Protruding Pt single-sites on hexagonal ZnIn₂S₄ to accelerate photocatalytic hydrogen evolution

Single-site cocatalysts engineered on supports offer a cost-efficient pathway to utilize precious metals, yet improving the performance further with minimal catalyst loading is still highly desirable. Here we have conducted a photochemical reaction to stabilize ultralow Pt co-catalysts (0.26 wt%) onto the basal plane of hexagonal ZnIn₂S₄ nanosheets (Pt_SS-ZIS) to form a Pt-S₃ protrusion tetrahedron coordination structure. Compared with the traditional defect-trapped Pt single-site counterparts, the protruding Pt single-sites on h-ZIS photocatalyst enhance the H₂ evolution yield rate by a factor of 2.2, which could reach 17.5 mmol g^-1 h^-1 under visible light irradiation. Importantly, through simple drop-casting, a thin Pt_SS-ZIS film is prepared, and large amount of observable H₂ bubbles are generated, providing great potential for practical solar-light-driven H₂ production. The protruding single Pt atoms in Pt_SS-ZIS could inhibit the recombination of electron-hole pairs and cause a tip effect to optimize the adsorption/desorption behavior of H through effective proton mass transfer, which synergistically promote reaction thermodynamics and kinetics.