Breaking Oxygen\nEvolution Limits on Metal Chalcogenide\nPhotocatalysts for Visible-Light-Driven Overall Water-Splitting

Metal chalcogenides are promising visible-light absorption\nmaterials;\nhowever, their application in overall water-splitting has long been\nhampered by the sluggish kinetics of oxygen evolution reaction (OER)\nand serious photocorrosion. Fundamentally, these critical issues are\nrelated to the behavior of photogenerated holes. Here, using ZnSe\nas a model catalyst, we achieve high-performance overall water-splitting\nin intrinsic activity and stability by facilitating the utilization\nof holes in the OER rather than self-corrosion. This is guided by\nour microkinetic analysis that the kinetic bottleneck of hole-mediated\nOER on ZnSe is the high reaction barrier and low concentration of\nholes reaching the photocatalyst surface. Accordingly, we radically\nmodify the conduction characteristic of ZnSe surface layer into <i>p</i>-type to break the above OER bottleneck. The resulting\nZnSe photocatalyst exhibits an impressive overall water-splitting\nperformance in pure water with an ideal H<sub>2</sub>/O<sub>2</sub> molar ratio of ∼2 and a solar-to-hydrogen conversion efficiency\nof 0.1891% without the assistance of any cocatalyst, outperforming\never-reported overall water-splitting of state-of-the-art metal chalcogenides\nunder identical conditions. In addition, due to the greatly promoted\nOER, the critical photocorrosion issue is successfully suppressed\non the engineered ZnSe photocatalyst. This work breaks the long-standing\nlimitations of metal chalcogenides for overall water-splitting.