Simultaneously Tuning Band Structure and Oxygen Reduction Pathway toward High-Efficient Photocatalytic Hydrogen Peroxide Production Using Cyano-Rich Graphitic Carbon Nitride

The demands for green production of hydrogen peroxide have triggered extensive studies in the photocatalytic synthesis, but most photocatalysts suffer from rapid charge recombination and poor 2e^? oxygen reduction reaction (ORR) selectivity. Here, a novel composite photocatalyst of cyano-rich graphitic carbon nitride g-C₃N₄ is fabricated in a facile manner by sodium chloride-assisted calcination on dicyandiamide. The obtained photocatalysts exhibit superior activity (7.01 mm  h^?1 under λ  ≥  420 nm, 16.05 mm  h^?1 under simulated sun conditions) for H₂O₂ production and 93% selectivity for 2e^? ORR, much higher than that of the state-of-the-art photocatalyst. The porous g-C₃N₄ with Na dopants and cyano groups simultaneously optimize two limiting steps of the photocatalytic 2e^? ORR: photoactivity, and selectivity. The cyano groups can adjust the band structure of g-C₃N₄ to achieve high activity. They also serve as oxygen adsorption sites, in which local charge polarization facilitates O₂ adsorption and protonation. With the aid of Na⁺, the O₂ is reduced to produce more superoxide radicals as the intermediate products for H₂O₂ synthesis. This work provides a facile approach to simultaneously tune photocatalytic activity and 2e^? ORR selectivity for boosting H₂O₂ production, and then paves the way for the practical application of g-C₃N₄ in environmental remediation and energy supply.