Abstract
The world is facing a continued increase in population that is accompanied by a high demand for energy. The dependence on fossil fuels caused demand and environmental crises. Therefore, it is necessary to switch to sustainable, clean, and renewable sources of energy immediately. Using hydrogen as a fuel is considered the most cleanest and promising alternative. Producing hydrogen using water electrolysis is the most environmentally friendly and sustainable method, especially when the electricity is generated from renewable sources. Employing electrolysis for hydrogen production is currently limited due to its high cost and low efficiency. For improving the efficiency of the electrolyzers and significantly decreasing the cost, it is necessary to increase the rate of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) by designing more active, stable, easy-to-fabricate electrocatalysts that are bifunctional and could be commonly fabricated for both the HER and OER.The different stainless steel (SS) alloys are common and inexpensive Fe-Ni-based alloys that recently attracted attention not only as conductive substrates for HER and OER catalysts but as electrocatalysts themselves.1 Untreated SS is poorly active towards HER or OER and needs further modification, such as electrochemical anodization followed by high-temperature annealing in different gases, to reach an acceptable activity.2,3 Anodized SS annealed under O2 is shown to be catalytically active towards OER while annealing under H2 is required for HER activity.2,3 Herein, the effect of anodizing the SS316 and SS304 alloys at different potentials and bath compositions (H2O, NH4F, H2SO4, and H3PO4 contents) on the electrode morphology and surface composition will be discussed. The anodized SS electrodes are annealed in different thermal annealing atmospheres (O2, and H2) and annealing temperatures (400-800 Cº). The physical/chemical structure of as received SS (R-SS), the annealed SS (A-SS), the anodized SS (AN-SS), and the anodized-annealed SS (A-AN-SS) electrodes were evaluated using XRD, FESEM, EDS, and XPS. The electrocatalytic behavior of the SS electrodes towards HER and OER in Alkaline solutions is evaluated using cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronopotentiometry (CP), and electrochemical impedance spectroscopy (EIS). The results will be discussed thoroughly to correlate the electrochemical behavior to the electrode morphology and surface composition.
Published Version
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