Excellent CoO_xH_y/C Oxygen Evolution Catalysts Evolved from the Rapid In Situ Electrochemical Reconstruction of Cobalt Transition Metals Doped into the V₂SnC MAX Phase at A Layers

Abstract

Transition metal (oxy)hydroxides are recognized as the most effective non-noble metal electrocatalysts for the alkaline oxygen evolution reaction (OER). However, their electrical conductivity and durability are insufficient for the development of electrochemical energy devices. Thus, constructing more compact and stable transition metal-based composite materials while maintaining high activity is still desperately needed. In this study, we propose a potent approach for producing highly active sites via alloying transition metals with carbon elements evolved from the MAX phases. We for the first time found an activation paradigm for such a phase (V2(Co x Sn1‑x )C) via an OER in situ polarization process. The mechanism is proposed as the Co element in the A site significantly facilitates the structural evolution of the pristine V2SnC phase. Compared with typical electrodeposited cobalt hydroxide (Co–H), such a MAX-derived catalyst exhibits better OER activity and lower valence charge transition potential owing to its unique nanocomposite structure, more exposed active sites, and better electric conductivity. Furthermore, the preparation of this catalyst is applicable to nickel foams. Our investigation confirmed its long-term stability and superior activity over most reported Co-based catalysts. This unique structural evolution route provides a potentially generalizable strategy for MAX phases as efficient electrocatalysts.