Enhanced photocatalytic activity and photoinduced stability of Ag-based photocatalysts: The synergistic action of amorphous-Ti(IV) and Fe(III) cocatalysts

摘要

In recent years, Ag-based materials have attracted a great deal of attentions due to their excellent photocatalytic performance. However, the rapid recombination of photogenerated charges and the poor photostability cause an obvious decrease of their photocatalytic performance. In this study, amorphous Ti(IV) as a hole cocatalyst was first successfully loaded on the surface of AgBr photocatalyst by a facile impregnation method. It was found that the photocatalytic activity of AgBr could be greatly improved by a factor of 1.5 when the loading amount of Ti(IV) cocatalyst was 0.05 wt%. Moreover, in addition to the AgBr, the amorphous Ti(IV) could also be used as an effective hole cocatalyst to greatly improve the photocatalytic performance of other Ag-based materials (such as AgCl, AgI, Ag2O, Ag2CO3, and Ag3PO4). However, owing to the rapid transfer of photogenerated holes by Ti(IV) cocatalyst, more photogenerated electrons were accumulated on the conduction band of AgBr, causing an obvious deactivation due to the reduction of surface lattice Ag+ ions to metallic Ag. In this case, after the further surface modification by Fe(III) as an electron cocatalyst, the photoinduced stability and photocatalytic activity of Ti(IV)/AgBr could be significantly enhanced. The possible reason is due to the synergistic action of amorphous Ti(IV) and Fe(III) cocatalysts, namely, Ti(IV) cocatalyst acts as a hole-capture center to efficiently transfer holes to oxidize organic contaminants, while Fe(III) cocatalyst functions as a reduction active site to reduce oxygen efficiently. Compared with the expensive noble metal cocatalyst (such as Au, Pt, and RuO2), the surface modification by low-cost transition metal cocatalysts (such as Ti and Fe) is a significant method to develop highly efficient photocatalytic materials. (C) 2016 Elsevier B.V. All rights reserved.