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 NiC-Ni catalyst as a model, we found that the rapid surface migration of OH species from the positively charged NiC to the negatively charged Ni component played a decisive role in facilitating water formation. Such unprecedented surface migration of OH is induced by the large discrepancy between the local surface charge densities and interfacial environments of the NiC and Ni components under operating conditions. Benefiting from this, the resultant NiC-Ni exhibited outstanding mass activity for the alkaline HOR, which was approximately 19-fold and 21-fold higher than those of Ni and NiC, 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.