Dual Modulation of Hydroxyl Action on Ruthenium Surface by Single-Atom Supports for Alkaline H₂ Evolution

Ruthenium (Ru)-based catalysts are known to accelerate the slow kinetics of the alkaline hydrogen evolution reaction (HER). However, enhancing the transfer kinetics of adsorbed hydroxyl (OH_ad) remains challenging. Herein, a dual-regulation strategy is presented to alleviate OH blockage on the catalyst surface, using a cluster-level Ru electrocatalyst supported by single-atom CoN₄ generated in situ on carbon nanotubes (CNTs). Experimental and theoretical studies demonstrate that introducing oxophilic single-atom CoN₄ can mitigate the strong interaction between Ru and OH_ad by directly competing for OH_ad on the Ru surface, thereby preventing Ru site poisoning. Meanwhile, single-atom CoN₄ effectively modifies the electronic structure of Ru atomic clusters (ACs), indirectly optimizing the energy barriers for OH desorption at the Ru interface and promoting OH_ad release. The electronic interaction between Ru ACs and CoN₄ also inhibits Ru atom migration, significantly enhancing catalytic stability. The resulting catalyst shows excellent HER activity at 10 mA cm⁻² with a low overpotential of 15 mV in alkaline solution and remains stable at 200 mA cm⁻² for over 1000 h. An alkaline anion-exchange membrane water electrolyzer (AEMWE) using this catalyst can exhibit an ultralow potential (1.785 V at 1 A·cm⁻²) and high stability at 500 mA·cm⁻².