Nanostructures and Oxygen Evolution Overpotentials of Surface Catalyst Layers Synthesized on Various Austenitic Stainless Steel Electrodes

We investigated oxygen evolution reaction (OER) overpotentials of surface catalyst layers synthesized on various austenitic stainless steel (SS303, 310S, and 316) electrodes by applying electrochemical pre-treatment (ET) in 1 M KOH electrolyte. The effects of the metal composition of SS electrode on the OER overpotentials and nanostructure of the resulting electrodes were discussed. Scanning transmission electron microscopic observations with energy dispersive spectroscopy showed that the fiber-like nanostructured surface catalyst layers and the Fe/Ni atomic ratios of the catalyst layers after ET were correlated with that of the starting SS electrode. The electrochemical double layer capacitance (C_dl) estimated after ET followed the order: 303 > 316 > 310S, and the C_dl-normalized OER overpotentials were almost the same for 310S and 316, whereas that of 303 was ca. 25 mV larger. The results suggest that the metal element composition, especially the Fe/Ni ratio of the bulk SS, is one of the key parameters determining the OER performance of SS-based anodes for alkaline water electrolyzers. Graphical abstract: [Figure not available: see fulltext.]