Boosted Hydrogen-Evolution Kinetics Over Particulate Lanthanum and Rhodium-Doped Strontium Titanate Photocatalysts Modified with Phosphonate Groups

Junction of ZnmIn2S3+m and bismuth vanadate as Z-scheme photocatalyst for enhanced hydrogen evolution activity: The role of interfacial interactions

A series of Zn_mIn₂S_3+m photocatalysts were synthesized to show tunable band gap energy with the variation of Zn/S atomic ratio. The junction of Zn_mIn₂S_3+m and BiVO₄ led to intimate interfacial contacts. Both experimental and theoretical results implied that electrons flowed from Zn_mIn₂S_3+m to BiVO₄ at the Zn_mIn₂S_3+m/BiVO₄ interface to form built-in electric field due to the variation of Fermi level, which promised Z scheme charge transfer feature for improving separation of charge carriers for enhanced photocatalytic performance. A higher degree of charge transfer process occurred for Zn₂In₂S₅/BiVO₄ heterostructure promised stronger built-in electric field, higher charge separation efficiency and improved photocatalytic activity in comparison to ZnIn₂S₄/BiVO₄ and Zn₃In₂S₆/BiVO₄ heterojunctions. The optimal hydrogen production rate of Zn₂In₂S₅/BiVO₄ photocatalyst is 8.42 mmol•g^-1•h^-1 with apparent quantum yield of 22.32 % at 435 nm, which is about 2.2 and 1.5 times higher than that of ZnIn₂S₄/BiVO₄ and Zn₃In₂S₆/BiVO₄, respectively.

One-Step MOF-Templated Strategy to Fabrication of Ce-Doped ZnIn2 S4 Tetrakaidecahedron Hollow Nanocages as an Efficient Photocatalyst for Hydrogen Evolution

Achieving structure optimizing and component regulation simultaneously in the ZnIn₂ S₄ -based photocatalytic system is an enormous challenge in improving its hydrogen evolution performance. 3D hollow-structured photocatalysts have been intensively studied due to their obvious advantages in solar energy conversion reactions. The synthesis of 3D hollow-structured ZnIn₂ S₄ , however, is limited by the lack of suitable template or synthesis methods, thereby restricting the wide application of ZnIn₂ S₄ in the field of photocatalysis. Herein, Ce-doped ZnIn₂ S₄ photocatalysts with hollow nanocages are obtained via one-step hydrothermal method with an ordered large-pore tetrakaidecahedron cerium-based metal-organic frameworks (Ce-MOFs) as template and Ce ion source. The doping of Ce and the formation of ZnIn₂ S₄ tetrakaidecahedron hollow nanocages with ultrathin nanosheet subunits are simultaneously induced by the Ce-MOFs, making this groundbreaking work. The Ce-doped ZnIn₂ S₄ with a nonspherical 3D hollow nanostructure inherit the tetrakaidecahedron shape of the Ce-MOF templates, and the shell is composed of ultrathin nanosheet subunits. Both theoretical and experimental results indicate that the doping of Ce and the formation of hollow nanocages increase light capture and the separation of photogenerated charge carriers.

Optimizing Atomic Hydrogen Desorption of Sulfur-Rich NiS1+ x Cocatalyst for Boosting Photocatalytic H2 Evolution

Low-cost transition-metal chalcogenides (MS_x ) are demonstrated to be potential candidate cocatalyst for photocatalytic H₂ generation. However, their H₂ -generation performance is limited by insufficient quantities of exposed sulfur (S) sites and their strong bonding with adsorbed hydrogen atoms (SH_ads ). To address these issues, an efficient coupling strategy of active-site-enriched regulation and electronic structure modification of active S sites is developed by rational design of core-shell Au@NiS_{1+ x} nanostructured cocatalyst. In this case, the Au@NiS_{1+ x} cocatalyst can be skillfully fabricated to synthesize the Au@NiS_{1+ x} modified TiO₂ (denoted as TiO₂ /Au@NiS_{1+ x} ) by a two-step route. Photocatalytic experiments exhibit that the resulting TiO₂ /Au@NiS_{1+ x} (1.7:1.3) displays a boosted H₂ -generation rate of 9616 µmol h^-1 g^-1 with an apparent quantum efficiency of 46.0%  at 365 nm, which is 2.9 and 1.7 times the rate over TiO₂ /NiS_{1+ x} and TiO₂ /Au, respectively. In situ/ex situ XPS characterization and density functional theory calculations reveal that the free-electrons of Au can transfer to sulfur-enriched NiS_{1+ x} to induce the generation of electron-enriched S^{δ -} active centers, which boosts the desorption of H_ads for rapid hydrogen formation via weakening the strong SH_ads bonds. Hence, an electron-enriched S^{δ -} -mediated mechanism is proposed. This work delivers a universal strategy for simultaneously increasing the active site number and optimizing the binding strength between the active sites and hydrogen adsorbates.