Switching alkaline hydrogen oxidation reaction pathway via microenvironment modulation of Ru catalysts.

Ruthenium (Ru) has emerged as a promising catalyst for alkaline hydrogen oxidation reaction (HOR). Nevertheless, its catalytic performance still remains substantially inferior to the requirements of practical applications. Strategic modulation of the Ru micro-environment offers significant potential for optimizing its intrinsic catalytic activity. In this study, by elaborately designing a micro-environment of asymmetrically coordinated cobalt single-atom (Co-NO-C) structures for Ru, the obtained Ru/Co-NO-C achieves an exceptional HOR activity of 0.98 mA μg, which is 4.5-folds higher than Pt/C and 3.4-folds higher than Ru/Co-N-C. Combined experimental and theoretical investigations uncover that the outstanding HOR activity originates from three positive influences brought by the precisely engineered asymmetric coordination of Co sites, as compared to the symmetric Co-N-C environment, i.e., (i) through the electronic interaction between Ru and Co-NO-C, the excessively high hydrogen binding energy (HBE) at Ru sites is suppressed, (ii) by lowering the d-band center of Co, the strong hydroxide binding energy (OHBE) on Co sites is alleviated and (iii) the hydrogen bonding network within the electronic double layer is more connective, facilitating the OH transfer to react with H, thus switching the HOR pathway from the OHBE mechanism to the apparent HBE mechanism. This work accentuates the critical role of microenvironment modulation in regulating the HOR pathway and provides a novel strategy for devising superior-performance HOR catalysts.