Increased Oxygen Evolution Activity in <scp>pH‐Universal</scp> Electrocatalyst: <scp>Urea‐Modified NiFeCoCN Medium‐Entropy</scp> Alloy<sup>†</sup>
Hongwei Lv, Zhiguo Ye, Feng Pei, Xinyuan Peng, Juntong Huang, Duosheng Li, Zhong Jin
Abstract
Comprehensive Summary The kinetic process of a slow oxygen evolution reaction (OER) always constrains the efficiency of overall water electrolysis for H 2 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 IrO 2 /Ti electrode (58.6 mV·dec –1 ) in a 0.5 mol/L H 2 SO 4 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 IrO 2 /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 H 2 energy.