Layer WidthEngineering in Carbon Nitride for EnhancedExciton Dissociation and Solar Fuel Generation

Photocatalytic H₂ and H₂O₂ production using graphitic carbon nitride (<i>g</i>-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 <i>g</i>-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 <i>g</i>-C₃N₄ in H₂ and H₂O₂ production rates, respectively, under visible light. Considering the earth-abundant constituents of <i>g</i>-C₃N₄, our work establishes a novel design strategy for a highly active, sustainable photocatalyst.