Hydrogen Evolution Reaction in Alkaline Media: Alpha- or Beta-Nickel Hydroxide on the Surface of Platinum?

Reducing the energy consumption of a hydrogen evolution reaction (HER) at a platinum (Pt) electrode is important for the hydrogen economy. Herein, we report the loading of alpha- or beta-nickel hydroxide (α- or β-Ni(OH)₂) nanostructures on the surface of a Pt electrode to improve its catalytic activity and stability for HER in alkaline electrolytes. Both experimental and theoretical studies reveal that β-Ni(OH)₂ is a better co-catalyst of Pt than α-Ni(OH)₂ for promoting the HER, attributed to the higher water dissociation ability of β-Ni(OH)₂, as well as the stronger interactions between β-Ni(OH)₂ and the Pt electrode. Particularly, the overpotential of the HER in 0.1 M KOH at 10 mA cm^-2 is decreased from 278 mV at the Pt electrode to 92 mV at the β-Ni(OH)₂/Pt electrode, and the Tafel slope decreased from 62 to 42 mV dec^-1, correspondingly. The performance of the β-Ni(OH)₂/Pt catalytic electrode surpasses that of most of the previously reported electrodes for the same purpose.