An ultrafast carrier dynamics system from oxygen vacancies modified SnO2 QDs and Zn2SnO4 heterojunction for deeply photocatalytic oxidation of NO

Abstract

Deeply photocatalytic oxidation of NO-to-NO3– holds great promise for alleviating NOx pollution. The major challenge of NO photo-oxidation is the highly in-situ generated NO2 concentration, and the formation of unstable nitrate species causes desorption to release NO2. In this study, SnO2 quantum dots and oxygen vacancies co-modified Zn2SnO4 (ZSO-SnO2-OVs) were prepared by a one-step hydrothermal procedure, the NO photo-oxidation was investigated by a combination of solid experimental and theoretical support. Impressively, spectroscopic measurements indicate that fast carrier dynamics can be achieved due to the electron transfer efficiency of ZSO-SnO2-OVs reaching 99.99%, far outperforming the counterpart and previously reported photocatalysts. During NO oxidation, molecular NO/O2 and H2O are efficiently adsorbed/activated around OVs and SnO2 QDs, respectively. In-situ infrared measurements and calculated electron localized function disclose two main findings: (1) richly electrons enable NO promptly form NO– instead of toxic NO2 or NO+; (2) the generation of stable and undecomposed bidentate NO3– rather than bridging or monodentate one benefits the deep oxidation of NO via shifting reaction sites from O terminals for original ZSO to Sn ones for ZSO-SnO2-OVs. The synergistic action of SnO2 QDs and OVs positively contributes to the NO oxidation performance enhancement (60.6%, 0.1 g of sample) and high selectivity of NO to NO3– (99.2%). Results from this study advance the mechanistic understanding of NO photo-oxidation and its selectivity to NO3– over photocatalysts.