BiOI-SnO(2) Heterojunction Design to Boost Visible-Light-Driven Photocatalytic NO Purification

The efficient, stable, and selective photocatalytic conversion of nitric oxide (NO) into harmless products such as nitrate (NO(3)(−)) is greatly desired but remains an enormous challenge. In this work, a series of BiOI/SnO(2) heterojunctions (denoted as X%B-S, where X% is the mass portion of BiOI compared with the mass of SnO(2)) were synthesized for the efficient transformation of NO into harmless NO(3)(−). The best performance was achieved by the 30%B-S catalyst, whose NO removal efficiency was 96.3% and 47.2% higher than that of 15%B-S and 75%B-S, respectively. Moreover, 30%B-S also exhibited good stability and recyclability. This enhanced performance was mainly caused by the heterojunction structure, which facilitated charge transport and electron-hole separation. Under visible light irradiation, the electrons gathered in SnO(2) transformed O(2) to ·O(2)(−) and ·OH, while the holes generated in BiOI oxidized H(2)O to produce ·OH. The abundantly generated ·OH, ·O(2)(−), and (1)O(2) species effectively converted NO to NO(−) and NO(2)(−), thus promoting the oxidation of NO to NO(3)(−). Overall, the heterojunction formation between p-type BiOI and n-type SnO(2) significantly reduced the recombination of photo-induced electron-hole pairs and promoted the photocatalytic activity. This work reveals the critical role of heterojunctions during photocatalytic degradation and provides some insight into NO removal.