3‐d Element Induced Charge Redistribution Within Bimetallic η‐Phase Carbides Leads to High Performance Electrocatalysts for Highly Efficient Anion Exchange Membrane Water Electrolysis

Cost-effective, highly efficient, and robust electrocatalysts are critical for prevailing of anion exchange membrane water electrolysis technology for green hydrogen production. Here, Ni and Fe are incorporated into tungsten carbides to form bimetallic η-phase carbides Ni₆W₆C and Fe₆W₆C, respectively, achieving remarkably low overpotentials of 37/204 and 203/296 mV at current densities of 10/500 mA cm^-2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, in 1 m KOH. With Ni₆W₆C and Fe₆W₆C serving as the cathode and anode catalysts, respectively, the anion exchange membrane water electrolyzer exhibits outstanding water electrolysis performances, achieving an ultrahigh current density of 2.8 A cm^-2 at 2 V and exhibiting ultra-stability of a continuous operation at a commercially relevant high current density of 0.5 A cm^-2 for 100 h without appreciable decay. Incorporation of Ni in Ni₆W₆C induces charge redistribution between Ni and W, leading to an upshift in hydrogen adsorption energy to near-ideal value of zero and a downshift in hydrogen desorption energy for fast release of hydrogen, both contributing to the high HER activities of Ni₆W₆C. In situ surface reconstruction of Fe₆W₆C to highly OER-active (Fe,W)OOH during OER operations gives rise to high OER activities of Fe₆W₆C.