Surface-Engineered Porous Electrodes for High-Performance Alkaline Water Splitting

Abstract This study presents a simple and scalable surface modification strategy to enhance the performance of nickel foam (NF) for alkaline water splitting. By employing a concentrated aqueous FeCl3 etchant, we achieved anisotropic etching that preferentially attacks the (111) facet, creating a striped surface morphology. This structural modification significantly increases surface hydrophilicity and reduces gas bubble departure size by approximately 31%, facilitating superior mass transport and minimizing active site blocking. Electrochemical testing demonstrates that NF etched for 30 minutes (NF30m) exhibits exceptional oxygen evolution reaction (OER) activity, achieving overpotentials of 262 mV and 485 mV at current densities of 10 and 1000 mA cm−2, respectively, a substantial improvement over pristine NF, with good stability over 20 h at 500 mA cm-2. Furthermore, a marked reduction in Tafel slope (from 66.7 to 36.0 mV dec−1) and increased charge transfer during Ni(II)/Ni(III) redox transitions suggest that the etching process promotes the formation of the highly active γ−NiOOH. These findings highlight surface engineering via controlled chemical etching as a potent route for developing high-efficiency, low-cost electrodes for industrial-scale hydrogen production.