Synergistic silver doping and N vacancy promoting photocatalytic performances of carbon nitride for pollutant oxidation and hydrogen production

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.