How melamine thermolysis conditions influence energy vs electron transfer in g-C3N4 photocatalysis

Graphitic carbon nitride (g-C 3 N 4 ) is a versatile photocatalyst capable of mediating both electron-transfer (ET) and energy-transfer (EnT) reactions, yet the factors determining which pathway dominates remain unclear. Here, more than 30 g-C 3 N 4 samples were systematically synthesized under varied thermolysis conditions, including precursor composition, calcination temperature, heating rate, crucible coverage, and metal doping, in order to elucidate how these parameters influence structure, defects, and photocatalytic behavior. Subtle variations in synthesis produced pronounced differences in photoactivity, revealing that oxygen incorporation and defect location critically regulate reaction pathways. Bulk oxygen defects stabilize excitons and enhance ET efficiency, whereas surface oxygen promotes recombination and favors EnT. Cu and Ni dopants further tune these mechanisms by modifying exciton dynamics through coordination and electron-trapping effects. Time-resolved photoluminescence analysis shows that shorter lifetimes generally correlate with stronger EnT performance, offering a simple screening metric for mechanism-specific activity. These findings highlight that photocatalytic efficiency arises from a delicate balance between structure, defects, and exciton dynamics, emphasizing that successful catalyst design depends not on finding a single “best” material but on choosing the right one for the right reaction.