Synergistic N 2C and NH x Vacancies in 2D g-C 3 N 4 Optimize the Oxygen Reduction Pathway for Efficient H 2 O 2 Photosynthesis

The photocatalytic two-electron oxygen reduction reaction (2e – ORR) for hydrogen peroxide (H 2 O 2 ) production is a green and promising route, yet the development of efficient photocatalysts remains challenging. While defect-engineered graphitic carbon nitride (g-C 3 N 4 ) has shown potential, the specific roles of defect sites in the interfacial reaction mechanism for the 2e – ORR are still unclear. Herein, we report a two-dimensional g-C 3 N 4 rich in nitrogen vacancies (2D-NvCN) via thermal exfoliation and an argon etching strategy. The optimized 2D-NvCN catalyst, featuring concurrently introduced N 2C and NH x vacancies, exhibits a remarkable H 2 O 2 generation rate under visible light, which is 13.3 times higher than that of its pristine counterpart. Crucially, combined experimental characterization and theoretical calculations elucidate the distinct and synergistic roles of these vacancies: the N 2C sites serve as primary centers for O 2 adsorption and activation, effectively suppressing the formation of undesired reactive oxygen species ( · O 2 –, 1 O 2 ), while the NH x vacancies significantly modulate the electronic structure, enhancing charge separation efficiency. This synergy optimizes the 2e – ORR pathway, providing fundamental insights into the rational design of high-performance catalytic materials via defect engineering for energy conversion and environmental remediation.