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

Low-cost transition-metal chalcogenides (MSx) are demonstrated to be potential candidate cocatalyst for photocatalytic H-2 generation. However, their H-2-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@NiS1+x nanostructured cocatalyst. In this case, the Au@NiS1+x cocatalyst can be skillfully fabricated to synthesize the Au@NiS1+x modified TiO2 (denoted as TiO2/Au@NiS1+x) by a two-step route. Photocatalytic experiments exhibit that the resulting TiO2/Au@NiS1+x(1.7:1.3) displays a boosted H-2-generation rate of 9616 mu mol 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/NiS1+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 NiS1+x to induce the generation of electron-enriched S-delta(-) 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-delta(-)-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.

Automated summary

An efficient coupling strategy of active-site-enriched regulation and electronic structure modification is developed by rational design of core-shell Au@NiS1+x nanostructured cocatalyst to address the limited H-2-generation performance of transition-metal chalcogenides. The resulting TiO2/Au@NiS1+x(1.7:1.3) exhibits a boosted H-2-generation rate with improved apparent quantum efficiency, indicating potential for enhancing photocatalytic hydrogen generation.