Boosting Alkaline Hydrogen Oxidation Kinetics through Interfacial Environments Induced Surface Migration of Adsorbed Hydroxyl

Constructing bifunctional sites through heterojunction engineering to accelerate water formation has become a pivotal strategy to improve the alkaline hydrogen oxidation reaction (HOR) kinetics, which is mainly focused on the synergistic effect of neighboring sites and the energetics of the surface reaction steps. However, the roles of the surface migration of key intermediates that go beyond the bifunctional mechanism limited to neighboring atoms have usually been ignored. Using the heterostructured Ni₃C-Ni catalyst as a model, we found that the rapid surface migration of OH_ad species from the positively charged Ni₃C to the negatively charged Ni component played a decisive role in facilitating water formation. Such unprecedented surface migration of OH_ad is induced by the large discrepancy between the local surface charge densities and interfacial environments of the Ni₃C and Ni components under operating conditions. Benefiting from this, the resultant Ni₃C-Ni exhibited outstanding mass activity for the alkaline HOR, which was approximately 19-fold and 21-fold higher than those of Ni and Ni₃C, respectively. These findings not only provide novel insights into the alkaline HOR mechanism of heterostructured catalysts but also open new avenues for developing advanced electrocatalysts for alkaline fuel cells.