Harnessing defects in Ag/CeO2 for enhanced photocatalytic degradation of antibiotic in water: Structural characteristics, in-depth insights on mechanism, degradation pathway

Abstract

A highly efficient and stable CeO₂-based material has been developed for photocatalytic degradation of antibiotics in water. In this study, we investigated the defects due to metal-support interaction between Ag and CeO₂ in the Ag/CeO₂ nanocomposites. Here we introduced oxygen vacancies in CeO₂ by incorporating Ag on the surface of CeO_2. Notably, the addition of Ag to CeO₂ reduces the band gap energy to 2.90 eV, accompanied by an increase in Ce³⁺ content which is correlated with an increase in oxygen vacancies. X-ray photoelectron spectroscopy (XPS), Raman and EPR studies substantiated the increase in surface oxygen vacancies in CeO₂ induced by the interaction between Ag and CeO₂. Oxygen vacancies in Ag/CeO₂ act as trapping sites for photogenerated electrons and successfully restrain the recombination of photogenerated electron and hole pairs, thereby exhibiting improved catalytic activity of Ag/CeO₂ nanocomposites. Ag/CeO₂ nanocomposites exhibited better catalytic performance than pristine CeO₂, which is attributed to the enhanced oxygen vacancies in the nanocomposites. We investigated the effect of silver (Ag) on increasing oxygen vacancies in Ag/CeO₂.Trapping experiments were conducted to identify the reactive species participating in the photocatalytic degradation process. A plausible mechanism is proposed based on critical analysis of the results from the characterization techniques of the nanocomposites and photocatalytic experiments. The possible degradation pathways for Ciprofloxacin along with the degradation intermediates have been proposed based on High resolution mass spectroscopy (HRMS) analysis. This study provides insights on structural characteristics of defective CeO₂, in-depth photocatalytic mechanism and degradation pathway of ciprofloxacin, that could facilitate the exploration of other ceria-based nanocomposites for catalytic applications.