Engineering Surface N-Vacancy Defects of Ultrathin Mesoporous Carbon Nitride Nanosheets as Efficient Visible-Light-Driven Photocatalysts

Graphitic carbon nitride (GCN) has become an attractive photocatalyst for solar energy conversion, but the photocatalytic activity of GCN is still limited by the extremely fast electron-hole recombination. Herein, a defective ultrathin mesoporous graphitic carbon nitride (DUMCN) photocatalyst with high specific surface area and mesoporous structure is fabricated through a facile three-step heat-treatment strategy, which reduces the distance of bulk photogenerated carriers to the surface, resulting in efficient adsorption and diffusion of reactants and products, and exposing adequate surface active sites. Moreover, suitable N-vacancy defects are formed via high-temperature surface hydrogenation, which can extend light absorption and produce ultra-high intrinsic carrier mobility, and further increase the active sites. The photocatalytic hydrogen production rate is up to 13.63 mmol h(-1) g(-1) under visible light in the triethanolamine solution and 33.5 mu mol h(-1) g(-1) for overall water splitting, which is much higher than that of bulk graphitic carbon nitride (BCN) structures. Density functional theory (DFT) calculations further reveal the effect of surface defects on the band structure for promoting the spatial charge separation. This facile strategy may offer new insights into designing other ultrathin mesoporous semiconductor photocatalysts with high performance.

Automated summary

A defective ultrathin mesoporous graphitic carbon nitride photocatalyst was synthesized with high catalytic performance, which was achieved through reducing the distance between photogenerated carriers and the surface, forming suitable N-vacancy defects, extending light absorption, and exposing adequate surface active sites.