Defective
carbon nitride (DCN-x) was synthesized
through a dual-surface engineering process consisting of nitric acid
treatment followed by high-temperature calcination. This process endowed
DCN-x 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-x 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.