Electronic and photocatalytic properties of Cu4 cluster-modified Ag/g-C3N4 single-atom catalysts: A hybrid DFT study

Abstract

Increasing the active sites on the catalyst surface has been a key goal to increase the catalyst efficiency. This paper presents an efficient conversion of solar energy into chemical energy, realized by a Cu4 cluster-assisted single-atom catalyst (Ag-doped g-C3N4). The catalyst enhances charge transfer and light absorption, and the unique advantages of this approach in the field of photocatalysis are substantiated by density functional theory. Under the synergistic effect of Cu4 clusters, the electronic state density distribution of the Ag single-atom catalyst substrate is drastically altered, which realizes the increase of substrate active sites and rapid charge separation and transfer. Compared with the pristine substrate g-C3N4, the new electronic state distribution and the generation of impurity energy levels lead to the narrowing of the band gap from 2.77 to 1.83 eV, accelerating the transfer and separation of electrons and holes, and enlarging the visible light absorption range from 410 to 760 nm, thus improving the solar energy utilization. Despite the reduced band gap, the conduction and valance band edges of (Ag, Cu4) codoped g-C3N4 still have sufficient potential to split water. Therefore, to improve the photocatalytic performance under visible light, simultaneous codoping of the Ag single atom and Cu4 cluster on g-C3N4 is an effective strategy. The study provides theoretical support for further optimization of single-atom catalysts.