Synergistic silver doping and N vacancy promoting photocatalytic performances of carbon nitride for pollutant oxidation and hydrogen production
Yifan Kong, Degang Li, Chengxu Zhang, Wenyuan Han, Yan Xue, Weimin Zhang, Hongqi Sun, Shaobin Wang, Xiaoguang Duan
Abstract
Carbon nitride (C3N4) has attracted immense interest as a low-cost, non-toxic and naturally abundant raw material. However, graphite-like phase carbon nitride (g-C3N4) still suffers from poor visible light absorption, fast charge carrier recombination, slow electron mobility and relatively fewer surface-active sites. In this work, we synthesized silver-doped N vacancy-rich carbon nitride (AgCN) with convoluted ultra-thin lamellar layers from Ag precursors and melamine-cyanuric acid monomers using a self-assembly supramolecular strategy. AgCN exhibited excellent photocatalytic performance and stability. The introduction of N vacancies disrupted the off-domain π-bonds and weakened the conjugation effect of the triazine ring elements. The large specific surface area of the convoluted ultra-thin lamellar structure helps suppress the aggregation of active silver centers, and the Ag-N2C2 bond acts as a bridge for photoexcited charge transfer to promote the separation and transfer of photogenerated electron/hole pairs for surface redox reactions. As a result, AgCN exhibited excellent photocatalytic performance for photodegradation of rhodamine B (RhB) and hydrogen production (1.69 mmol g-1h−1), well outperforming the pristine CN. Density flooding theory (DFT) calculations revealed the improved conductivity and efficient separation of electron-hole pairs in AgCN at the excited state, generating superoxide radicals, singlet oxygen and holes.