Enhancement of oxygen evolution reaction performance of FeCoNiCrMn high entropy alloy thin film electrodes through in-situ reconstruction

Due to the large number of defects and high entropy properties, high entropy alloy thin film electrodes prepared by magnetron sputtering are beneficial for electrocatalytic oxygen evolution reaction (OER). However, the electrocatalytic OER performance of high entropy alloy thin film electrodes without activation is limited. In this work, in-situ reconstruction (chloride corrosion) is applied to activate FeCoNiCrMn high entropy alloy thin film electrodes for promoting the electrocatalytic OER performance. The research reveals that high entropy hydroxides and high entropy (oxy)hydroxides, which are real active centers of OER electrocatalysts, are generated on the surface of FeCoNiCrMn high entropy film electrodes during in-situ reconstruction. Moreover, it is also proved that there is an obvious quantitative relationship among elements in the surface of the high entropy alloy thin film electrodes after complex chloride corrosion reaction: Ni>Mn>Fe>Co>Cr. In addition, the OER performance of FeCoNiCrMn high entropy film electrodes with in-situ reconstruction can achieve an overpotential of 263 mV and a Tafel slope of 50.9 mVdec−1. Moreover, sponge-like structures created by in situ reconstitution can help to increase surface active areas and the increased contents of high-valence elements after in situ reconstruction contribute to enhance electrocatalytic OER activity.