Photocatalytic HO production over boron-doped g-CN containing coordinatively unsaturated FeOOH sites and CoO clusters.

Graphitic carbon nitride (g-CN) has gained increasing attention in artificial photosynthesis of HO, yet its performance is hindered by sluggish oxygen reduction reaction (ORR) kinetics and short excited-state electron lifetimes. Here we show a B-doped g-CN (BCN) tailored with coordinatively unsaturated FeOOH and CoO clusters for HO photosynthesis from water and oxygen without sacrificial agents. The optimal material delivers a 30-fold activity enhancement compared with g-CN under visible light, with a solar-to-chemical conversion efficiency of 0.75%, ranking among the forefront of reported g-CN-based photocatalysts. Additionally, an electron transfer efficiency reaches 34.1% for the oxygen reduction reaction as revealed by in situ microsecond transient absorption spectroscopy. Experimental and theoretical results reveal that CoO initiates hole-water oxidation and prolongs the electron lifetime, whereas FeOOH accepts electrons and promotes oxygen activation. Intriguingly, the key to the direct one-step two-electron reaction pathway for HO production lies in coordinatively unsaturated FeOOH to adjust the Pauling-type adsorption configuration of O to stabilize peroxide species and restrain the formation of superoxide radicals.