Defective Carbon Nitride with Dual-surface Engineering for Highly Efficient Photocatalytic Hydrogen Evolution under Visible Light Irradiation

Defective carbon nitride (DCN-<i>x</i>) was synthesized through a dual-surface engineering process consisting of nitric acid treatment followed by high-temperature calcination. This process endowed DCN-<i>x</i> with a porous structure and a larger surface area than that of pure graphite carbon nitride (CN), enhancing its visible light absorption and reducing the electron-hole recombination rate. Consequently, DCN-<i>x</i> demonstrated a significantly more efficient photocatalytic hydrogen evolution, with the optimum sample, DCN-600, achieving an activity 55.9 times greater than that of pure CN, while maintaining excellent photocatalytic stability. Furthermore, the presence of tri-s-triazine (heptazine) structures within the CN's in-plane structure was identified as a critical factor for band gap optimization, suggesting new avenues for the synthesis of carbon nitride variants with enhanced photocatalytic performance.