Facile room-temperature precipitation strategy for Ag2O/Bi2WO6 heterojunction with high simulated sunlight photocatalytic performance via bi-directed electron migration mechanism

摘要

A trace Ag2O modified Bi2WO6 heterojunction was facilely synthesized via a solution precipitation strategy at ambient temperature. The characterizations of composition, morphology, microstructure, UV-vis absorption, photoluminescence, BET, photocurrent and solar simulated photocatalytic behavior were systematically investigated. They showed that besides a few visible nanoparticles, most of the Ag2O phase was inconspicuously distributed on the surface of the Bi2WO6 substrate. The composite photocatalyst exhibited obviously enhanced photocatalytic activity compared with pure Ag2O and Bi2WO6 for degradation of organic contaminants. In particular, the sample of Ag-0.6 wt% presented the best photocatalytic activity with a rate constant 4.8-fold as fast as that of Bi2WO6. Photochemical and photoelectrochemical analysis indicated that the introduction of trace Ag2O effectively broadened the visible-light absorption and inhibited the photogenerated carrier recombination in Bi2WO6. Based on band structure analysis and XPS results of recycled samples, a bi-directed migration mechanism of photogenerated electrons is proposed at the heterostructure interface. The band-gap coupling effect between Ag2O and Bi2WO6 and the electronic effect of trace metallic Ag in situ photoreduced from the self-stabilized Ag2O are believed to play vital roles in the separation and migration of e(-)/h(+) pairs. The work provides some insights into the rational design of hybrid photocatalysts with high performance via multi-path photogenerated carrier migration.