Boosting Photocatalytic Performance of ZnO via Ce-Induced d-Band Modulation: Synthesis and Rhodamine B Degradation

Synthetic dyes are persistent organic pollutants in aquatic environments, posing serious ecological and health risks. Here, we report a morphology-guided and interface-engineered ZnO-based photocatalyst for efficient dye degradation. Among morphology-controlled ZnO architectures, sphere-like ZnO exhibited superior activity owing to favorable structural and surface characteristics. Subsequent deposition of CeO₂ formed a CeO₂/ZnO heterojunction, in which mixed-valence Ce³⁺/Ce⁴⁺ species promoted interfacial charge redistribution and reactive oxygen species generation, leading to an enhancement exceeding 50% in degradation kinetics compared with pristine ZnO. Density functional theory calculations revealed that interfacial electron transfer induces an upward shift of the Zn d-band center, facilitating oxygen activation. The catalytic performance was further optimized under representative reaction conditions, and a magnetically separable CeO₂/ZnO-ZnFe₂O₄ composite was constructed to enable efficient catalyst recovery and long-term stability. This work demonstrates how morphology control and heterojunction design cooperatively regulate electronic structure and photocatalytic reactivity in oxide-based systems for environmental remediation.