Synergetic Oxidized Mg and Mo Sites on Amorphous Ru Metallene Boost Hydrogen Evolution Electrocatalysis

Abstract

Ruthenium (Ru) is considered as a promising catalyst for the alkaline hydrogen evolution reaction (HER), yet its weak water adsorption ability hinders the water splitting efficiency. Herein, a concept of introducing the oxygenophilic MgO_x and MoO_y species onto amorphous Ru metallene is demonstrated through a simple one-pot salt-templating method for the synergic promotion of water adsorption and splitting to greatly enhance the alkaline HER electrocatalysis. The atomically thin MgO_x and MoO_y species on Ru metallene (MgO_x/MoO_y-Ru) show a 15.3-fold increase in mass activity for HER at the potential of 100 mV than that of Ru metallene and an ultralow overpotential of 8.5 mV at a current density of 10 mA cm⁻². It is further demonstrated that the MgO_x/MoO_y-Ru-based anion exchange membrane water electrolyzer can achieve a high current density of 100 mA cm⁻² at a remarkably low cell voltage of 1.55 V, and exhibit excellent durability of over 60 h at a current density of 500 mA cm⁻². In situ spectroscopy and theoretical simulations reveal that the co-introduction of MgO_x and MoO_y enhances interfacial water adsorption and splitting by promoting adsorption on oxidized Mg sites and lowering the dissociation energy barrier on oxidized Mo sites.