Photocatalytic H<sub>2</sub>O<sub>2</sub> production over boron-doped g-C<sub>3</sub>N<sub>4</sub> containing coordinatively unsaturated FeOOH sites and CoO<sub>x</sub> clusters.

Liu, Ping; Liang, Teng; Li, Yutong; Zhang, Ziqing; Li, Zhuo; Bian, Ji; Jing, Liqiang · Nat Commun · 2024

basic_science · Level V

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Abstract

Graphitic carbon nitride (g-C<sub>3</sub>N<sub>4</sub>) has gained increasing attention in artificial photosynthesis of H<sub>2</sub>O<sub>2</sub>, 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-C<sub>3</sub>N<sub>4</sub> (BCN) tailored with coordinatively unsaturated FeOOH and CoO<sub>x</sub> clusters for H<sub>2</sub>O<sub>2</sub> photosynthesis from water and oxygen without sacrificial agents. The optimal material delivers a 30-fold activity enhancement compared with g-C<sub>3</sub>N<sub>4</sub> under visible light, with a solar-to-chemical conversion efficiency of 0.75%, ranking among the forefront of reported g-C<sub>3</sub>N<sub>4</sub>-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<sub>x</sub> 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 H<sub>2</sub>O<sub>2</sub> production lies in coordinatively unsaturated FeOOH to adjust the Pauling-type adsorption configuration of O<sub>2</sub> to stabilize peroxide species and restrain the formation of superoxide radicals.