Harnessing defects in Ag/CeO2 for enhanced photocatalytic degradation of antibiotic in water: Structural characteristics, in-depth insights on mechanism, degradation pathway
Ajit Kumar Dhanka, Emerson C. Kohlrausch, Raghabendra Samantray, Vinod Kumar, Balaram Pani, Nityananda Agasti
Abstract
• Efficient degradation of ciprofloxacin in water by Ag/CeO 2 nanocomposites. • Detailed mechanism and degradation pathway of ciprofloxacin. • Metal support interaction between Ag and CeO 2 increases oxygen vacancies in CeO 2 • Oxygen Vacancies in CeO 2 act as trapping sites for photogenerated electrons and thereby restrains the recombination of e - and h + pair. • In-depth characterization and analysis of oxygen vacancies in CeO 2 • Mechanistic details of photocatalysis with crucial role of defects in CeO 2 A highly efficient and stable CeO 2 -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 CeO 2 in the Ag/CeO 2 nanocomposites. Here we introduced oxygen vacancies in CeO 2 by incorporating Ag on the surface of CeO 2. Notably, the addition of Ag to CeO 2 reduces the band gap energy to 2.90 eV, accompanied by an increase in Ce +3 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 CeO 2 induced by the interaction between Ag and CeO 2 . Oxygen vacancies in Ag/CeO 2 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/CeO 2 nanocomposites. Ag/CeO 2 nanocomposites exhibited better catalytic performance than pristine CeO 2 , which is attributed to the enhanced oxygen vacancies in the nanocomposites. We investigated the effect of silver (Ag) on increasing oxygen vacancies in Ag/CeO 2 .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 CeO 2 , in-depth photocatalytic mechanism and degradation pathway of ciprofloxacin, that could facilitate the exploration of other ceria-based nanocomposites for catalytic applications.