Construction of high-entropy oxy/hydroxides with dense nanosheet array structures on FeCoNiCrMo electrode for efficient oxygen evolution reaction

The high-entropy alloy (HEA) films prepared by magnetron sputtering on 3D substrates have excellent ability to release bubbles, good electrical conductivity, and abundant active sites, which lead to excellent performance in oxygen evolution reaction. HEA films with various elements were prepared on different substrates. In general, oxygen evolution reaction abilities of HEA film electrodes are related to morphologies of catalyst and types of active sites. Notably, nanostructures with regular array could help to increase the surface area of electrocatalysts and expose active sites. Also, chloride salt solution of transition metals can promote the formation of high-entropy oxy/hydroxides due to oxygen absorption oxidation reaction and displacement reaction on the surface of HEA film electrodes. And electrochemical oxidation at suitable high potential can also produce high-entropy oxy/hydroxides. In this work, dense nanosheet array structures of high-entropy oxy/hydroxides were constructed on the surface of FeCoNiCrMo HEA film electrodes preprocessed in NiCl₂ solution and reconstructed by electrochemical oxidation in KOH solution further. The FeCoNiCrMo HEA film electrode with dense nanosheet array structures has excellent OER performance with the overpotential of 250 mV, Tafel slope of 41.5 mV dec⁻¹, and electric double layer capacitance of 4.3