A Synchronous d-p Hybridization and Protonated State Regulation Strategy for Efficient HO Photosynthesis through Optimized Water Oxidation.

Photocatalytic HO synthesis  with Fe-based cocatalysts is sustainable but limited by sluggish water oxidation reaction (WOR) kinetics and low selectivity from weak *OH intermediate adsorption and instability. To address this, a "Fe-O-P d-p hybridization synergistic protonated state regulation" strategy is devised to enhance the WOR rate and HO selectivity. A dual-cocatalyst FeOOH/BiVO/Au, synthesized via two-step photodeposition, optimizes active sites and suppress charge recombination, with Au as oxygen reduction reaction active sites while FeOOH as WOR active sites. Subsequent phosphoric acid impregnation generates HPO @FeOOH/BiVO/Au, wherein Fe-O-P d-p hybridization modulates *OH adsorption and protonation state regulation enhances selectivity toward the two-electron WOR pathway. The optimized HPO @FeOOH(1%)/BiVO/Au(3%) catalyst achieved a high HO yield of 2321 μmol L in 3 h, 6 times higher than FeOOH/BiVO/Au, and the best among reported Bi-based photocatalysts under pure water. Density functional theory and in situ Fourier transform infrared spectroscopy showed that Fe-O-P hybridization raises the Fe d-band center and strengthens *OH adsorption, accelerating electron transfer during WOR. This work offers a new design concept for efficient WOR cocatalysts to boost photocatalytic HO production.