Deep NO oxidation in Zn2SnO4 by dual-anionic-defects engineering

Abstract

Zinc stannate (ZTO) photocatalysts are considered to hold potential advantages towards air pollution control. However, the interaction between the limited surface reaction sites of the as-reported ZTO system and the target pollutant molecules tends to be too weak to achieve the decent adsorption and activation. Whilst reactive sites can be occupied by intermediate toxic by-products in the photocatalytic removal process to result in the loss of photoactivity. Herein, we designed and synthesized dual anion defect sites, i.e., oxygen vacancies (OVs) and interstitial Br- doping decorated ZTO (BZTO) by a one-step hydrothermal method. Through the structural characterization of XPS, EPR and a series of photoelectrochemical measurements, we confirmed that the successfully introduced dual anion defect sites can effectively promote the light absorption of the BZTO, improve the efficiency of carrier separation and transport, and thus increase the number of active free radicals. Moreover, we also adopted the deep combination of in situ DRIFTS and DFT calculation. It was found that the NO adsorption sites were changed from O terminals for bare ZTO to Zn ones, which favorably reduces the conversion potential barrier of intermediate NO2, and greatly improves its NO removal rate, up to 62%. This study provides a new surface modification strategy and insight as well an effective solution for photocatalytic removal of gaseous pollutants.