Synergistic Defect Sites and CoO_<i>x</i> Nanoclusters in Polymeric Carbon Nitride for Enhanced Photocatalytic H₂O₂ Production

Abstract

The photocatalytic two-electron O2 reduction reaction (2e– ORR) for high-value hydrogen peroxide (H2O2) production is attracting widespread attention as a green and promising research pathway. Despite multiple optimization strategies, the current 2e– ORR systems remain constrained by photogenerated carrier recombination and slow O2 reduction kinetics. Therefore, a refined photocatalyst design is urgently needed to overcome these constraints, enabling enhanced H2O2 activity and deeper exploration of reaction mechanisms. Here, we design surface defect sites (N vacancies) and oxygen-affine CoOx nanoclusters on polymeric carbon nitride (CN) to break through the above limitations for enhanced photocatalytic H2O2 production. The introduction of N vacancies significantly enhances the photogenerated carrier separation, and highly active CoOx nanoclusters optimize the surface reaction process from O2 to H2O2, synergistically improving the activity and selectivity of H2O2 production. The designed photocatalyst (CoOx-NvCN) achieves a H2O2 production rate of 244.8 μmol L–1 h–1 in pure water, with an apparent quantum yield (AQY) of 5.73% at 420 nm and a solar-to-chemical energy conversion (SCC) efficiency of 0.47%, surpassing previously reported CN-based photocatalysts. Importantly, experiments and theoretical calculations reveal that N vacancies optimize the photoelectronic response characteristics of the CN substrate, while the CoOx nanoclusters promote O2 adsorption and activation, reducing the formation energy barrier for crucial intermediate *OOH, thereby accelerating H2O2 generation. This work provides a feasible approach to the photocatalyst design strategy that simultaneously facilitates photogenerated carrier separation and effective active sites for high-performance H2O2 production.