Sulfur-Doped Nickel–Iron LDH@Cu Core–Shell Nanoarrays on Copper Mesh as High-Performance Electrocatalysts for Oxygen Evolution Reaction

The oxygen evolution reaction (OER) is a slow step in electrocatalytic water splitting. NiFe layered double hydroxides (LDH) have shown promise as affordable OER electrocatalysts, but their performance is hindered by poor charge transfer and sluggish kinetics. To address this, we doped NiFe LDH with sulfur (S) using an in situ electrodeposition method. By growing S-doped NiFe LDH on Cu nanoarrays, we created core–shell structures that improved both the thermodynamics and kinetics of OER. The resulting S-NiFe LDH@Cu core–shell nanoarrays exhibited enhanced activity in water oxidation, with a low potential of 236 mV (at 50 mA cm−2) and a small Tafel slope of 50.64 mV dec−1. Moreover, our alkaline electrolyzer, based on these materials, demonstrated remarkable activity, with a low voltage of 1.56 V at 100 mA cm−2 and excellent durability. The core–shell nanoarray structures provided a larger electroactive surface area, facilitated fast electron transport, and allowed for effective gas release. These findings highlight the potential of S-NiFe LDH@Cu core–shell nanoarrays as efficient OER electrocatalysts.