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Advancing Cr(VI) Electroreduction: A Redox Mediator to Catalyze the Electrochemical Reduction of Cr(VI) in Water While Preventing Fouling of Carbon Electrodes.

ABSTRACT: Hexavalent chromium is a contaminant of concern and is found in drinking water supplies. Electrochemical methods are well-suited to accomplish the reduction of toxic Cr(VI) to Cr(III). However, high overpotentials and plating of Cr(III) products on electrodes have stymied the development of efficacious purification methods. The Cr(VI) reduction reaction necessitates the transfer of multiple protons and electrons, which is accompanied by a high kinetic barrier. Following recent advances in the electrocatalytic energy storage community, we report that the use of [Fe(CN)₆]^3- as a small molecular electrocatalyst not only diminishes the overpotential for Cr(VI) reduction on carbon electrodes by 0.575 V, but also prevents electrode fouling by mediating solution-phase homogeneous electron transfers.

SUBMITTER: Stern CM

PROVIDER: S-EPMC10853914 | biostudies-literature | 2024 Feb

REPOSITORIES: biostudies-literature

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Advancing Cr(VI) Electroreduction: A Redox Mediator to Catalyze the Electrochemical Reduction of Cr(VI) in Water While Preventing Fouling of Carbon Electrodes.

Stern Callie M CM Abeythunga Malithi M MM Elgrishi Noémie N

ACS organic & inorganic Au 20231106 1

Hexavalent chromium is a contaminant of concern and is found in drinking water supplies. Electrochemical methods are well-suited to accomplish the reduction of toxic Cr(VI) to Cr(III). However, high overpotentials and plating of Cr(III) products on electrodes have stymied the development of efficacious purification methods. The Cr(VI) reduction reaction necessitates the transfer of multiple protons and electrons, which is accompanied by a high kinetic barrier. Following recent advances in the el ...[more]

PMID: 38344011

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Project description:Understanding how crystallographic orientation influences the electrocatalytic performance of metal catalysts can potentially advance the design of catalysts with improved efficiency. Although single crystal electrodes are typically used for such studies, the one-at-a-time preparation procedure limits the range of secondary crystallographic orientations that can be profiled. This work employs scanning electrochemical cell microscopy (SECCM) together with co-located electron backscatter diffraction (EBSD) as a screening technique to investigate how surface crystallographic orientations on polycrystalline copper (Cu) correlate to activity under CO2 electroreduction conditions. SECCM measures spatially resolved voltammetry on polycrystalline copper covering low overpotentials of CO2 conversion to intermediates, thereby screening the different activity from low-index facets where H2 evolution is dominant to high-index facets where more reaction intermediates are expected. This approach allows the acquisition of 2500 voltammograms on approximately 60 different Cu surface facets identified with EBSD. The results show that the order of activity is (111) < (100) < (110) among the Cu primary orientations. The collection of data over a wide range of secondary orientations leads to the construction of an "electrochemical-crystallographic stereographic triangle" that provides a broad comprehension of the trends among Cu secondary surface facets rarely studied in the literature, [particularly (941) and (741)], and clearly shows that the electroreduction activity scales with the step and kink density of these surfaces. This work also reveals that the electrochemical stripping of the passive layer that is naturally formed on Cu in air is strongly grain-dependent, and the relative ease of stripping on low-index facets follows the order of (100) > (111) > (110). This allows a procedure to be implemented, whereby the oxide is removed (to an electrochemically undetectable level) prior to the kinetic analyses of electroreduction activity. SECCM screening allows for the most active surfaces to be ranked and prompts in-depth follow-up studies.

Dataset Information

Advancing Cr(VI) Electroreduction: A Redox Mediator to Catalyze the Electrochemical Reduction of Cr(VI) in Water While Preventing Fouling of Carbon Electrodes.

Publications

Advancing Cr(VI) Electroreduction: A Redox Mediator to Catalyze the Electrochemical Reduction of Cr(VI) in Water While Preventing Fouling of Carbon Electrodes.

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