Increased Oxygen Evolution Activity in pH‐Universal Electrocatalyst: Urea‐Modified NiFeCoCN Medium‐Entropy Alloy†

Abstract

Comprehensive SummaryThe kinetic process of a slow oxygen evolution reaction (OER) always constrains the efficiency of overall water electrolysis for H2 production. In particular, nonprecious metal electrodes for the OER have difficulty in possessing excellent electrocatalytic activity and stability in pH‐universal media simultaneously. In this work, urea is first used as a pore‐forming agent and active C/N source to fabricate a nanoporous NiFeCoCN medium‐entropy alloy (MEA) by high‐temperature sintering based on the nanoscale Kirkendall effect. The NiFeCoCN MEA achieves an overpotential of 432 mV at a current density of 10 mA·cm–2 and a lower Tafel slope of 52.4 mV·dec–1 compared to the IrO2/Ti electrode (58.6 mV·dec–1) in a 0.5 mol/L H2SO4 solution. In a 1 mol/L KOH solution, the NiFeCoCN MEA obtains an overpotential of 175 mV for 10 mA·cm–2 and a Tafel slope of 40.8 mV·dec–1, which is better than IrO2/Ni foam. This work proves a novel strategy to design and prepare nanoporous MEA materials with desirable C/N species, which provides promising prospects for the industrial production of H2 energy.