Modifying the 316L stainless steel surface by an electrodeposition technique: towards high-performance electrodes for alkaline water electrolysis

Abstract

The development of highly effective and stable non-precious electrodes for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in water splitting devices for hydrogen production is critical and a challenge for the process of energy storage and conversion. In this study, a stainless steel (SS) electrode has been modified using nickel phosphide (NiP) nanoparticles on its conductive surface through a fast and simple one-step electrodeposition process and utilized as a non-precious, binder-free, and robust electrode towards the OER and HER in alkaline solution. The deposition time was studied to examine its influence on the morphology of xNiP@SS (x refers to deposition time) and the corresponding catalytic performance of the OER and HER in 1.0 M KOH solution. Taking advantage of the superior morphology (homogeneity of the deposition and high porosity) with a high electrochemical surface area (ECSA) and excellent contact at the substrate/catalyst interfaces, the optimized xNiP@SS electrode exhibited excellent OER performance by achieving overpotentials of 238 and 271 mV at current densities of 10 and 100 mA cm⁻², respectively, with a Tafel slope of 41.24 mV dec⁻¹. For the HER, an overpotential of 268 mV can be reached at 10 mA cm⁻² with a Tafel slope of 70.5 mV dec⁻¹. The modified electrode showed higher stability for both reactions under the relevant electrolysis conditions for the OER and HER for 24 hours. Furthermore, an experimental lab electrolyzer based on the modified xNiP@SS electrodes as the anode and cathode has been tested, achieving a voltage of 1.77 V at 10 mA cm⁻². This work presents a rapid and straightforward strategy for the modification of the SS surface with metal phosphide to afford cost-effective, highly efficient, and stable electrodes for the OER and HER in water electrolyzer systems.