Atomically Dispersed MoO_<i>x</i> on Rhodium Metallene Boosts Electrocatalyzed Alkaline Hydrogen Evolution

Accelerating slow water dissociation kinetics is key to boosting the hydrogen evolution reaction (HER) in alkaline media. We report the synthesis of atomically dispersed MoO_x species anchored on Rh metallene using a one-pot solvothermal method. The resulting structures expose the oxide-metal interfaces to the maximum extent. This leads to a MoO_x -Rh catalyst with ultrahigh alkaline HER activity. We obtained a mass activity of 2.32 A mg_Rh ^-1 at an overpotential of 50 mV, which is 11.8 times higher than that of commercial Pt/C and surpasses the previously reported Rh-based electrocatalysts. First-principles calculations demonstrate that the interface between MoO_x and Rh is the active center for alkaline HER. The MoO_x sites preferentially adsorb and dissociate water molecules, and adjacent Rh sites adsorb the generated atomic hydrogen for efficient H₂ evolution. Our findings illustrate the potential of atomic interface engineering strategies in electrocatalysis.