Well-defined FeP/CdS heterostructure construction with the assistance of amine for the efficient H2 evolution under visible light irradiation

The photocatalyst is a crucial factor in determining solar-to-H₂ efficiency for solar-driven water splitting. Here, the FeP/CdS well-defined heterostructure was elaborately designed and successfully constructed in-situ to achieve efficient water splitting by using a simple and green solvothermal approach. In the synthetic process, the ethylenediamine plays an important role in the construction of intimate contact interface between FeP and CdS. This good quality FeP/CdS heterostructure can efficiently promote charge separation and transportation, and therefore the charge recombination of CdS was significantly suppressed. As a result, the as-synthesized FeP/CdS heterostructure showed excellent photocatalytic performance under visible-light irradiation with an optimal hydrogen evolution rate of 37.92 mmol g⁻¹ h⁻¹ and an apparent quantum yield of 31.50% at 420 nm far exceeding that of pristine CdS by more than 122 folds. This rate, to the best of our knowledge, outperforms other similar catalytic systems.     

MoS2/CdS nanosheet-on-nanorod: An efficient photocatalyst for H2 generation from lactic acid decomposition

The CdS shows high selectivity on H₂ for photocatalytic lactic acid decomposition. However, the low efficiency caused by ultrafast charge recombination was not well addressed. Herein, MoS₂/CdS nanoheterostructure with intimate contact interface was synthesized in-situ and used as an efficient photocatalyst for H₂ generation. The optimum H₂ generation rate of MoS₂/CdS is 45.20 mmol g^?1 h^?1 which significantly boosts the activity of CdS (0.27 mmol g^?1 h^?1) by more than 167 folds. Band alignment of MoS₂ and CdS promoting charge transfer and separation contributes to the enhanced catalytic activity, which was well verified by multiple characterization approaches.     

Direct Z-Scheme NiWO4/CdS nanosheets-on-nanorods nanoheterostructure for efficient visible-light-driven H2 generation

Exploiting efficient catalysts is of interest for solar-driven water splitting. Herein, a novel NiWO₄/CdS nanosheets-on-nanorods direct Z-Scheme heterostructure was developed by using a facile in-situ approach. The optimized NiWO₄/CdS heterostructure shows a H₂ evolution rate of 26.43 mmol g^?1 h^?1 exceeding that of bare CdS by more than 75 folds. Systematic investigations reveal the nanostructures with numerous active sites, intimate contact interface, and enhanced charge separation rate synergistically account for the outstanding performance of the NiWO₄/CdS. Moreover, the band structures were detailedly analyzed and the tentative photocatalytic mechanism was proposed, which could contribute to deeply understanding the catalytic process and guide the synthesis of the efficient heterostructure. These findings and strategies may have great significance in promoting the development of highly efficient and low-cost photocatalysts.     

Heteroepitaxial growth of core-shell ZnO/CdS heterostructure for efficient and stable photocatalytic hydrogen generation

Solar-driven water splitting provides a promising way to generate clean and renewable hydrogen. The efficiency and stability are of importance for practical application of this technology. Herein, colloidal ZnO/CdS heterostructure catalysts were obtained via a two-step heteroepitaxial growth strategy. It was discovered that the anion exchange step plays an important role in construction of core-shell ZnO/CdS heterostructure and photo-induced electron-hole separation is promoted by reducing the charge carriers transfer distance in prepared ultra-small heterostructure. By optimizing the molar ratio of the ZnO and CdS components, the highest hydrogen generation rate of 669.6 μmol/h (100 mg) was achieved without any cocatalyst loading in the presence of S^2? and SO₃^2? as sacrificial reagents. Furthermore, the heterostructure displayed excellent photocatalytic stability for ～72 h. The photocatalytic performance of as-prepared nanoscale ZnO/CdS is superior than that of the well-studied bulk ZnO/CdS heterostructures, demonstrating its great potential in practical application of photocatalytic water splitting.     

Self-assembled CdS@BN core-shell photocatalysts for efficient visible-light-driven photocatalytic hydrogen evolution

CdS@BN NRs core-shell photocatalysts for hydrogen evolution were synthesized by a solvothermal and chemical adsorption method. CdS NRs coated by 5 wt% boron nitride (BN) shell exhibited remarkably visible-light photocatalytic hydrogen evolution activity of up to 30.68 mmol g⁻¹ h⁻¹, nearly 6.79 times higher than that of pure CdS NRs, and the apparent quantum efficiency at 420 nm was 7.5%. Transmission electron microscopy showed the CdS NRs were coated with a thin (~5 nm) BN layer, which together with the hydrogen evolution results proved the photocatalytic ability of CdS NRs was significantly improved. The hydrogen evolution rate of CdS NRs coated by 5 wt% BN remained at 91.4% after four cycles, indicating the photocorrosion of CdS NRs was effectively alleviated. Moreover, the large and close coaxial interfacial contact between the CdS core and the BN shell was beneficial to the separation and transfer of photogenerated electron-hole pairs.     

NiS2 Co-catalyst decoration on CdLa2S4 nanocrystals for efficient photocatalytic hydrogen generation under visible light irradiation

NiS₂ nanoparticles as noble metal-free co-catalysts were deposited onto the CdLa₂S₄ nanocrystals through a hydrothermal process. The loading of NiS₂ co-catalyst resulted in remarkable enhancement for H₂ production over the CdLa₂S₄ photocatalyst under visible light irradiation. The optimal hybrid photocatalyst with 2 wt% NiS₂ loading exhibited a H₂ production rate of 2.5 mmol h⁻¹ g⁻¹, which was more than 3 times higher than that of the pristine CdLa₂S₄ photocatalyst. The promoted photocatalytic H₂ production by NiS₂-loading is attributed to the enhanced separation of photogenerated electrons and holes as well as the activation effect of NiS₂ for H₂ evolution.     

Noble-metal-free Co@Co2P/N-doped carbon nanotube polyhedron as an efficient catalyst for hydrogen generation from ammonia borane

Developing an efficient catalyst for hydrogen (H₂) generation from hydrolysis of ammonia borane (AB) to significantly improve the activity for the hydrogen generation from AB is important for its practical application. Herein, we report a novel hybrid nanostructure composed of uniformly dispersed Co@Co₂P core-shell nanoparticles (NPs) embedded in N-doped carbon nanotube polyhedron (Co@Co₂P/N–CNP) through a carbonization-phosphidation strategy derived from ZIF-67. Benefiting from the electronic effect of P doping, high dispersibility and strong interfacial interaction between Co@Co₂P and N-CNTs, the Co@Co₂P/N–CNP catalyst exhibits excellent catalytic performance towards the hydrolysis of AB for hydrogen generation, affording a high TOF value of 18.4 mol H₂ mol metal^?1 min^?1 at the first cycle. This work provides a promising lead for the design of efficient heterogeneous catalysts towards convenient H₂ generation from hydrogen-rich substrates in the close future.     

Self-assembly core-shell BixY1-xVO4@g-C3N4 as an S-scheme heterojunction photocatalyst for pure water splitting

The self-assembly core-shell Bi_xY_1-xVO₄@g-C₃N₄ (BYVO@PCN) photocatalyst was synthesized by in-situ polycondensation of melamine on the surface of Bi_xY_1-xVO₄. The formation mechanism of the core-shell structure was mainly attributed to the excessive unpaired O atoms existed on the surface of BYVO, which could absorb the intermediate products of polycondensation. In addition, the core-shell BYVO@PCN can achieve photocatalytic pure water splitting into H₂ and O₂ which is about 5 times higher than the Bi_xY_1-xVO₄. Compared with PCN, BYVO@PCN tackles the problem that little O₂ evolution in pure water splitting by PCN. Furthermore, BYVO@PCN forms an S-scheme heterojunction instead of a type Ⅱ heterojunction, which significantly accelerates the separation of charge carriers.     

Employing one-step coupling cold plasma and thermal polymerization approach to construct nitrogen defect-rich carbon nitrides toward efficient visible-light-driven hydrogen generation

Construction of structural defects in photocatalysts is a powerful tool for regulating their photocatalytic performance. In this work, we develop a facile one-step coupling cold plasma and thermal polymerization approach to synthesize a series of nitrogen defect-rich graphitic carbon nitrides (C₃N_4-x), which are used for visible-light-driven hydrogen generation from water. The nitrogen defect-induced band structure regulation of C₃N_4-x catalysts can be carried out through controlling the bombardment time and excitation power of generator during the plasma modification process. The defective C₃N_4-x catalysts have the extended visible light absorption and improved separation efficiency of photogenerated charge carriers, which results in the boosted hydrogen generation activity. Particularly, the optimal C₃N_4-x possesses a hydrogen generation rate of 2.46 mmol h^?1 g^?1, which is about 4.5 times higher than the pristine C₃N₄ synthesized by the single thermal polymerization of urea. The cold plasma modification-based one-step synthesis approach guides us for rationally designing defective nanomaterials with excellent catalytic performance.     

Synthesis of carbon-doped SnO2 nanostructures for visible-light-driven photocatalytic hydrogen production from water splitting

Environmental issues: global warming, organic pollution, CO₂ emission, energy shortage, and fossil fuel depletion have become severe threats to the future development of humans. In this context, hydrogen production from water using solar light by photocatalytic/photoelectrochemical technologies, which results in zero CO₂ emission, has received considerable attention due to the abundance of solar radiation and water. Herein, a single-step thermal decomposition procedure to produce carbon-doped SnO₂ nanostructures (C–SnO₂) for photocatalytic applications is proposed. The visible-light-driven photocatalytic performance of the as-prepared materials is evaluated by photocatalytic hydrogen generation experiments. The bandgaps of the photocatalysts are determined by ultraviolet–visible diffused reflectance spectroscopy. The crystallinity, morphological features (size and shape), and chemical composition and elemental oxidation states of the samples are investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The proposed simple thermal decomposition method has significant potential for producing nanostructures for metal-free photocatalysis.     

In situ tuning of band gap of Sn doped composite for sustained photocatalytic hydrogen generation under visible light irradiation

The significance of Sn dopant on the photocatalytic performance of Iron/Titanium nanocomposite towards photocatalytic hydrogen generation by water splitting reaction is investigated. Iron/Titanium nanocomposite modified by Sn⁴⁺ dopant acts as a suitable photocatalyst for induced visible light absorption facilitating pronounced charge separation efficiency. Various characterization techniques reveal the heterojunction formation of hematite Fe₂O₃ with anatase - rutile mixed phase of TiO₂ employing Sn doping, where Sn⁴⁺ dopant accomplishes the phase transformation of anatase to rutile, entering into the TiO₂ lattice. This extended the lifetime of photogenerated charge carriers and enhanced the quantum efficiency of the photocatalyst. The band gap of the nanocomposite is tuned to ~2.4 eV, favoring visible light absorption. A hydrogen generation activity of 1102.8 μmol, approximately five times higher than the lone system (216.5 μmol) is achieved for the 5% Sn doped system for an average of 5 h. Heterojunctions of hematite with anatase-rutile mixed phase, generated as a consequence of tin doping facilitated the enhanced hydrogen generation activity of photocatalyst.     

Active-center-enriched Ni0.85Se/g-C3N4 S-scheme heterojunction for efficient photocatalytic H2 generation

Photocatalysts with abundant active sites are essential for photocatalytic H₂ evolution from water. Herein, Ni_0.85Se-deposited g-C₃N₄ was obtained by a physical solvent evaporation method. The investigation shows that Ni_0.85Se with unsaturated active Se atoms can significantly improve the photocatalytic activity of g-C₃N₄, and the H₂ production rate of Ni_0.85Se/g-C₃N₄ can reach 8780.3 μmol g^?1 h^?1, which is 3.5 and 92.9 times higher than that of Ni_0.85+xSe/g-C₃N₄ (2497.9 μmol g^?1 h^?1) and pure g-C₃N₄ (94.5 μmol g^?1 h^?1), respectively. This improvement can be attributed to the quick charge transfer between Ni_0.85Se and g-C₃N₄ with S-scheme heterojunction feature based on a series of trapping experiments and photoelectrochemical analysis. Moreover, abundant unsaturated Se atoms could provide more H₂ evolution active sites. This work sheds light on the construction of heterojunctions with abundant active sites for H₂ production.     

One-pot synthesis of CdS-MoS2/RGO-E nano-heterostructure with well-defined interfaces for efficient photocatalytic H2 evolution

Quality of interfaces is a key factor determining photoexcited charge transfer efficiency, and in turn photocatalytic performance of heterostructure photocatalysts. In this paper, we demonstrated CdS-MoS₂/RGO-E (RGO-E: reduced graphene oxide modified by ethylenediamine) nanohybrid synthesized by using a facile one-pot solvethermal method in ethylenediamine, with CdS nanoparticles and MoS₂ nanosheets intimately growing on the surface of RGO. This unique high quality heterostructure facilitates charge separation and transportation, and thus effectively suppressing charge recombination. As a result, the CdS-MoS₂/RGO-E exhibits a state-of-the-art H₂ evolution rate of 36.7 mmol g^?1 h^?1 and an apparent quantum yield of 30.5% at 420 nm, which is the advanced performance among all the same-type photocatalysts (see Table S1), and far exceeding that of bare CdS by higher than 104 times. This synthesis strategy gives an inspiration for the synthesis of other compound catalysts, and higher performance photocatalyst may be obtained.     

CuO@NiO core-shell nanoparticles decorated anatase TiO2 nanospheres for enhanced photocatalytic hydrogen production

Core-shell structured co-catalyst has been created much attention in photocatalytic hydrogen production due to their efficient electron-hole pair separation, suppression of surface back reaction and long term stability. Here, we report the preparation of CuO@NiO hierarchical nanostructures as a co-catalyst deposited on TiO₂ nanospheres for enhanced photocatalytic hydrogen generation. The formation of ultrathin NiO shell over the CuO core was confirmed by TEM analysis. Fabricated core-shell nanostructured CuO@NiO over TiO₂ nanospheres was studied for hydrogen evolution under the direct solar light and it showed a high rate of H₂ production of 26.1 mmol. h⁻¹. g⁻¹_cat. It was scrutinized that the rate of hydrogen production was improved with shell thickness and co-catalyst loading. Systematic investigation on CuO@NiO co-catalyst loading, pH of the medium and glycerol concentration for augmented H₂ production. The recorded rate of hydrogen production is almost six folds greater than that of pristine TiO₂. In the view of largescale synthesis for alternative energy storage applications, the composited photocatalyst was made of by simple mixing method, which could be scaled up without any loss in photocatalytic activity. Further, the stability test of photocatalyst for continuous use found that 82% of initial photocatalytic activity is retained even after three days.     

Significant improvement of TiO2 photocatalytic hydrogen generation by photothermic synergistic action and underlying mechanism

This article reported an extremely easy method of optical radiation-assisted thermal excitation to dramatically increase photocatalytic hydrogen generation ability of water splitting with P25 as a model compound. This method compensated for the time waste, high cost and operational complexity of traditional catalytic material modification methods, and largely improved the photocatalytic hydrogen production ability of photocatalytic materials. The hydrogen generation rates at room temperature is 1090 μmol/g/h. At 50 °C, the rate increase to 10670 μmol/g/h. The quantum rates at room temperature and 50 °C are 6.5 and 63.3, respectively. It is clear that appropriate low-temperature heating could largely accelerate the hydrogen generation rate of P25.This work presents the detailed mechanism how this method largely enhances photocatalytic hydrogen generation of P25 as well as the laws. The new method offers some evidences and reference for research on how the photothermic synergistic action facilitates the photocatalytic hydrogen generation of catalytic materials.     

Enhanced photocatalytic performance of chemically bonded SiC-graphene composites for visible-light-driven overall water splitting

Chemically bonded SiC-graphene composites were prepared by a chemical grafting method. The Si–C bonds between SiC and graphene can form a heterojunction interface. The chemical bonding and the heterojunction interface are beneficial to the quick transfer of photogenerated electrons from SiC to graphene and thus avoiding the recombination with holes. As a result, the composites show an enhanced activity (more than 90%) for photocatalytic splitting of water under visible light irradiation.     

A new insight into Au/TiO2-catalyzed hydrogen production from water-methanol mixture using lamps containing simultaneous ultraviolet and visible radiation

Different amounts of Au NPs were deposited on a modified-TiO₂ using the deposition-precipitation method with urea and used for hydrogen production via water splitting at room temperature and atmospheric pressure. Methanol and simultaneous UV and visible radiation were used as sacrificial reagent and excitation sources, respectively. Both modified-support and photocatalysts were characterized by XRD, HRTEM or STEM-HAADF, FE-SEM-EDS, N₂ physisorption and UV–vis DRS. The emission spectra of the excitation sources were also obtained by spectrofluorometry. XRD, HRTEM and UV–vis DRS results showed that TiO₂ anatase was the predominant crystalline phase, with a relative high specific surface area. STEM-HAADF and FE-SEM-EDS techniques revealed that the average Au NPs size was increased with Au loading from 3.2 to 14.9 nm and that the estimated Au contents were close to the expected theoretical values. On the other hand, the photo-generated hydrogen was significantly increased with Au NPs incorporation and it could be associated to a slightly decrease of the energy band gap and the intrinsic localized surface plasmon resonance that can suppress the high rate of electron-hole pair recombination. The photocatalytic performance also depended on multiples experimental factors, such as: stirring speed, amount and size of Au NPs, as well as the radiation source. The highest hydrogen production rate (2336 μmol-H₂/g_cat⋅h) was obtained using the Au/TiO₂ photocatalyst with 0.5 wt% Au, a stirring speed of 800 rpm and purple lamp (13 W) simultaneously emitting UV (52%) and visible (48%) radiation.