Synergistic Defect Sites and CoO x Nanoclusters in Polymeric Carbon Nitride for Enhanced Photocatalytic H2O2 Production

The photocatalytic two-electron O-2 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 O-2 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 O-2 to H2O2, synergistically improving the activity and selectivity of H2O2 production. The designed photocatalyst (CoOx-NvCN) achieves a H2O2 production rate of 244.8 mu mol 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 O-2 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.