Lattice Mismatch Guided Nickel‐Indium Heterogeneous Alloy Electrocatalysts for Promoting the Alkaline Hydrogen Evolution

Lattice mismatch guides the selective alloying of tetragonal In to fcc Ni rather than hcp Ni. The heterogeneous alloy with 5 at% In catalyzes the electrochemical production of 153 mL h⁻¹ H₂ at −385 mV with 9.15 H₂ s⁻¹ turnover frequency at 400 mV vs. RHE in 1 M KOH.

Abstract

The immiscibility of crystallographic facets in multi-metallic catalysts plays a key role in driving the green H₂ production by water electrolysis. The lattice mismatch between tetragonal In and face-centered cubic (fcc) Ni is 14.9 % but the mismatch with hexagonal close-packed (hcp) Ni is 49.8 %. Hence, in a series of Ni−In heterogeneous alloys, In is selectively incorporated in the fcc Ni. The 18–20 nm Ni particles have 36 wt % fcc phase, which increases to 86 % after In incorporation. The charge transfer from In to Ni, stabilizes the Ni⁰ state and In develops a fractional positive charge that favors *OH adsorption. With only 5 at% In, 153 mL h⁻¹ H₂ is evolved at −385 mV with mass activity of 57.5 A g⁻¹ at—400 mV, 200 h stability at −0.18 V versus reversible hydrogen electrode (RHE), and Pt-like activity at high current densities, due to the spontaneous water dissociation, lower activation energy barrier, optimal adsorption energy of OH⁻ ions and the prevention of catalyst poisoning.

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