Spinel-type (MnFeCoNiZn)3O4 high-entropy oxide nanoparticles as efficient bifunctional electrocatalyst for hydrogen and oxygen evolution reactions in alkaline media

High entropy oxide nanoparticles (HEO NPs) have recently captured interest as attractive candidates for sustainable energy conversion technology. Their merits over the conventional metal oxides include the multi-element synergy and high configuration entropy. In this work, we report the (MnFeCoNiZn) 3 O 4 HEO NPs prepared by the solution combustion method and their application as a bifunctional electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in the alkaline media. The three different concentrations of the KOH electrolytes (0.1, 0.5, and 1 M KOH) were used to analyse the dependence of the reaction kinetics on the alkalinity of the electrolyte. The (MnFeCoNiZn) 3 O 4 HEO NPs electrocatalyst has delivered an improved electrocatalytic performance with an increase in the KOH concentration. The lower overpotentials and high current densities were achieved with the 1 M KOH due to its enhanced conductivity. In 1 M KOH, the (MnFeCoNiZn) 3 O 4 HEO NPs exhibited excellent catalytic performance toward HER with an overpotential of 141 mV with a Tafel slope of 118 mV dec −1 . And toward OER, an overpotential of 295 mV with a Tafel slope of 40 mV dec −1 (1.0 M KOH). Moreover, this electrocatalyst has maintained 40 hours long-term durability. The post-durability studies highlighted the suitability of (MnFeCoNiZn) 3 O 4 HEO NPs for practical water-splitting applications.