Sol–gel auto-combustion synthesis of a novel ternary magnetic-recyclable ZnFe2O4/ZnO/CeO2 nano-photocatalyst for highly efficient visible-light-induced degradation of organic contaminants

Abstract

The creation and design of highly efficient photocatalysts responsive to visible light are critically required to address pressing environmental challenges. The present work focuses on the design and controlled synthesis of a novel magnetically separable ternary nano-photocatalyst comprising ZnFe₂O₄, ZnO, and CeO₂ through a facile one-step sol–gel auto-combustion method. This ternary photocatalyst integrates the magnetic characteristics of ZnFe₂O₄, the durability and catalytic efficiency of ZnO, along with the oxygen storage capabilities and photocatalytic features of CeO₂. Besides, the sol–gel auto-combustion process serves as a self-sustaining technique for generating heat through its exothermic reactions, providing several advantageous characteristics such as uniformity, reduced particle size, improved distribution, and controlled morphology. The effects of different fuel agents on the phase purity and crystallite dimensions of ZnFe₂O₄/ZnO/CeO₂ were assessed. According to the FESEM images, the sample synthesized using oxalic acid as fuel revealed a porous structure with a particle size distribution near 18.97 nm, making it an outstanding choice for photocatalytic performance. The study revealed that the ZnFe₂O₄/ZnO/CeO₂ photocatalysts exhibited exceptional catalytic performance under neutral conditions, providing a significant advantage in photocatalytic activity. The photoactive properties of the ternary nanocomposite were tested by measuring the degradation of Erythrosine (ER) and Methyl Violet (MV) under visible light conditions. The findings revealed that the anionic dye is broken down significantly more effectively than the cationic dye. The photocatalyst exhibited impressive photocatalytic capabilities, achieving a degradation efficiency of 92.33% for ER. The combination of ZnFe₂O₄, ZnO, and CeO₂ enhances photocatalytic performance because of their synergistic features, substantial surface area, increased active sites, optimized charge dynamics, and potential for reuse. Notably, scavenger analysis revealed that hydroxyl radicals were significantly present in the ZnFe₂O₄/ZnO/CeO₂ sample when exposed to visible light, functioning as the main oxygen-derived radicals in breaking down pollutants through photocatalysis. Furthermore, insights into the photocatalytic reaction mechanism and the •OH generation process on the ternary photocatalyst were provided. The study comprehensively examined reaction kinetics, the durability of catalysts, and the impact of different variables like initial concentration of the dye solution and photocatalyst dosage during photocatalytic activity. Research results suggest that the pseudo-first-order kinetic model best describes the adsorption behavior of dyes on photocatalysts.