Adsorption characteristics and degradation mechanism of metronidazole on the surface of photocatalyst TiO2: A theoretical study

In this paper, the adsorption and degradation mechanism of metronidazole on TiO₂ (101) and (001) surfaces was elucidated at DFT level. The adsorption stability of metronidazole on the surface of anatase was studied under the condition of vacuum and neutral aqueous solvent respectively, and the most stable adsorption configuration was optimized theoretically. It was found that metronidazole could be adsorbed on the surface of TiO₂ under both conditions. The hydrogen bond generated by the adsorption process can enhance the stability of the adsorption structure. The surface adsorption made the CN bond length of metronidazole longer, which could facilitate the reaction of open-loop degradation. The mechanism of ring-opening degradation of metronidazole on two surfaces of TiO₂ was also studied. It was found that the activation energy of the degradation reaction of metronidazole on the crystal plane of TiO₂ was decreased under the condition of water solvent, which indicated that the solvent condition could promote the degradation of metronidazole. The utilization efficiency of different crystal planes of TiO₂ in the visible light and predicted the photocatalysis were achieved. The study found that TiO₂ (101) crystal plane catalytic degradation of metronidazole has high visible light utilization rate, explaining the experimental results.