Trace water triggers high-efficiency photocatalytic hydrogen peroxide production

Abstract 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 · OOH radicals through hydrogen bond, while trace water could trigger photocatalytic production of H2O2 via providing and transferring indispensable free protons to completely consume · OOH radicals, which breaks the reaction balance of · OOH radical generation from alcohol. Thus · 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.