H₂O₂ Production via Artificial Photosynthesis Over Defective Graphitic Carbon Nitride

Metal-free graphitic carbon nitride has been considered as a promising candidate for hydrogen peroxide (H₂O₂) photosynthesis, with the advantage of low-cost, high stability, and environmentally friendly capacity. However, such a solar-to-chemical conversion still suffers from limited light utilization, confined surface adsorption, and restricted reduction/oxidation reaction pathway. At this juncture, this bottleneck has been overcome through diverse modifications over carbon nitride, such as defect engineering graphitic carbon nitride with modulated physical and chemical properties, which performs satisfactory visible-light absorption, sufficient active sites, and promotes charge transfer kinetics for artificial solar-to-chemical conversion. In this review, the recent advances for H₂O₂ photosynthesis over defective graphitic carbon nitride are described, including the existing principles for H₂O₂ formation, the factors affecting photosynthesis, the fabrication strategies toward novel materials, and the detailed pathways for H₂O₂ formation. The functions of defects, the properties of materials, and the reaction mechanisms, and the selectivity, as well as in situ characterizations for catalyst synthesis and pathway exploration, have been summarized clearly. Finally, the advantages and shortcomings, together with the challenges and prospects, are highlighted for the development of defect engineering over carbon nitride for H₂O₂ photosynthesis.