Trace water triggers high-efficiency photocatalytic hydrogen peroxide production

Photocatalytic production of hydrogen peroxide (H2O2) has attracted much attentions as a promising method for sustainable solar fuel. Here, we demonstrate that trace water can drastically boost high-efficiency photocatalytic production of H2O2 with a record-high concentration of 113 mmol L-1 using alkali-assisted C3N4 as photocatalyst in water/alcohol mixture solvents. By electron paramagnetic resonance (EPR) measurement, the radical species generated during the photocatalytic process of H2O2 are identified. We propose alcohol is used to provide and stabilize center dot OOH radicals through hydrogen bond, while trace water could trigger photocatalytic production of H2O2 via providing and transferring indispensable free protons to completely consume center dot OOH radicals, which breaks the reaction balance of center dot OOH radical generation from alcohol. Thus center dot OOH radicals could be supplied by alcohol continuously to serve as a reservoir for high-efficiency production of H2O2. These results pave the way towards photocatalytic method on semiconductor catalysts as an outstanding approach for production of hydrogen peroxide. (C)2021 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.