Nickel nanoparticles supported on doped graphene-based materials for the ORR and HER in alkaline medium.

[Display omitted] • Heteroatoms in graphene-based materials modulate their electrochemical activity. • Supporting Ni on S,N-doped graphene decreases the HO 2 − route for ORR below 10% • Supporting Ni on doped graphene materials reduces HER overpotential ca. 0.50 V. • These Ni materials are promising electrocatalysts for alkaline PEM devices. In this work, Ni nanoparticles (NPs), with nominal metallic loading of 20 wt%, were deposited on graphene-based materials (GMs) doped with nitrogen and sulphur, in order to study their electrocatalytic activity towards the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) in alkaline medium. Different chemical reducing agents were employed to synthesize the catalysts. Results indicate that the presence of heteroatoms in the GMs influences the activity of both the GMs and the Ni-based catalysts. Thus, best results were obtained for catalyst containing nitrogen and sulphur for the ORR which favours the direct four-electron pathway, whereas for the HER, the highest performance was observed for N -doped materials. [ABSTRACT FROM AUTHOR]