Photocatalytic H2O2 production over boron-doped g-C3N4 containing coordinatively unsaturated FeOOH sites and CoO x clusters

Abstract

Abstract Graphitic carbon nitride (g-C3N4) has gained increasing attention in artificial photosynthesis of H2O2, 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-C3N4 (BCN) tailored with coordinatively unsaturated FeOOH and CoO x clusters for H2O2 photosynthesis from water and oxygen without sacrificial agents. The optimal material delivers a 30-fold activity enhancement compared with g-C3N4 under visible light, with a solar-to-chemical conversion efficiency of 0.75%, ranking among the forefront of reported g-C3N4-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 x 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 H2O2 production lies in coordinatively unsaturated FeOOH to adjust the Pauling-type adsorption configuration of O2 to stabilize peroxide species and restrain the formation of superoxide radicals.