Amorphous Ni-Based Nanoparticles for Alkaline Oxygen Evolution

Amorphous Ni79.2–xCoxNb12.5Y8.3 (x = 0 and 5 at %) nanoparticles were produced through a two-stage ball milling process for use as electrocatalysts in the alkaline oxygen evolution reaction (OER). Cyclic voltammetry demonstrated that these amorphous alloys have excellent long-term cyclic durability when compared to crystalline Ni and Ni95Co5. Potentiostatic polarization measurements showed that the catalytic performance of amorphous Ni74.2Co5Nb12.5Y8.3 was maintained by displaying a low overpotential of 346 mV at 10 mA cm–2 even after 10,000 cycles, while deactivation could be observed for the other catalysts. XPS analysis revealed that the retention of catalytic activity was attributed to the stabilization of β-NiOOH. Through transmission electron microscopy analysis, it was found that the surface of amorphous Ni74.2Co5Nb12.5Y8.3 remained amorphous, although definitive signs of electrochemically induced Nb leaching could be observed. The leaching of Nb aided the overall performance since Nb is not electrochemically active toward the OER and was solely added to facilitate the formation of an amorphous structure. These findings not only support the excellent long-term stability and activity of amorphous Ni74.2Co5Nb12.5Y8.3 nanoparticles toward the alkaline OER but also demonstrate how anodic cycling can be used to condition the surface of the catalyst.