Boosting Photocatalytic Water Oxidation Over Bifunctional Rh⁰‐Rh³⁺ Sites

Abstract Photocatalytic water splitting provides an economically feasible way for converting solar energy into hydrogen. Great efforts have been devoted to developing efficient photocatalysts; however, the surface catalytic reactions, especially for the sluggish oxygen evolution reaction (OER), still remain a challenge, which limits the overall photocatalytic energy efficiency. Herein, we design a Rh n cluster cocatalyst, with Rh 0 ‐Rh 3+ sites anchoring the Mo‐doped BiVO 4 model photocatalytic system. The resultant photocatalyst enables a high visible‐light photocatalytic oxygen production activity of 7.11 mmol g −1 h −1 and an apparent quantum efficiency of 29.37 % at 420 nm. The turnover frequency (TOF) achieves 416.73 h −1 , which is 378 times higher than that of the photocatalyst only with Rh 3+ species. Operando X‐ray absorption characterization shows the OER process on the Rh 0 ‐Rh 3+ sites. The DFT calculations further illustrate a bifunctional OER mechanism over the Rh 0 ‐Rh 3+ sites, in which the oxygen intermediate attacks the Rh 3+ sites with assistance of a hydrogen atom transfer to the Rh 0 sites, thus breaking the scaling relationship of various oxygen intermediates.