Promoted Hydrogen Peroxide Production from Pure Water on g-C3N4 with Nitrogen Defects Constructed through Solvent-Precursor Interactions: Exploring a Complex Story in Piezo-Photocatalysis.

Hydrogen peroxide (H₂O₂) production via oxygen (O₂) reduction reaction (ORR) in pure water (H₂O) through graphitic carbon nitrides (g-C₃N₄)-based piezo-photocatalysts is an exciting approach in many current studies. However, the low Lewis-acid properties of g-C₃N₄ limited the catalytic performance because of the low O₂ adsorption efficacy. To overcome this challenge, the interaction of g-C₃N₄ precursors with various solvents are utilized to synthesize g-C₃N₄, possessing multiple nitrogen-vacant species via thermal shocking polymerization. These results suggest that the lack of nitrogen in g-C₃N₄ and the incident introduction of oxygen-functional groups enhance the Lewis acid-base interactions and polarize the g-C₃N₄ lattices, leading to the enormous enhancement. Furthermore, the catalytic mechanisms are thoroughly studied, with the formation of H₂O₂ proceeding via radical and water oxidation pathways, in which the roles of light and ultrasound are carefully investigated. Thus, these findings not only reinforce the potential view of metal-free photocatalysts, accelerating the understanding of g-C₃N₄ working principles to generate H₂O₂ based on the oxygen reduction and water oxidation reactions, but also propose a facile one-step way for fabricating highly efficient and scalable photocatalysts to produce H₂O₂ without using sacrificial agents, pushing the practical application of in situ solar H₂O₂ toward real-world scenarios.