Enhanced visible-light photocatalytic degradation efficiency of Ce3+-doped ZnO nanoparticles synthesized by sol-gel method

While Ce3+-doped ZnO nanoparticles have been extensively explored for UV light photocatalytic applications, harnessing their efficacy for visible light photocatalysis remains a significant challenge. This study demonstrates the outstanding degradation efficiency under visible light of Ce3+-doped ZnO nanoparticles synthesized via the sol-gel route. At lower concentrations (<3 mol%), Ce3+ ions seamlessly substitute Zn2+ ions within the ZnO lattice, while at higher dopant levels (≥3 mol%), the formation of CeO2 nanoparticles on the ZnO surface becomes an additional noteworthy feature. This unique combination in highly Ce3+-doped ZnO nanoparticles leads to the creation of Ce-impurity states (e.g., Ce3+/Ce4+) within the ZnO structure, effectively separating electrons and holes. Consequently, the generation of superoxide radical anions is enhanced, boosting the remarkablely DB71 dye degradation efficiency (>90%) of all highly Ce3+-doped ZnO samples (≥3 mol%) in comparison with pristine and lightly Ce3+-doped ZnO samples (<3 mol%). In all highly Ce3+-doped ZnO samples, 5-mol% doped sample shows the highest DB71 degradation efficiency of 98.4%. This remarkable achievement is observed when utilizing 0.1 g of 5-mol% doped sample, 50 mg/L of initial DB71 concentration, pH of 5, and notablely under visible light irradiation. Furthermore, the DB71 degrading efficiency of ZnO:5%Ce3+ maintains an impressive 90.3% over five cycles from its initial value of 98.4%, underscoring the potential of ZnO:Ce3+ as a promising photocatalyst for practical wastewater treatment.