Rational design of CeO2/Bi7O9I3flower-like nanosphere with Z-scheme heterojunction and oxygen vacancy for enhancing photocatalytic activity

For purifying pollutants in photocatalytic reactions, promoting electron migration and preserving photogenerated charge-carrier with high redox ability are of significance. Here, flower-like nanosphere of CeO2/Bi7O9I3 with Z-scheme heterojunction and oxygen vacancy was designed and synthesized to apply to photocatalytic oxidation of heavy metal pollutant Hg0. The experimental results manifested that CB-20 (moral ratio Ce/Bi = 2:10) exhibited more excellent photocatalytic performance for Hg0 removal than that of pure CeO2 and Bi7O9I3, and Hg0 removal efficiency of CB-20 can reach up to 97.63% in simulated flue gas. Moreover, the characterization results proved presence of abundant oxygen vacancies on CB-20, which can act as electron traps to accelerate electron transfer. And combining with results of DFT calculation, ESR analysis and reactive active species trapping experiments, a built-in electric field between CeO2 and Bi7O9I3 was confirmed, and photogenerated electrons transfer along Z-scheme path, which indicated Z-scheme heterojunction was formed between CeO2 and Bi7O9I3. Finally, we proposed the dual effect of Z-scheme heterojunction and oxygen vacancy can promote electron transport and retain generated charge-carrier with high redox ability, and analyzed the photocatalytic reaction mechanism.