Retorting Photocorrosion and Enhanced Charge Carrier Separation at CdSe Nanocapsules by Chemically Synthesized TiO 2 Shell for Photocatalytic Hydrogen Fuel Generation

Metal chalcogenide-based core/shell photocatalysts for solar hydrogen production: Recent advances, properties and technology challenges

Metal chalcogenides play a vital role in the conversion of solar energy into hydrogen fuel. Hydrogen fuel technology can possibly tackle the future energy crises by replacing carbon fuels such as petroleum, diesel and kerosene, owning to zero emission carbon-free gas and eco-friendliness. Metal chalcogenides are classified into narrow band gap (CdS, Cu₂S, Bi₂S_3, MoS_2, CdSe and MoSe₂) materials and wide band gap materials (ZnS, ZnSe and ZnTe). Composites of these materials are fabricated with different architectures in which core-shell is one of the unique composites that drastically improve the photo-excitons separation, where chalcogenides in the core can be well protected for sustainable uses. Thus,the core-shell structures promote the design and fabrication of composites with the required characteristics. Interestingly, the metal chalcogenides as a core-shell photocatalyst can be classified into type-I, reverse type-I, type-II and S-type nanocomposites, which can effectively influence and significantly enhance the rate of hydrogen production. In this direction, this review is undertaken to provide a comprehensive overview of the advanced preparation processes, properties of metal chalcogenides, and in particular, photocatalytic performance of the metal chalcogenides as a core-shell photocatalysts for solar hydrogen production.

Hierarchical Co0.85 Se-CdSe/MoSe2 /CdSe Sandwich-Like Heterostructured Cages for Efficient Photocatalytic CO2 Reduction

Fabricating efficient photocatalysts with rapid charge carrier separation and high visible light harvesting is an advisable strategy to improve CO₂ reduction performance. Herein, hierarchical Co_0.85 Se-CdSe/MoSe₂ /CdSe cages with sandwich-like heterostructure are prepared to act as efficient photocatalysts for CO₂ reduction. In this study, the structure and composition of the final products can be regulated through the cation-exchange reaction in the presence of ascorbic acid. In the Co_0.85 Se-CdSe/MoSe₂ /CdSe cages, MoSe₂ nanosheets function as a bridge to integrate Co_0.85 Se-CdSe and CdSe on both sides of the MoSe₂ nanosheet shell into a sandwich-like heterostructured catalyst system, which possesses multiple positive merits for photocatalysis, including accelerated transport and separation of photogenerated carriers, improved visible light utilization, and increased catalytic active sites. Thus, the optimized Co_0.85 Se-CdSe/MoSe₂ /CdSe cages exhibit remarkable visible-light photocatalytic performance and outstanding stability for CO₂ reduction with a high CO average yield of 15.04 µmol g^-1 h^-1 and 90.14% selectivity, which are much higher than those of other control samples including single-component catalysts and binary hybrid catalysts. This study provides a promising way for the design and fabrication of high-efficiency photocatalysts.

Monodispersed core/shell nanospheres of ZnS/NiO with enhanced H2 generation and quantum efficiency at versatile photocatalytic conditions

This investigation is first to elucidate the synthesis of mono-dispersed ZnS/NiO-core/shell nanostructures with a uniform thin layer of NiO-shell on the ZnS-nanospheres as a core under controlled thermal treatments. NiO-shell thickness varied to 8.2, 12.4, 18.2, and 24.2 nm, while the ZnS-core diameter remained stable about 96 ± 6 nm. The crystalline phase and core/shell structure of the materials were confirmed using XRD and HRTEM techniques, respectively. Optical properties through UV-vis spectroscopy analysis revealed the manifestation of red-shift in the absorption spectrum of core/shell materials, while the XPS analysis of elements elucidated their stable oxidation states in ZnS/NiO core/shell structure. The optimized ZnS/NiO-core/shell showed 1.42 times higher H₂ generation (162.1 mmol h^-1 g^-1_cat) than the pristine ZnS-core (113.2 mmol h^-1 g^-1_cat), and 64.5 times higher than the pristine NiO-shell (2.5 mmol h^-1 g^-1_cat). The quantum efficiency at wavelengths of 420, 365 nm, and 1.5 G air mass filters was found to be 13.5%, 25.0%, and 45.3%, respectively. Water splitting experiments was also performed without addition of any additives, which showed enhanced H₂ gas evolution of 1.6 mmol h^-1 g^-1_cat under the sunlight illumination. Photoelectrochemical measurements revealed the stable photocurrent density and minimized charge recombination in the system. The performed recyclability and reusability tests for five recycles demonstrated the excellent stability of the developed photocatalysts.

Chalcogenides as photocatalysts

Chalcogenides and chalcogenide-based heterostructures as photocatalysts.