Ultrathin carbon-embedded nickel oxide layer encapsulating sponge-like nickel for alkaline hydrogen oxidation

Abstract

For hydrogen oxidation reaction (HOR), the kinetics in alkaline media is much sluggish than that in acidic media, and its catalyst mainly relies on noble metal-based materials, so it is of great significance to develop non-noble metal-based efficient HOR catalysts. In this work, based on the strong coordination interaction between transition metal cation and ligand molecule with lone pair electrons, a novel type of nickel-based aerogel-like material (Ni@NiO/C-400) is elaborately constructed. The material is composed of a spongy three-dimensional skeleton and a coated ultrathin layer，while the former is formed by the interconnection of metallic nickel nanorods and the latter contains nickel oxide species and embedded graphitic carbon island. The Ni@NiO/C-400 present certain exchange current density, kinetic current density and mass activity, implying obvious HOR activity. Based on the physicochemical characterization results, the Ni/NiO interface layer is formed on the catalyst surface and is supposed to provide moderate binding energy for H∗ and OH∗ and proposed to be a crucial origin of activity. Due to the accessible adsorption of intermediate species, exposure of active sites and protection for metallic nickel from over-oxidation, along with the favorable electronic conductivity enabled by the embedded graphitic carbon, the unique uneven thin layer on the catalyst surface also plays an important role in catalyzing HOR. Additionally, the three-dimensionally porous nickel framework endows abundant channels for electron transport and mass transfer during alkaline HOR process. The material-architecting strategy proposed in this work paves a new avenue for the rational design of non-noble metal catalysts.