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

Abstract

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.