Defect-enriched CuO/CeO2 nanostructure: in-depth structural characterization and photocatalytic performance

Abstract

The catalytic activity of CeO₂ can be modulated by incorporating defects and inducing strong metal–support interactions. Herein, we introduce CuO into CeO₂ for generating oxygen vacancies (CeO_2−x) via the interaction between CuO and CeO₂. The resultant catalyst CuO/CeO₂ exhibited improved performance for the photocatalytic degradation of isoproturon (a herbicide). The improvement in catalytic performance was attributed to the oxygen vacancies and interfacial charge transfer between CuO and CeO₂. Notably, the addition of CuO increased the oxygen vacancies in CeO₂, correlating with the increase in the Ce³⁺ content (31.2%). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy studies substantiated the increase in surface oxygen vacancies in CeO₂. We investigated the oxygen vacancies quantitatively and detected the chemical states of the Cu and Ce species. Photoluminescence (PL) studies validated the role of oxygen vacancies in restraining the recombination of photogenerated electron and hole pairs, thereby improving the catalytic activity of CuO/CeO₂. Trapping experiments were conducted to identify the reactive species involved in the photocatalytic degradation process. Based on a thorough evaluation of the characteristics of the catalyst and photocatalysis experimental outcomes, a potential reaction mechanism was proposed. Furthermore, high-resolution mass spectrometry (HRMS) analysis was utilized to identify degradation intermediates, enabling us to outline the possible degradation pathways of isoproturon. Isoproturon (IPU) was effectively degraded under UV light with CuO/CeO₂ compared with pristine CeO₂. A 95% degradation efficiency was achieved with CuO/CeO₂ (10 mg) for the IPU solution (10 μg L⁻¹) within 120 minutes. This study provides detailed insights into the structural analysis of defective CeO₂ and an in-depth mechanism of its photocatalysis, facilitating the design of high-performance ceria-based catalysts for photocatalytic degradation of emerging contaminants in water.