Amorphous Carbon Nitride with Three Coordinate Nitrogen (N3C) Vacancies for Exceptional NOx Abatement in Visible Light

Over the past several decades, much effort has been applied to atmospheric nitrogen oxide (NOx) abatement. The current techniques require high energy consumption and result in secondary pollution. Particularly, the removal of low dose (<200 ppm) of NOx has been very challenging. Though graphitic carbon nitride (g-CN), an eco-friendly and sustainable material was tried as a promising metal-free photocatalyst for NOx abatement. Herein, a one-step, energy efficient calcination approach is developed to prepare amorphous carbon nitride (ACN) with N3(C)-site vacancies. The visible-light responsive range is expanded and the activation barrier of N(sic)O triple bonds is sharply decreased by one order of magnitude; 0.19 eV when compared to the 2.22 eV of g-CN. These modifications allow the NOx removal efficiency of ACN to reach 57.1% which is among the highest in visible light. The unique N3(C)-site vacancies are well maintained after photocatalytic NO oxidation, which shows an exceptional structural stability. This boosts the generation of singlet oxygen (O-1(2)) and superoxide radical (O-center dot(2)-) for complete NO removal. This study sheds light on the active site design and photocatalytic performance enhancement of g-CN based materials by vacancy engineering.