Abstract

Amorphous high-entropy alloys (HEA) are promising electrocatalysts with multi-element active sites and dense defect distribution, high valences of 3d transition metals (3d TMs) are beneficial for the oxygen evolution reaction (OER). However, it is still unknown how to enhance the 3d TMs valence state in amorphous HEA to improve OER catalytic activity. Herein, we successfully boosted the valence state of 3d TMs in HEA through electronegativity. The prepared FeCoNiMnW HEA exhibited significant amorphous characteristics. X-ray photoelectron spectroscopy analysis confirmed the formation of Ni3+ sites after adding electronegative W and the widespread occurrence of oxygen vacancies through amorphization. The enhanced oxidation state of Ni reduced the overpotential, while the abundant oxygen vacancies significantly facilitated electron transfer and thus boosting the rate of catalytic reactions. These characteristics lead to the amorphous FeCoNiMnW HEA exhibiting excellent OER performance. Amorphous FeCoNiMnW HEA films deposited on carbon cloth loaded with carbon nanotubes (FeCoNiMnW@CCC) only require an overpotential of 253 mV to generate a current density of 10 mA cm−2, which is much lower than RuO2 films (399 mV) and commercial RuO2 (309 mV), and shows excellent durability for 700 h at 20 mA cm−2 and 100 h at 200mA cm−2. This work provides a novel strategy for designing high-performance OER catalysts through structural and electronic modulation.

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