Synthesis of a Bi₂O₂CO₃/ZnFe₂O₄ heterojunction with enhanced photocatalytic activity for visible light irradiation-induced NO removal

Although bismuth subcarbonate (Bi₂O₂CO₃), a member of the Aurivillius-phase oxide family, is a promising photocatalyst for the removal of gaseous NO at parts-per-billion level, the large band gap of this material restricts its applications to the UV light region. The above problem can be mitigated by heterojunction fabrication, which not only broadens the light absorbance range, but also inhibits the recombination of photogenerated charge carriers. Herein, we implement this strategy to fabricate a novel Bi₂O₂CO₃/ZnFe₂O₄ photocatalyst for NO removal under visible light irradiation and authenticate the formation of the above p-n heterojunction using an array of analytical techniques. Notably, the above composite showed activity superior to those of its individual constituents, and the underlying mechanisms of this activity enhancement were probed by density functional theory calculations and photocurrent measurements. Elevated electron/hole separation efficiency caused by the presence of an internal electric field at the Bi₂O₂CO₃/ZnFe₂O₄ interface was identified as the main reason of the increased photocatalytic activity, with the main active species were determined as [rad]O₂⁻ and [rad]OH by electron spin resonance spectroscopy. Finally, cytotoxicity testing proved the good biocompatibility of Bi₂O₂CO₃/ZnFe₂O₄. Thus, this work presents deep insights into the preparation and use of a green p-n heterojunction catalyst in various applications.