High-performance alkaline water splitting by Ni nanoparticle-decorated Mo-Ni microrods: Enhanced ion adsorption by the local electric field

Abstract

Hydrogen production by alkaline water electrolysis represents an effective route for low-cost and clean energy conversion. However, as hydrogen ions (H+) are the minority species in alkaline media, the kinetics of hydrogen evolution reaction (HER) is markedly reduced. Concurrently, the transport of hydroxide ions (OH–) is limited under large current density in alkaline oxygen evolution reaction (OER). Herein, Ni nanoparticles-decorated Mo-Ni microrods (Ni/Mo-Ni) are adopted to boost the ion adsorption. Finite-element simulations suggest that a strong local electric field around the Ni nanoparticles exponentially increases ion adsorption towards the electrode surface, which facilitates reaction kinetics and mass transfer for HER at the cathode and OER at the anode. Thus, the Ni/Mo-Ni electrode exhibits a low overpotential of only −24 mV for HER and + 215 mV for OER to reach the current density of 10 mA cm−2, and can achieve an industrial alkaline splitting current density of 100 mA cm−2 at a low voltage of 1.76 V and stably operate for 87 h. This work suggests a new paradigm in the design and engineering of high-performance catalysts for alkaline electrolyzers.