Preparation of core-shell structure Ag@TiO2 plasma photocatalysts and reduction of Cr(VI): Size dependent and LSPR effect

The poor light absorption and low carrier separation efficiency of Titanium dioxide (TiO 2 ) limit its further application. The introduction of plasma metal Ag have the potential to solve these drawbacks owing to its plasma resonance effect. Thus core-shell structure Ag@TiO 2 plasma photocatalysts was prepared by using facile reduction method in this work. More specifically, Ag@TiO 2 composite catalysts with different Ag loading amounts were prepared in the presence of surfactant PVP. Ag@TiO 2 demonstrates excellent light absorption performance and photoelectric separation efficiency compared with pure TiO 2 . As a result, it displays excellent performance of Cr(VI) reduction under visible light. The optimal composite catalysts Ag@TiO 2 –5P achieves exceptional visible-light-driven photocatalytic Cr(VI) reduction efficiency of 0.01416 min −1 that is 2.29 times greater than pure TiO 2 . To investigate the role of PVP, we also synthesized Ag@TiO 2 -5 without PVP. The experimental results show that although Ag@TiO 2 -5 Cr(VI) reduction performance is superior to pure TiO 2 , it significantly decreases compared with Ag@TiO 2 –5P. The results of TEM and optoelectronic testing show that agglomeration of Ag particles leads to a decrease in the photoelectric separation efficiency of Ag@TiO 2 -5. The smaller Ag particles provide more active sites and demonstrating a stronger overall local surface plasmon resonance (LSPR) effect. DMPO spin-trapping ESR spectra testing indicates that ∙O 2 − and ∙OH are the main reactive species. This research provides a potential strategy to prepare Ag-based plasma photocatalysts for environment protection.