In Situ Construction of Biphasic Boride Electrocatalysts on Dealloyed Bulk Ni–Mo Alloy as Self-Supporting Electrode for Water Splitting at High Current Density

Nickel-molybdenum-boron (Ni-Mo-B)-based catalysts with biphasic interfaces are highly advantageous in bifunctional electrocatalytic activity in alkaline water-splitting. However, it remains an ongoing challenge to obtain porous Ni-Mo alloy substrates that provide stable adhesion to catalysts, ensuring the long-term performance of bifunctional self-supporting electrodes at a high current density. Herein, a porous Ni-Mo alloy substrate was effectively obtained by a cost-effective dealloying process on a commercial Ni-Mo alloy with high-energy crystal planes. Subsequently, the Mo2NiB2/Ni3B bifunctional catalyst was in situ synthesized on this substrate via boriding heat treatment, resulting in outstanding catalytic activity and stability. Density functional theory (DFT) calculations reveal that the abundant biphasic interfaces and surface-reconstructed sites of the Mo2NiB2/Ni3B catalyst can decrease the energy barriers for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Thus, the designed self-supporting electrodes show bifunctional catalytic activity with overpotentials of 151 mV for HER and 260 mV for OER at a current density of 10 mA cm-2. Markedly, the assembled water electrolyzer can be driven up to 10 mA cm-2 at 1.64 V and maintain catalytic activity at a high current density of 1000 mA cm-2 for 100 h. The new strategy is expected to provide a low-cost scheme for designing self-supporting bifunctional electrodes with high activity and excellent stability and contribute to the development of hydrogen energy technology.