Defective Carbon Nitride with Dual-surface Engineering\nfor Highly Efficient Photocatalytic Hydrogen Evolution under Visible\nLight Irradiation

Defective\ncarbon nitride (DCN-<i>x</i>) was synthesized\nthrough a dual-surface engineering process consisting of nitric acid\ntreatment followed by high-temperature calcination. This process endowed\nDCN-<i>x</i> with a porous structure and a larger surface\narea than that of pure graphite carbon nitride (CN), enhancing its\nvisible light absorption and reducing the electron–hole recombination\nrate. Consequently, DCN-<i>x</i> demonstrated a significantly\nmore efficient photocatalytic hydrogen evolution, with the optimum\nsample, DCN-600, achieving an activity 55.9 times greater than that\nof pure CN, while maintaining excellent photocatalytic stability.\nFurthermore, the presence of tri-s-triazine (heptazine) structures\nwithin the CN’s in-plane structure was identified as a critical\nfactor for band gap optimization, suggesting new avenues for the synthesis\nof carbon nitride variants with enhanced photocatalytic performance.