Modulating the Structure of Graphitic Carbon Nitride for Accelerated Charge Separation and Enhanced Hydrogen Evolution

Graphitic carbon nitride (CN) is considered a promising metal-free photocatalyst due to its adjustable electronic band structure and straightforward synthesis. Nevertheless, the practical utility of pristine CN is hindered by its rapid carrier recombination rate and low electrical conductivity. In this study, we enhanced CN’s molecular structure through copolymerization with organic molecules, thereby optimizing its crystallinity, resulting in significant improvements. The optimized photocatalyst, termed CNBM, demonstrated a remarkable hydrogen evolution rate of 23.13 mmol·h−1·g−1, a 118-fold increase compared to CN, with an apparent quantum efficiency of 87.9% at 420 nm. This notable enhancement in photocatalytic performance can be attributed to the increased surface area, providing more active sites, and the incorporation of barbituric acid through copolymerization into the CN framework, facilitating electron delocalization. Furthermore, the enhanced crystallinity of CNBM promotes the effective separation of photogenerated electron–hole pairs.