Enhanced Visible-Light Photocatalytic Activity of Ag QDs Anchored on CeO₂ Nanosheets with a Carbon Coating

Ag quantum dots (QDs) anchored on CeO2 nanosheets with a carbon coating (Ag/CeO2@C) (composites) were prepared via an in situ reduction approach for the photocatalytic degradation of Cr(VI) and tetracycline hydrochloride (TCH) in the visible-light region. The photocatalytic activity of Ag/CeO2@C was greatly affected by carbon content, Ag-doping content, Cr(VI) concentration, pH value, and inorganic ions. Enhanced photocatalytic activity was obtained by Ag/CeO2@C (compared to CeO2 and CeO2@C), of which 3-Ag/CeO2@C-2 with an Ag-doping content of 5.41% presented the best removal efficiency and the most superior stability after five cycles. ·O2− and ·OH radicals were crucial for the photocatalytic capacity of 3-Ag/CeO2@C-2. The combined effect of the surface plasma resonance (SPR) of Ag QDs, an electron trapper of carbon shells, and the redox activity of the Ce(III)/Ce(IV) coupling induced efficient charge transfer and separation, suppressing the recombination of electron−hole pairs.