A freestanding nanoporous NiCoFeMoMn high-entropy alloy as an efficient electrocatalyst for rapid water splitting

Abstract The development of low-cost non-noble metal-based electrocatalysts that can work stably at high current densities for the application of Hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in electrolyzed water is paramount crucial. Herein, we report a free-standing nanoporous high entropy alloy foil as dual-functional electrocatalyst via a combination of one-step dealloying and polarization, which exhibits excellent electrocatalytic activity in alkaline electrolyte with an extremely small overpotential of 150 mV at 1000 mA cm-2 for HER and a low Tafel slope of 29 mV dec-1 in 1 M KOH solution; At the same current density, the overpotential of OER is only 350 mV. The alkaline electrolyzer using it as both anode and cathode only need a cell voltage of 1.47 V to output a stable current density of 10 mA cm-2, enabling it as an efficient bifunctional electrocatalyst for alkaline overall water splitting, and remarkably better stability for more than 375 hours of continuous hydrogen production while providing substantial material cost savings relative to platinum. DFT calculations indicate that the ultrahigh HER activity of catalyst is originated from the synergetic effect of optimized hydrogen adsorption in the segregation area and enhanced H2O adsorption in the un-segregation area produced by spinodal decomposition.