Improved electrochemical Cr(VI) detoxification by integrating the direct and indirect pathways

• An integrated direct and indirect electrochemical Cr(VI) reduction was developed.
• In-situ generated H2O2 was employed as efficient indirect reduction mediator.
• This intensification method provides new insight on the electrocatalysis.

Cr(VI) is classified as one of the 17 chemicals posing greatest threat towards humans, therefore considerable efforts have been made to reduce the Cr(VI) pollution. In this study, a novel integrated direct and indirect electrochemical Cr(VI) reduction was first reported for the highly efficient Cr(VI) detoxification. Through the controllable oxygen reduction reaction (ORR), the H2O2 was readily generated and employed as a mediator to synergistically improve the direct Cr(VI) reduction. A significant degradation enhancement was achieved from 37% to 100% within a fast 40 min treatment. Besides, there is an optimum pH condition for Cr(VI) reduction due to the competition between the mechanistic and kinetic consideration. This novel intensification approach provides new insight on the application of electrocatalysis in environmental remediation.

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