The mechanism of catalytic degradation of secnidazole by semiconductor titanium dioxide: A density functional theory study

Abstract

Photocatalytic degradation of nitroimidazole antibiotics is a very promising method. In this work, we not only employed density functional theory (DFT) calculations to investigate the degradation mechanism of secnidazole on the surfaces of anatase TiO2 (101) and (001) but also explored the structural changes of secnidazole in the course of the degradation process. Specifically, we first optimized the adsorption configurations of secnidazole on different surfaces and analyzed the optimal adsorption sites, adsorption energies, and the most stable adsorption configurations. We found that secnidazole was adsorbed on the TiO2 surfaces via hydrogen bonds. Meanwhile the CN bond on the imidazole ring is weakened during the adsorption process, which facilitates the ring-opening reaction of the imidazole. Finally, we investigated two possible degradation pathways of secnidazole on different TiO2 surfaces and obtained their reaction mechanisms, based on which we concluded that the degradation of secnidazole is more likely to take place on the (101) surface of anatase TiO2.