Layer Width Engineering in Carbon Nitride for Enhanced Exciton Dissociation and Solar Fuel Generation

Photocatalytic H2 and H2O2 production using graphitic carbon nitride (g-C3N4) offers promising renewable energy prospects but suffers from rapid exciton recombination, which can be mitigated by K+-insertion-driven enhanced interlayer electron–hole separation. However, limited K+ insertion remains a bottleneck due to inadequate ion-insertion channels. Herein, we present an engineered g-C3N4 with expanded layer widths for facile ion diffusion, increasing K+ insertion by >250%. This leads to significant layer contraction post K+ insertion (∼3%, 1.5 times larger than before) due to stronger electrostatic attraction, resulting in weaker exciton binding energy (91 meV, ∼57% diminished), near-complete suppression of photoluminescence, and doubling of excited-state electron lifetime as revealed by femtosecond decay kinetics. These improvements led to ∼25 and ∼140 times increments over bare g-C3N4 in H2 and H2O2 production rates, respectively, under visible light. Considering the earth-abundant constituents of g-C3N4, our work establishes a novel design strategy for a highly active, sustainable photocatalyst.