Promoting Proton Donation through Hydrogen Bond Breaking on Carbon Nitride for Enhanced HO Photosynthesis.

Photocatalytic HO production has attracted much attention as an alternative way to the industrial anthraquinone oxidation process but is limited by the weak interaction between the catalysts and reactants as well as inefficient proton transfer. Herein, we report on a hydrogen-bond-broken strategy in carbon nitride for the enhancement of HO photosynthesis without any sacrificial agent. The HO photosynthesis is promoted by the hydrogen bond formation between the exposed N atoms on hydrogen-bond-broken carbon nitride and HO molecules, which enhances proton-coupled electron transfer and therefore the photocatalytic activity. The exposed N atoms serve as proton buffering sites for the proton transfer from HO molecules to carbon nitride. The HO photosynthesis is also enhanced through the enhanced adsorption and reduction of O gas toward HO on hydrogen-bond-broken carbon nitride because of the formation of nitrogen vacancies (NVs) and cyano groups after the intralayer hydrogen bond breaking on carbon nitride. A high light-to-chemical conversion efficiency (LCCE) value of 3.85% is achieved. O and HO molecules are found to undergo a one-step two-electron reduction pathway by photogenerated hot electrons and a four-electron oxidation process to produce O gas, respectively. Density functional theory (DFT) calculations validate the O adsorption and reaction pathways. This study elucidates the significance of the hydrogen bond formation between the catalyst and reactants, which greatly increases the proton tunneling dynamics.