A branch-leaf-like hierarchical self-supporting electrode as a highly efficient catalyst for hydrogen evolution

Abstract

Inspired by the advanced branch-leaf hierarchical structure of natural trees, a composite catalyst with a branch-leaf-like hierarchical structure was reported for the first time. This catalyst, which grows on Ni foam, consists of NiCo alloy nanobranches and MoO_3−x nanoleaves embedded with MoNi₄ nanoparticles. The NiCo alloy nanobranches as an electron transfer highway can effectively improve the conductivity of the catalyst. The MoO_3−x nanoleaves not only provide HER active sites, i.e. water dissociation center (MoO_3−x) and H_ads adsorption/desorption center (MoNi₄), but also increase the specific surface area, expose more active sites and promote the mass transfer of the catalyst. Benefiting from the branch-leaf hierarchical structure and synergistic effect of the components, this composite catalyst exhibits high HER activity which is comparable to that of 20% Pt/C in the alkaline solution. It requires a very low overpotential (33 mV) to reach 10 mA cm⁻², and the Tafel slope is only 34 mV dec⁻¹. The HER activity of the catalyst in simulated seawater is better than that of 20% Pt/C. This work shows a meaningful reference for the design and synthesis of a high efficiency non-noble metal HER catalyst used in alkaline water electrolysis.