced visible-light-driven photocatalytic H 2 -evolution activities, with the highest rate 4.0 times of that for pure g-C 3 N 4 . During the one-pot process, accompanied by the pyrolysis of melamine to form g-C 3 N 4 , CrCl 3 ·6H 2 O acted as Cr precursor to form Cr 2 O 3 , and meanwhile functioned as pore-forming agent to increase the surface area and pore volume of g-C 3 N 4 . The cocatalytic effect of Cr 2 O 3 and the favorable textural properties of g-C 3 N 4 promoted the separation of photogenerated charge carriers, facilitated the diffusion, accumulation and adsorption of reactants, enriched the reactive sites for redox reaction, and thus resulted in the enhanced photocatalytic activities. This work presented an effective route to simultaneously optimize the compositions and micro/nano-structures of photocatalysts for H 2 evolution. [ABSTRACT FROM AUTHOR]