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 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Hads ). 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 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 /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 Sδ - active centers, which boosts the desorption of Hads for rapid hydrogen formation via weakening the strong SHads bonds. Hence, an electron-enriched Sδ - -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.