Reconstructing the electronic structure of nickel selenide by Cu incorporation for an enhanced alkaline hydrogen evolution reaction

Abstract

Nickel selenides have proven to be efficient electrocatalysts for catalyzing the hydrogen evolution reaction (HER) in alkaline water electrolysis, but their unsatisfactory durability in alkaline media calls for a strategic exploration of ways to improve their HER activity. Herein, tuning the electronic structure of hydrothermally synthesized nickel selenide with electrodeposited Cu (NCS/NF) is shown to be successful for HER for the first time. Introduction of Cu enabled this newly developed catalyst to deliver a current density of −10 mA cm⁻² with a lower overpotential of only 45 mV due to enhanced electron diffusivity over an extended surface area. The voltage-induced phase transition of nickel selenide with Cu exhibited a 2.5-fold increase in HER activity, which enabled this activity-tuned catalyst (AD NCS/NF) to surpass the state-of-the-art Pt at all potentials under identical conditions. When connected in a two-cell configuration, AD NCS/NF‖NiFeLDH required a cell voltage of only 1.48 V to deliver 50 mA cm⁻². Furthermore, XRD, XPS and XAS findings provide insights into the voltage-induced structural reorganization of NCS/NF during the accelerated degradation test, revealing superior HER activity with an improvement in the catalyst's durability over time. The unique regulation of crystalline facets in NCS/NF with an Se-enriched surface promotes the intrinsic activity for H₂ production.