Prominent electronic effect in iridium-alloy-skinned nickel nanoparticles boosts alkaline hydrogen electrocatalysis

Alkaline hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) are scientifically important and practically relevant. They, unfortunately, suffer from sluggish reaction kinetics owing to the unfavorable adsorption of key reaction intermediates on existing electrocatalysts. Here, we show that the electronic effect incurred upon nanoscale alloying could remedy this challenge. Iridium-alloy-skinned nickel nanoparticles are prepared by a solvothermal method. These nanoparticles feature uniform size distribution and a unique core-skin structure with an atomic-layer-thick alloy skin. In alkaline solution, the catalyst exhibits extraordinary HOR activity with outstanding mass-specific kinetic and exchange currents 4-6 times higher than those of precious metal benchmark catalysts and significantly outperforming those of other precious metal based electrocatalysts. Most impressively, a broad HOR working potential window of up to 1 V is measured for the first time for iridium-based catalysts. The catalyst also demonstrates great HER activity requiring only η = 33 mV to reach 10 mA cm −2 . Theoretical simulations reveal that the prominent electronic effect in the alloyed skin modulates the *H and *OH adsorption energies, and thereby facilitates the bifunctional HOR/HER in alkaline solution. The prominent electronic effect between Ni and Ir in Ir-alloy-skinned Ni nanoparticles leads to excellent bifunctional HOR and HER activities in alkaline solution.