Novel self-supporting thin film electrodes of FeCoNiCrMn high entropy alloy for excellent oxygen evolution reaction

The characteristics of FeCoNiCrMn high entropy alloy lead to great significance in electrocatalytic oxygen evolution reaction (OER) of water splitting. However, the preparation process of high entropy alloy for OER electrocatalyst still has limitations. And thin films of metals prepared by magnetron sputtering has a large amount of defects which facilitate the formation of active sites. In this work, FeCoNiCrMn high entropy alloy self-supporting electrodes based on nickel foam were fabricated by magnetron sputtering and applied for OER. It is confirmed that there is an optimum deposition time for the best OER performance. Furthermore, the OER performance of FeCoNiCrMn high entropy alloy electrodes can be boosted by surface reconstruction through cyclic voltammetry. As is revealed by morphology and surface chemical state characterization, there are a large amount of high entropy hydroxides and oxyhydroxides formed on the surface of FeCoNiCrMn high entropy alloy electrodes after CV reconstruction. The FeCoNiCrMn high entropy alloy electrodes reconstructed by cyclic voltammetric can reach an overpotential of 282 mV and a Tafel slope of 64.3 mVdec−1. [Display omitted] •The thin films of high entropy alloy were prepared by magnetron sputtering.•The thin films were applied as self-supporting electrodes for water splitting.•High entropy oxyhydroxide nanosheets were formed during reconstruction.•Electrons in Fe and Mn transfer to Ni and Co after reconstruction.