Hydrazine-driven cation valence regulation and defect engineering in CeVO4 for highly efficient reduction of organic dyes and heavy metal pollutants in the dark

Abstract

Tetragonal wakefieldite (CeVO4)-like CeVOS catalysts with exceptional performance in catalytic reduction of Cr6+, MB, and RhB pollutants in the presence of NaBH4 under dark was prepared via a green and facile method. Hydrazine reduces V5+ ions to elevate the V4+ contents, and sulfur-doped is employed to balance lattice deviations from electrical neutrality induced by high V4+ concentrations, enhancing overall stability. Hydrazine modulation regulates the V4+/(V4++V5+) ratio, influencing sulfur doping, defect structure, and electron transfer efficiency. The CeVOS catalyst with an optimized V4+/(V4++V5+) ratio of 0.46 with abundant oxygen vacancies and exhibited exceptional catalytic performance. The 100 mL 50 ppm Cr6+, MB, and RhB solution were completely reduced in 10 min and durable stability, after six runs, it still achieved a 98.8% reduction of Cr6+ within 10 min. Response surface methodology (RSM) elucidated variable interactions and their influence on catalytic reduction performance. The model’s robustness is underscored by a predicted R2 of 0.9345. Optimal conditions for pollutant treatment in practical applications are 15 mg of catalyst, 25 mg of sacrificial agent, and a pH value of 6.8. Therefore, the green synthesis of efficient CeVOS catalysts bears excellent promise for industrial wastewater treatment.