Lattice-Mismatched RuNi Alloy Nanoparticles with Enhanced Bifunctional Hydrogen Electrocatalysis for Nickel-H2 Batteries

Abstract Nickel-hydrogen gas (Ni-H2) batteries exhibit ultra-long cycle life, promising excellent prospects for applications in large-scale energy storage. However, traditional Pt-based catalysts face challenges in achieving both high activity and long-term stability in alkaline media, rendering the development of electrocatalysts with enhanced performanced for both hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR) a significant challenge. In this work, through a combination of rotary evaporation and thermal treatment, the optimized carbon-supported RuNi alloy nanoparticles (RuNi-1/C) have been synthesized, which enables to successfully realize a large lattice mismatch of up to 13.47%. This high lattice mismatch induces change in the interplanar spacing of Ru and Ni, thereby exposing more active sites and resulting in excellent bifunctional HER/HOR performance: it achieves an ultra-low overpotential of just 14.4 mV at a current density of 10 mA/cm2 for the HER and a high exchange current density of 2.13 mA/cm2 at an overpotential of 50 mV for the HOR. Furthermore, when employed as the bifunctional catalyst in a Ni-H2 battery, RuNi-1/C delivers a coulombic efficiency of 92% and outstanding cycling stability. This work offers a promising synthesis route toward the development of highly active and durable bifunctional catalysts by regulating the lattice mismatch.