The enhanced photocatalytic activity of Ag-Fe2O3-TiO2 performed in Z-scheme route associated with localized surface plasmon resonance effect

Abstract

A Z-scheme mechanism associated with localized surface plasmon resonance (LSPR) effect is proposed and proved in a ternary Ag-Fe2O3-TiO2 composite for photocatalytic reactions. The Ag, Fe2O3 and TiO2 nanoparticles are prepared to exist in a closely connected Ag-Fe2O3-TiO2 heterostructure. Compared to TiO2, the addition of Ag-Fe2O3 causes a broad absorption in visible region by LSPR effect of Ag to facilitate electron transfer from TiO2 to Ag. In addition, electron migration from TiO2 to Fe2O3 can also be detected, indicating the interface between TiO2 and Fe2O3 can offer a route with low resistance for charge separation and directional transfer. As a result, photocatalytic activities are greatly improved in Ag-Fe2O3-TiO2, with the highest calculated apparent kinetic constant located at 0.027 min−1, which is 7.3, 1.9, 1.7 and 1.5 times of Ag-Fe2O3, TiO2, Ag-TiO2 and Fe2O3-TiO2, respectively. Free radical quenching experiments show that O2-∙ and positively charged holes are main oxidative species responsible for the degradation of dyes. Specifically, OH∙ radicals can be hardly found in pure TiO2 under irradiation but can be extensively produced and participate in the degradation after the addition of Ag-Fe2O3, which further proves that a Z-scheme route dominates the electron transfer between TiO2 and Fe2O3.