High-ratio {100} plane-exposed ZnO nanosheets with dual-active centers for simultaneous photocatalytic Cr(VI) reduction and Cr(III) adsorption from water.

Abstract

The development of an efficient catalyst for the simultaneous removal of Cr(VI) and Cr(III) from water is required to eliminate the risk of Cr(III) reconversion in the photocatalytic Cr(VI) reduction process. ZnO with large regions of high-energy {001} and {101} surfaces is often used to degrade various pollutants due to its high activity. However, the more readily available low-energy facets have relatively limited its applications. Here, we report a new strategy that employs a high proportion of {100} plane-exposed ZnO nanosheets for simultaneous photocatalytic Cr(VI) reduction and Cr(III) adsorption. The mechanism of Zn-O co-exposed on the {100} plane as the dual-active centers to jointly promote Cr(VI) reduction and Cr(III) adsorption was clarified at the atomic level. ZnO nanosheets with a high exposure ratio of the {100} plane achieve a total Cr removal rate of over 90% within 120min under simulated sunlight irradiation, neutral conditions, and a negligible difference in the band structure.