Restructuring of Cobalt Telluride Electrocatalysts in the Oxygen Evolution Reaction

Abstract

Among non-noble metals, transition metal chalcogenide electrocatalysts have high electrocatalytic performance and electrical conductivity, but they experience restructuring in oxidative oxygen evolution reaction (OER) conditions. Unfortunately, it is unknown what triggers such restructuring. In this study, we used cobalt telluride (CoTe) as a model system and combined in situ X-ray absorption spectroscopy with ex situ characterizations and DFT calculations to understand the restructuring mechanism. Results suggest that restructuring starts when CoTe is immersed in KOH solution and involves the transformation of Co–Te into Co–O bonds, suggesting that the true OER-active phases derived from CoTe are cobalt oxides or (oxy)hydroxides. The combined data are consistent with restructuring involving Te loss and oxygen incorporation at under-coordinated sites. Leached Te is detected in the electrolyte, while residual oxidized Te-containing species remain associated with the catalyst after restructuring. These observations are consistent with partial Te redeposition and/or retention of Te-containing surface species, which could influence the overall activity. Model-based analysis of the in-situ extended X-ray absorption fine structure spectra and XANES linear combination fitting suggests that the dominant reconstructed phases are Co3O4-like and CoOOH-like species that contribute to OER activity.