Facile synthesis of cubic Ni1-xCrxnanoalloys and their composition-dependent electrocatalytic activity for the hydrogen evolution reaction.

Abstract

The viability of the electrolysis of water currently relies on expensive catalysts such as Pt that are far too impractical for industrial scale use. Thus, there is considerable interest in developing low-cost, earth-abundant nanomaterials and their alloys as a potential alternative to existing standard catalysts. To address this issue, a synergistic approach involving theory and experiment was carried out. The former, based on density functional theory, was conducted to guide the experiment in selecting the ideal dopant and optimal concentration by focusing on 3d, 4d, and 5d elements as dopants on Ni (001) surface. Subsequently, a series of Ni_1-xCr_x(x= 0.01-0.09) alloy nanocrystals (NCs) with size ranging from 8.3 ± 1.6-18.2 ± 3.2 nm were colloidally synthesized to experimentally investigate the hydrogen evolution reaction (HER) activity. A compositional dependent trend for electrocatalytic activity was observed from both approaches with Ni_0.92Cr_0.08NCs showed the lowest ΔG_Hvalue and the lowest overpotential (η_-10) at -10 mA cm^-2current density (j), suggesting the highest HER activity among all compositions studied. Among alloy NCs, the highest performing Ni_0.92Cr_0.08composition displayed a mixed Volmer-Heyrovsky HER mechanism, the lowest Tafel slope, and improved stability in alkaline solutions. This study provides critical insights into enhancing the performance of earth-abundant metals through doping-induced electronic structure variation, paving the way for the design of high-efficiency catalysts for water electrolysis.