Engineering Nitrogen Vacancies in Polymeric Carbon Nitride to Promote Interfacial Electron Transfer for Visible-Light Driven Hydrogen Evolution.

Polymeric carbon nitride (g-C3N4, GCN) is a highly promising metal-free photocatalyst for solar hydrogen production. However, its activity is still constrained by insufficient visible-light absorption and poor interlayer charge transport. Defect engineering of GCN has been widely deployed to promote photocatalytic hydrogen evolution efficiency, but a significant knowledge gap persists in linking specific defect structures to performance outcomes, and underlying mechanisms remain inadequately explored. Herein, we propose a controllable nitrogen-vacancy engineering strategy for GCN that induces interlayer contraction, thereby promoting interfacial charge transport. The tailored nitrogen vacancies broaden optical absorption, enhance interlayer electronic coupling, suppress charge carrier recombination, and lower the out-of-plane charge-transfer barrier. Consequently, the optimized photocatalyst exhibits a ∼ 23-fold enhancement in the hydrogen evolution rate compared to pristine GCN, while maintaining excellent stability over 50 h of continuous illumination. This work establishes a viable regulation strategy of nitrogen vacancies for advancing g-C3N4-based photocatalysts toward large-scale solar hydrogen production.