Using Er/Cd-Codoped BiOBr Microspheres to Enhance Antibiotic Degradation under Visible Illumination: A Combined Experimental and DFT Investigation.

High levels of antibiotic accumulation and the difficulty of degradation can have serious consequences for the environment and, therefore, require urgent attention. To solve this problem, a synergistic Er and Cd ion-codoped BiOBr photocatalyst was proposed. The degradation rate of sulfamethoxazole (SMX) by Er/Cd-BiOBr was eight times higher than that of pure BiOBr, exceeding that of single Er-doped or Cd-doped BiOBr, which was attributed to the ability of Er/Cd-BiOBr to generate a variety of free radicals. Experimental results and theoretical calculations suggested a possible mechanism for the improved photocatalytic degradation rate. The reduction of the band gap can facilitate the production of electron-hole pairs, which play a significant role in the production of reactive radicals. Furthermore, an optimal stabilized structure of the ErCd-BiOBr dopant system was identified based on the formation energy formulas of different ligand configurations. These findings offer promising potential for the degradation of broad-spectrum antibiotics and provide valuable insights for the design and modification of photocatalytic materials.