Iron-decorated nickel selenide nanostructures with enhanced electrocatalytic activity for the oxygen evolution reaction

In this contribution, we present the design of novel electrocatalysts for the oxygen evolution reaction (OER) consisting of nickel selenide nanowires decorated with iron-based species. The nickel-based nanowires were grown on Ni-foam through a selenidation process, followed by a hydrothermal treatment to introduce the Fe species (at 40, 80 or 120 °C). The resulting Fe–Ni3Se2/Ni-foam electrocatalysts exhibited high OER activity, with the material prepared at 40 °C (Fe–Ni3Se2/Ni-foam-40) showing the best performance by achieving 100 mA cm−2 at an overpotential of only 250 mV. Comprehensive characterization using XRD, Raman spectroscopy, SEM, TEM, ICP-AES and XPS revealed that the enhanced activity of Fe–Ni3Se2/Ni-foam-40 arises from its favourable composite morphology, featuring a combination of μm- and nm-sized structures, and from the effective incorporation of iron species, leading to a surface composition with a higher intrinsic OER activity. Importantly, Fe–Ni3Se2/Ni-foam-40 displayed excellent stability at an industrially-relevant current density of 500 mA cm−2 during a prolonged chronopotentiometric test (100 h). Throughout this period, the morphology of the catalyst was largely preserved, despite a gradual surface transformation from metal selenides to (oxy)hydroxides. Furthermore, the overall water-splitting performance of Fe–Ni3Se2/Ni-foam-40 was validated in a commercial lab-scale (5 cm2) anion-exchange membrane (AEM) electrolyzer cell. These results demonstrate that Fe–Ni3Se2/Ni-foam-40 is an efficient and stable electrocatalyst, offering great promise for alkaline water electrolysis.