Electrochemical Characterization of 316L Stainless Steel Electrodes for Alkaline Water Electrolysis in Renewable Energy Applications
Abstract
Abstract Electrochemical characterization of 316L stainless steel electrodes for alkaline water electrolysis was conducted through impedance spectroscopy (10 mHz–100 kHz), Tafel analysis, and thermal modeling. Impedance measurements revealed charge transfer resistance of 2.8 ± 0.2 Ω cm2, five-fold higher than ohmic resistance (0.52 ± 0.03 Ω cm2), identifying kinetic limitations as the primary optimization target. Tafel analysis demonstrated Volmer step rate-limitation with slopes of 130 ± 5 mV/decade for hydrogen evolution reaction (HER) and 85 ± 3 mV/decade for oxygen evolution reaction (OER), indicating water dissociation as the critical kinetic barrier. Exchange current densities of (2.3 ± 0.3) × 10–7 A/cm2 (HER) and (5.8 ± 0.5) × 10–6 A/cm2 (OER) were determined. Temperature-dependent measurements yielded activation energies of 48 ± 3 kJ/mol (HER) and 35 ± 2 kJ/mol (OER). A six-cell 5 kW electrolyzer system achieved 68.5% thermodynamic efficiency (LHV basis) with an 8.5-min thermal time constant. Field validation over 12 months in Turkey and Uzbekistan demonstrated operational stability exceeding 5100 h with hydrogen production at 62% DC-to-hydrogen efficiency when directly coupled with photovoltaic systems. The electrochemical characterization provides fundamental understanding of 316L stainless steel as a cost-effective electrode material for alkaline electrolysis in renewable energy applications.