Tuning Hydrogen Binding on Ru Sites by Ni Alloying on MoO₂ Enables Efficient Alkaline Hydrogen Evolution for Anion Exchange Membrane Water Electrolysis

Abstract

Ruthenium (Ru)-based electrocatalysts have shown promise for anion exchange membrane water electrolysis (AEMWE) due to their ability to facilitate water dissociation in the hydrogen evolution reaction (HER). However, their performance is limited by strong hydrogen binding, which hinders hydrogen desorption and water re-adsorption. This study reports the development of RuNi nanoalloys supported on MoO₂, which optimize the hydrogen binding strength at Ru sites through modulation by adjacent Ni atoms. Theoretical simulations reveal that substituting Ni atoms for adjacent Ru atoms reduces the high hydrogen adsorption Gibbs free energy on Ru while maintaining a low energy barrier for water dissociation. As a result, the RuNi/MoO₂ catalyst shows excellent HER performance with a low overpotential of 51 mV at a current density of 100 mA cm⁻², outperforming commercial Pt/C. Furthermore, RuNi/MoO₂ demonstrates high turnover frequency (7.06 s^-1), mass activity (13.4 A mg^-1), and price activity (1030.77 A dollar^-1). In an AEMWE cell, RuNi/MoO₂ as the cathode catalyst achieves a current density of 1 A cm^-2 at 60 °C with just 1.7 V using 1 m KOH. This work highlights the potential of RuNi/MoO₂ for ultra-high mass activity in efficient AEMWE applications.