Ultrafast Carbothermal Shock Constructing Ni3Fe1–xCrx Intermetallic Integrated Electrodes for Efficient and Durable Overall Water Splitting

The development of the electrocatalyst-integrated electrodes with HER/OER bifunctional activity is desirable to reduce the cost and simplify the system of the practical water electrolyzers. Herein, we construct a new type of Ni₃Fe_1-xCr_x (0 ≤ x < 0.3) intermetallic integrated electrodes for overall water splitting via an ultrafast carbothermal shock method. The obtained Ni₃Fe_0.9Cr_0.1/CACC electrode exhibits the optimum performance among all developed electrocatalyst electrodes in this work, and the overpotential is merely 239 mV for OER and 128 mV for HER at 10 mA cm^-2. In addition, the Ni₃Fe_0.9Cr_0.1/CACC electrode shows excellent durability during both OER and HER stability tests at a high current density of 100 mA cm^-2. An electrolyzer, which was assembled with Ni₃Fe_0.9Cr_0.1/CACC electrodes as both the anode and cathode, operates with a low cell voltage of 1.59 V at 10 mA cm^-2. It has been found that the impressive OER activity of Ni₃Fe_0.9Cr_0.1 nanoparticles (NPs) can be ascribed to the stimulative formation of the OER-active Ni³⁺/Fe³⁺ species by the substituted Cr, while the enhanced HER activity is caused by the Cr substitution, which decreases the water dissociation energy barrier. This work provides an ultrafast and facile strategy to develop electrocatalyst-integrated electrodes with low cost and impressive HER/OER bifunctional performance for overall water splitting.