Exploring the role of cobalt in promoting the electroactivity of amorphous Ni-B nanoparticles toward methanol oxidation

In this paper, amorphous Ni-B nanoparticles doped with cobalt are successfully prepared by simple chemical reduction to investigate the mechanism by which cobalt enhances the electroactivity. Transmission electron microscopy (TEM) images indicate that the morphology of the Ni-B-(Co) amorphous nanoparticles is uniformly spherical, and that the particle size is about 10-15 nm. X-ray photoelectron spectra (XPS) show that Co electrons shifted to B and Ni. Subsequently, the electrocatalytic characteristics were investigated by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). The results show that the methanol electro-oxidation current of Ni-B-(Co) amorphous nanoparticles initially increased and decreased as the Co content increased. Ni-B-Co0.05 nanoparticles exhibited the best electrocatalytic activity for methanol oxidation. It is proposed that the role of cobalt in methanol catalysis on the surface of amorphous Ni-B-Co nanoparticles is initially to promote the generation of NiOOH by preferentially forming CoOOH. Meanwhile Co could increase the absorption ability of Ni 3d orbit toward the methanol and intermediates, and thus improve the catalytic activity toward methanol. Our study provides a theoretical guide concerning doped atoms raising the electroactivity of the methanol oxidation on amorphous Ni-B nanoparticles.