Optimizing Atomic Hydrogen Desorption of Sulfur‐Rich NiS₁₊<i>_x</i> Cocatalyst for Boosting Photocatalytic H₂ Evolution

Abstract

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@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 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.