Study on Crystallinity of Iron Oxide Coatings Obtained by Magnetron Sputtering to Form Efficient Thin-Film Catalysts for Oxygen Evolution

Thin films of iron oxide were formed on a stainless-steel substrate using magnetron sputtering (MS) technique from a pure hematite (Fe2O3,> 99.9 %) target with a pulsed direct current (PDC) regime at 300 W. Synthesis was carried out at pure argon atmosphere (for amorphous coating) and with a supply of oxygen (for crystalline and more stoichiometric coating). The as-deposited samples were thermally treated at 350 °C for 2 h to enhance the crystallinity and stoichiometry. Electrochemical oxidation at 5 mA cm−2 current density with supply of O2 gas was applied to saturate crystal lattices of the coatings with oxygen. Electrocatalytic evaluation of all samples indicated the advantage of amorphous structure over crystalline one, as it was able to operate at lower overpotentials (324 mV vs 336 mV at onset potential), exhibiting better process kinetics, and lower charge transfer resistance. A 24-h generation of oxygen at 10 mA cm−2 indicated the great stability of hematite structures, both amorphous and crystalline, as the samples maintained the stable potential without signs of deterioration. © 2025 Elsevier Ltd and Techna Group S.r.l. All rights are reserved, including those for text and data mining, AI training, and similar technologies.