Synergy of nitrogen vacancies and partially broken hydrogen bonds in graphitic carbon nitride for superior photocatalytic hydrogen evolution under visible light

Abstract

Hydrogen-bond engineering and nitrogen vacancies have been proposed separately to significantly tune the photoactivities of g-C₃N₄. Nevertheless, the intrinsic relationships between hydrogen bonds, nitrogen vacancies and photo-performance are still unclear. Herein, partially broken hydrogen bonds and nitrogen vacancies were simultaneously introduced into a g-C₃N₄ framework (BNCNx) via a facile magnesium-etching approach. BNCN20 showed a remarkably high hydrogen evolution rate of 1941.7 μmol h⁻¹ g⁻¹ under λ >400 nm irradiation with satisfactory photostability, which was respectively 13 times and 3 times that of g-C₃N₄ with hydrogen bonds (HCN) and g-C₃N₄ with partially broken hydrogen bonds (BCN), as well as higher than that of most reported metal-free g-C₃N₄ photocatalysts. The apparent quantum efficiencies (AQEs) of BNCN20 at 405 and 420 nm were 9.58% and 8.57%, respectively. This work demonstrated that the synergy of partially broken hydrogen bonds and nitrogen defects was an effective strategy to engineer the electronic structures of g-C₃N₄ with outstanding physicochemical properties for photocatalysis.