Chemical etching induced microporous nickel backbones decorated with metallic Fe@hydroxide nanocatalysts: an efficient and sustainable OER anode toward industrial alkaline water-splitting

Development of cost-effective and highly efficient electrocatalysts for water splitting is crucial to produce affordable and sustainable green-hydrogen energy that can alleviate the current overreliance on fossil fuels. This work demonstrates the simple immersion-based chemical etching of nickel foam (NF) in an ethanolic FeCl₃ solution to generate microporous nickel (Ni) backbones decorated with hierarchically structured metallic Fe doped Ni-Fe-hydroxide nanoparticles serving as a highly promising oxygen evolution reaction (OER) electrode in alkaline water. The optimally etched NF-based OER electrode exhibits a low Tafel slope of 47.3 mV dec⁻¹ and a low overpotential of 220, 270, and 310 mV at 10, 100, and 500 mA cm⁻², respectively. Intriguingly, this electrode also exhibits a perfectly reversible OER and HER performance between +400 and −40 mA cm⁻² with no evidence of electrode potential decay for 80 h. Importantly, when used with an industrial-type 30 wt% KOH aqueous electrolyte and compared to a benchmark Pt/C(20wt%)‖IrO₂-based cell, the electrolyzer exhibits a lower cell voltage of 1.52 (vs. 1.56 V of Pt/C(20wt%)‖IrO₂-cell), 1.62 (vs. 1.79), 1.69 (vs. 1.92) and 1.79 (vs. 2.08) V at 10, 50, 100, and 240 mA cm⁻², respectively, with the cell voltage maintained for ∼100 h.