Effects of H2O2 generation over visible light-responsive Bi/Bi2O2-xCO3 nanosheets on their photocatalytic NOx removal performance

The photocatalytic removal of gaseous NOx is commonly accompanied by secondary pollution, which necessitates the development of highly efficient nanostructured catalysts with a decreased propensity to toxic intermediate production. Herein, we describe the synthesis of plasmonic Bi/Bi2O2-xCO3 and demonstrate the presence of surface oxygen vacancies therein, revealing that the maximal NO, removal efficiency of Bi/Bi2O2-xCO3 under visible light irradiation reached 50.5% and exceeded that of a commercial photocatalyst, while the production of toxic NO2 as a by-product was completely suppressed (the selectivity reached up to 98%). In-situ introduction of plasmonic Bi on the surface of Bi2O2-xCO3 promoted the generation of H2O2 by capturing electrons from the defect states of Bi2O2-xCO3 via the two-electron reduction of O-2 and thus inhibited NO2 production (as confirmed by scavenger experiments), additionally broadening the light absorption range of the above photocatalyst. Moreover, surface oxygen vacancies in Bi-O layers provided a channel for electron transfer between Bi and Bi2O2-xCO3, which resulted in increased charge separation efficiency (maximum photocurrent = 1.1 Mu A cm(-2), 14.5 times higher than that of pristine Bi2O2CO3). Furthermore, the toxicity assessment authenticated good biocompatibility of Bi/Bi2O2-xCO3. Thus, this study sheds light on the possible roles of H2O2 in NOx degradation and provides an efficient surface engineering strategy to prepare highly reactive and selective photocatalysts.