Heterointerface engineered NiFe(OH)_x/Ni₃S₂ electrocatalysts to overcome the scaling relationship for ultrahigh-current-density water oxidation

Breaking the scaling relationship of water oxidation is the gateway to obtain an ultrahigh current density at a low potential for greatly improving the water electrolysis efficiency in industrial hydrogen production. Herein, we demonstrate a novel heterointerface engineered NiFe(OH)_x/Ni₃S₂ electrocatalyst to successfully circumvent the scaling relationship of the oxygen evolution reaction (OER), which significantly decreases the difference of the Gibbs free energy of HOO* and HO*(}ΔG_hoo*–ΔG_ho*) from 3.20 to 2.38 eV. To achieve an ultrahigh current density of 2000 mA cm⁻², the NiFe(OH)_x/Ni₃S₂ electrocatalyst requires a small overpotential of 310 mV with an ultralow Tafel slope of 20.8 mV dec⁻¹. It can also steadily operate under 1000 mA cm⁻² for over 100 h with insignificant activity loss, thus surpassing the state-of-the-art OER catalysts to date. A parallel catalytic mechanism has been disclosed to be responsible for the optimization of the reaction pathway, thus realizing the homogenization of multi-intermediate adsorption energy with extremely elevated OER catalytic performance at ultrahigh current densities. These findings could be a guidance in developing industrial-grade high-performance electrocatalysts for water splitting.