Boosting Alkaline Hydrogen Evolution by Creating Atomic-Scale Pair Cocatalytic Sites in Single-Phase Single-Atom-Ruthenium-Incorporated Cobalt Oxide.

Abstract

Compared with acidic environments, promoting the water dissociation process is crucial for speeding up hydrogen evolution reaction (HER) kinetics in alkaline electrolyte. Although the construction of heterostructured electrocatalysts by hybridizing noble metals with metal (hydr)oxides has been reported as a feasible approach to achieve high performance, the high cost, complicated fabrication process, and unsatisfactory mass activity limit their large-scale applications. Herein, we report a single-phase HER electrocatalyst composed of single-atom ruthenium (Ru) incorporated into a cobalt oxide spine structure (denoted as Ru SA/Co₃O₄), which possesses exceptional HER performance in alkaline media via unusual atomic-scale Ru-Co pair sites. In particular, Ru SA/Co₃O₄ exhibits a very low overpotential of 44 mV at 10 mA cm^-2 and an outstanding mass activity of 4700 mA mg^-1 at 50 mV overpotential, superior to those of commercial Pt/C, Ru nanoparticles supported on Co₃O₄ (denoted as Ru NP/Co₃O₄) and other reported Ru-based electrocatalysts. With insights from theoretical calculations, the synergistic interactions between Ru and Co pair active sites in Ru SA/Co₃O₄ are revealed to catalyze diverse fundamental steps of the alkaline HER; i.e., the Ru sites can effectively accelerate water adsorption/dissociation and OH^- desorption, whereas the Co sites are favorable for H* adsorption and H₂ evolution.