Efficient charge separation of a Z-scheme Bi5O7−δI/CeO2−δ heterojunction with enhanced visible light photocatalytic activity for NO removal

Abstract

In this work, a novel Z-scheme Bi₅O_7−δI/CeO_2−δ heterojunction photocatalyst was prepared by combining hydrothermal synthesis and thermal treatment methods. Oxygen vacancies were in situ generated on the surface of Bi₅O_7−δI and CeO_2−δ nanostructures. The existence of oxygen vacancies significantly improved the light absorption of CeO_2−δ and inhibited the recombination of photogenerated carriers. Based on the photocatalytic activity, the as-prepared Bi₅O_7−δI/CeO_2−δ photocatalyst exhibited excellent photocatalytic NO removal performance under visible light irradiation. The results of the capture experiment and electron spin resonance (ESR) spectroscopy show that super oxygen radicals (˙O₂⁻) and hydroxyl radicals (˙OH) are the main active species in the overall photocatalytic reaction process. Density functional theory (DFT) calculations and ESR results demonstrate that a Z-scheme heterojunction is formed between Bi₅O_7−δI and CeO_2−δ. Compared with the traditional type-II heterojunction, the Z-scheme heterojunction exhibited more efficient charge separation and robust redox capacity in the photocatalytic reaction.