All-solid-state MoS2/WO3 photoelectrodes as high-efficiency catalysts for reductive/sorptive/recycling of hexavalent chromium.

Photoelectrocatalysis (PEC) is an effective approach to eliminate carcinogen hexavalent chromium (Cr(VI)) in wastewater, in which high-performance catalysts are crucial. Herein, controlled growth of thin molybdenum disulphide (MoS 2) nanosheets on self-supported tungsten trioxide (WO 3) created an all-solid-state MoS 2 /WO 3 heterojunction serving as electrode and catalyst simultaneously for removing Cr(VI). Countless small and thin MoS 2 nanoflakes build in a huge and porous interface for harvesting lights and adsorbing chromium species. And the highly conductive WO 3 substrate facilitates the transfer of those photoexcited-electron and therefore suppresses the recombination between electrons and holes. Furthermore, assisted by bias potential, electron streams from external circuit render an electron-rich interface at the MoS 2 /WO 3 cathode, accelerating the Cr(VI) reduction by PEC. At −1.2 V, the PEC reduction efficiency of Cr(VI) reaches 100% within 30 min, surpassing the pristine WO 3 by 2.7 times. The generated Cr(III) ions can be immobilized on the porous MoS 2 /WO 3 cathode through electrostatic attraction, enabling removal of total chromium. More importantly, the Cr(III) anchored to the catalyst can be effortlessly recovered by eluting with clean water, which also refreshes the MoS 2 /WO 3 cathode. This study provides a new approach to fabricating photoelectrodes for sustainable PEC reduction and treatment of Cr(VI) containing wastewater. [ABSTRACT FROM AUTHOR]