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

Abstract

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 NOx 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 O2 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 μA 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.