Free-standing trimodal porous NiZn intermetallic and Ni heterojunction as highly efficient hydrogen evolution electrocatalyst in the alkaline electrolyte

Abstract

Intermetallics have attracted considerable research interests in a variety of electrocatalysis reactions due to their specific activity, selectivity, and stability arising from more severe alternation of electronic structure than substitutional alloys. Herein, we report one free-standing trimodal porous β₁-NiZn intermetallic and Ni heterostructure on Ni foam (TMP NiZn-Ni/NF) for hydrogen evolution reaction (HER) via electrochemical water-alkali splitting through one convenient and scalable dealloying strategy. Benefitting from high density reactive sites and fluent mass transfer as a result of trimodal porous architecture and strong electronic modulation from NiZn intermetallic, TMP NiZn-Ni/NF primely overcomes the sluggish hydrogen evolving kinetics with superior catalytic performances comparable to Pt/C and many other reported similar electrocatalysts. TMP NiZn-Ni/NF only required the low overpotential of 233 mV at high rate of 600 mA cm⁻² with the small Tafel slope at 47.3 mV dec⁻¹ in 1.0 M KOH solution. TMP NiZn-Ni/NF also exhibits exceptional catalytic durability toward HER with almost no current loss under the overpotential of 100 mV for 50 h. Theoretical calculations reveal that β₁-NiZn intermetallic itself has low Gibbs free energy for H adsorption (ΔG_H*), while it can also greatly decrease the ΔG_H* of heterojuncted Ni. This work presents one powerful and scalable protocol to screen self-supporting nonprecious intermetallic nanocatalysts with high density active sites and outstanding catalytic efficiency.