The mechanism of efficient photoreduction nitrate over anatase TiO2 in simulated sunlight

Revealing the activation mechanism of nitrate (NO3-) reduction is crucially important to design high-efficiency photocatalysts for NO3- removal. In this work, the performance of photoreduction NO3- has been thoroughly studied over different crystalline phases TiO2. Photodegradation rate of NO3- over anatase TiO2 is found to be higher than that of rutile TiO2 at simulated sunlight, which can achieve high NO3- conversion of 94% and 100% nitrogen selectivity (original concentration of 50 mg/L NO3--N) at reaction time of 4 h. With the aid of in situ Fourier Transform Infrared (FTIR) and density functional theory (DFT) calculations, the possible reaction paths of photoreduction NO3- over anatase TiO2 was verified from theory and practice sides. NO3- was adsorbed on surface Ti site to form bridging nitrate (M - O)(2)=NO model. Then, monodentate nitrite (M-O-N-O) model was the dominant intermediate in the reduction process of NO3-. This study presents a new opinion of photoreduction NO3- reaction paths.

Automated summary

Revealing the activation mechanism of nitrate reduction is crucial for designing efficient photocatalysts for nitrate removal. In this study, the performance of photocatalytic nitrate reduction was thoroughly investigated on different crystalline phases of TiO2. It was found that anatase TiO2 exhibited a higher rate of nitrate degradation than rutile TiO2 under simulated sunlight conditions. The possible reaction paths of nitrate reduction on anatase TiO2 were verified through in situ Fourier Transform Infrared (FTIR) and density functional theory (DFT) calculations. This study presents a new perspective on the reaction paths of nitrate photoreduction.