Post-illumination activity of Bi2WO6 in the dark from the photocatalytic \u201cmemory\u201d effect

Weiyi Yang,Licheng Sang,Shuang Gao,Jian Ku Shang,Caixia Sun,Qi Li,Ruoge Tao,Yan Chen

doi:10.1007/s40145-020-0448-8

Abstract

Photocatalysts with the photocatalytic “memory” effect could resolve the intrinsic activity loss of traditional photocatalysts when the light illumination is turned off. Due to the dual requirements of light absorption and energy storage/release functions, most previously reported photocatalysts with the photocatalytic “memory” effect were composite photocatalysts of two phase components, which may lose their performance due to gradually deteriorated interface conditions during their applications. In this work, a simple solvothermal process was developed to synthesize Bi2WO6 microspheres constructed by aggregated nanoflakes. The pure phase Bi2WO6 was found to possess the photocatalytic “memory” effect through the trapping and release of photogenerated electrons by the reversible chemical state change of W component in the (WO4)2− layers. When the illumination was switched off, Bi2WO6 microspheres continuously produced H2O2 in the dark as those trapped photogenerated electrons were gradually released to react with O2 through the two-electron O2 reduction process, resulting in the continuous disinfection of Escherichia coli bacteria in the dark through the photocatalytic “memory” effect. No deterioration of their cycling H2O2 production performance in the dark was observed, which verified their stable photocatalytic “memory” effect.

Highlights

Photocatalytic “memory” effect, whereby a photocatalyst could remain active for an extended period of time in the dark, is a recent development in photocatalysis [1,2,3,4]
If the concept of the “memory” effect in BWO extends to other pure phase photocatalysts with similar energy storage/release function, the selection of photocatalytic materials may be largely expanded in search for continuous activity in the dark for a broad range of environmental applications
Post-illumination activity in the dark for an extended period of time was found in pure phase Bi2WO6 microspheres from the photocatalytic “memory” effect

Summary

Introduction

Photocatalytic “memory” effect, whereby a photocatalyst could remain active for an extended period of time in the dark, is a recent development in photocatalysis [1,2,3,4]. It may be postulated that a photocatalytic “memory” effect may be found in the pure phase Bi2WO6, where its (WO4)2− layers could act to store and release charge carriers, creating a post-illumination photocatalytic activity that may extend over a long period of time (hours) Such a unique “memory” effect would be very different from that observed in the composite photocatalyst and would overcome the very short lasting problem that pure phase Se nanorods and Bi nanoparticles demonstrated. Post-illumination activity lasting for an extended period of time in the dark was observed in the pure phase Bi2WO6 microspheres from the photocatalytic “memory” effect Such a unique photocatalytic “memory” effect was found to be stable over multiple cycles, with very little loss, unlike the “memory” effect found in previously reported composite photocatalysts, where the interfacial contact deteriorates over multiple cycles of light on/off. If the concept of the “memory” effect in BWO extends to other pure phase photocatalysts with similar energy storage/release function, the selection of photocatalytic materials may be largely expanded in search for continuous activity in the dark for a broad range of environmental applications

Experimental

Results and discussion

Conclusions