Synthesis and photocatalytic activity of cation-doped titanium oxynitrides (Ti_2.85-MO₄N, M = Zn, Co, Cu)

The utilization of visible light in photocatalytic semiconductors is restricted by the presence of a wide energy bandgap and fast electron-hole pair recombination. This study aims to address this limitation by synthesizing nitrogen- and cation-doped Cs_0.68Ti_1.83O₄ at varying temperatures and subsequently analyzing the photocatalytic performance and mechanism. The optical experimental findings indicate that the co-doping of N/M (where M represents Zn, Co, or Cu) can considerably decrease the energy bandgap of Cs_0.68Ti_1.83O₄ by regulating the energy band position and effectively suppressing the recombination of photogenerated carriers. Notably, at a temperature of 600 °C, the N/Cu co-doped Cs_0.68Ti_1.83O₄ exhibits the smallest energy bandgap of 1.98 eV, thereby demonstrating superior photocatalytic performance. The photocatalytic degradation test of pollutants shows that the degradation efficiency of methylene blue solution in 120 minutes under light was 84%, which is the result of the interaction between ˙OH and ˙O₂^-. This study provides new possibilities for the study of co-doped modified photocatalytic materials.