Fabrication of a eutectic high-entropy alloy bulk electrode with balanced activity and stability for OER via surface reconstruction

The oxygen evolution reaction (OER) in electrochemical water splitting has always been a key bottleneck restricting efficient hydrogen production. An ideal electrocatalyst must not only exhibit high catalytic activity but also possess excellent stability, which is an equally crucial core indicator. Therefore, developing electrocatalysts that simultaneously achieve both high activity and long-term stability is of great significance. In this study, we successfully prepared a bulk high-entropy alloy electrode with a fully eutectic structure using arc melting technology. By adjusting the relative ratios of Cr and Mo elements, we not only optimized the intrinsic catalytic activity of the electrode but also observed a unique "performance improvement over time" phenomenon during prolonged stability tests. The dense eutectic structure of the electrode provides an ideal environment for electronic interactions among multiple metal atoms. During CV activation, the applied voltage drives the dissolution of the "unstable" IMC phase in the electrode. The dissolution of the Mo-rich phase and the leaching of Cr ions enhance the degree of surface reconstruction, leading to the formation of active high-valence oxygen-containing species, thereby promoting the enhancement of OER performance. After activation via cyclic voltammetry (CV), the Cr10Mo06-A electrode exhibited the most remarkable performance improvement, requiring only an overpotential of 380 mV to achieve a current density of 400 mA cm −2 . Moreover, the electrode demonstrated continuous and stable operation for nearly 500 h at a high current density of 500 mA cm −2 , successfully achieving a synergy between high activity and outstanding stability.