Sb incorporated into oxides enhances stability in acid during the oxygen evolution reaction by inhibiting structural distortion

Development of first-row transition-metal-based catalysts for oxygen evolution is a desirable goal due to the low cost and abundance of transition metals, relative to iridium. However, low stability of first-row transition metal catalysts in acidic electrolytes has impeded practical application. In this work, we proposed the role of Sb in metal oxide which enhance electrochemical stability in acid media. While a Co-Fe mixed oxide exhibited poor stability in acid, a FeCoSbO_x electrode demonstrate superior stability of over 70 h under the same conditions. In-situ/Operando analysis results suggest that distortion occurred in the FeCoO_x electrode under acidic conditions for oxygen evolution, while the structure of the FeCoSbO_x electrode was maintained. As compared to an SbO_x electrode, Sb in an FeCoSbO_x electrode had a higher oxidation state and shorter lattice distance, indicating strong Sb-O bonding. Given the stronger oxide bond, we anticipated that incorporation of Sb would enhance stability in acidic media not only via greater thermodynamic stability but by inhibiting distortion during the reaction. A more stable structure prevents participation by lattice oxygen, resulting in enhanced electrode stability. This demonstration of a stabilizing structural element in a transition metal oxide offers new principles for designing electrocatalysts that are stable in acidic media.