Understanding the Catalytic Active Sites of Crystalline CoSbxOy for Electrochemical Chlorine Evolution

Heng Dong; Xiaohan Shao; Shane Hancox; Sean T McBeath; William A Tarpeh; Michael R Hoffmann

doi:10.1021/acsami.3c05016

Understanding the Catalytic Active Sites of Crystalline CoSb_xO_y for Electrochemical Chlorine Evolution

ACS Appl Mater Interfaces. 2023 Aug 30;15(34):40369-40377. doi: 10.1021/acsami.3c05016. Epub 2023 Aug 18.

Authors

Heng Dong¹, Xiaohan Shao², Shane Hancox³, Sean T McBeath³, William A Tarpeh^{2

4}, Michael R Hoffmann¹

Affiliations

¹ Linde Laboratories, California Institute of Technology, Pasadena, California 91125, United States.
² Department of Civil and Environmental Engineering, Stanford University, Stanford, California 94305, United States.
³ Department of Civil and Environmental Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States.
⁴ Department of Chemical Engineering, Stanford University, Stanford, California 94305, United States.

Abstract

The chlorine evolution reaction (CER) is a key reaction in electrochemical oxidation (EO) of water treatment. Conventional anodes based on platinum group metals can be prohibitively expensive, which hinders further application of EO systems. Crystalline cobalt antimonate (CoSb_xO_y) was recently identified as a promising alternative to conventional anodes due to its high catalytic activity and stability in acidic media. However, its catalytic sites and reaction mechanism have not yet been elucidated. This study sheds light on the catalytically active sites in crystalline CoSb_xO_y anodes by using scanning electrochemical microscopy to compare the CER catalytic activities of a series of anode samples with different bulk Sb/Co ratios (from 1.43 to 2.80). The results showed that Sb sites served as more active catalytic sites than the Co sites. The varied Sb/Co ratios were also linked with slightly different electronic states of each element, leading to different CER selectivities in 30 mM chloride solutions under 10 mA cm^-2 current density. The high activity of Sb sites toward the CER highlighted the significance of the electronic polarization that changed the oxidation states of Co and Sb.

Keywords: chlorine evolution reaction; electrocatalysis; electrochemical oxidation; electrolysis; scanning electrochemical microscopy; water treatment.