Oxygen vacancy defects-boosted deep oxidation of NO by β-Bi2O3/CeO2-δp-n heterojunction photocatalyst in situ synthesized from Bi/Ce(CO3)(OH) precursor

Abstract

Flower-like n-type CeO2-δ is hybridized with p-type β-Bi2O3 nanoparticles to design a novel β-Bi2O3/CeO2-δp-n heterojunction photocatalyst via a thermal treatment process of Bi/Ce(CO3)(OH) precursor. The synthesized β-Bi2O3/CeO2-δ exhibits a remarkable enhancement in NO removal and significant suppression of toxic intermediates nitrogen dioxide (NO2) under visible light irradiation. The superior photocatalytic activity of β-Bi2O3/CeO2-δ for NO removal is mainly derived from the synergistic effects of the oxygen vacancies (OVs) and p-n heterojunction. The OVs not only enhance the visible light utilization and boost the separation of electron-hole pairs but also improve the adsorption and activation of NO and O2. Particularly, the p-n heterojunction is beneficial for the interfacial migration of photogenerated charge carriers. Electron spin resonance (ESR) and trapping experiment reveal that the synergistic effects of OVs and p-n heterojunction can induce the generation of more active species. The electrochemical measurements and density-functional theory (DFT) calculations in-depth confirm that both p-n heterojunction and OVs can accelerate the interfacial charge transfer, resulting in the deep oxidation of reactants. Therefore, the flower-like β-Bi2O3/CeO2-δp-n heterojunction photocatalyst exhibits an advanced photocatalytic activity for deep NO removal and a suppressed NO2 generation. In addition, monitoring the reaction products by in situ Fourier transform infrared spectrum (FTIR) further validates that the main products of nitrates are formed during the photocatalytic process. This work demonstrates a straightforward approach for construction of p-n heterojunction photocatalysts, which can enhance the effective photocatalytic activity and stability for NO removal.