First electrochemical synthesis of mesoporous RhNi alloy films for an alkali-mediated hydrogen evolution reaction

Abstract

Synthesizing mesoporous alloys composed of metals with divergent reactivities and standard redox potentials (E⁰) is challenging because the kinetics of metal deposition is totally different. Herein, we report the first method to generate mesoporous RhNi alloy films via electrochemical co-deposition using self-assembled micelle templates. The concentration of Rh precursor (Rh³⁺) is crucial to control reaction kinetics and morphology because Rh deposition is the trigger of Ni co-deposition. The ratio of Rh³⁺ : Ni²⁺ (in the precursor) can be altered to generate different alloy compositions, and the impact of pH and deposition potentials is also investigated. We examine the mesoporous RhNi films as electrocatalytic electrodes for the hydrogen evolution reaction (HER). Ni-doping serves to enhance the HER performance of the mesoporous films, and the 1 : 1 alloy (mesoporous Rh₄₉Ni₅₁ film) shows the best performance with the overpotential of 59 mV @ 10 mA cm⁻² and Tafel slope of 67 mV dec⁻¹. The insight gained here will enable researchers to experiment with different noble-transition metal alloys to generate better porous electrodes for electrocatalysis.