Single-atom V-N charge-transfer bridge on ultrathin carbon nitride for efficient photocatalytic H2 production and formaldehyde oxidation under visible light

Solar-driven hydrogen evolution and formaldehyde oxidation are highly appealing, but insufficient active sites and restricted charge transfer channel resulted in limited photocatalytic efficiency for most reaction systems. Herein, we designed coordinating single-atomic-site V on ultrathin carbon nitride (namely, SAVCN) with V-N charge-transfer bridge as the reaction switch for photocatalytic H2 production and formaldehyde oxidation under visible light. The formation of V single-atoms was certified by spherical aberration-corrected HAADF-STEM, EXAFS, and DFT study. The electronic structure of the V-N bridge enables a stable photocatalytic hydrogen evolution activity, which is nearly 3 times above that of pristine carbon nitride under 420 nm, and further elevates the green light driven H2 generation by over 11-fold. Remarkably, the SAVCN system exhibits comparably high photocatalytic activity for gaseous formaldehyde oxidation, which is superior to most reported carbon nitride-based photocatalysts. The photocatalytic mechanistic prediction confirms that the introduced unsaturated V-N coordination favorably reduces the activation energy barrier of the hydrogen evolution, and enhances the rate-determining step of intermediates for mineralization of gaseous formaldehyde.