Determination of Electroactive Surface Area of Ni-, Co-, Fe-, and Ir-based Oxide Electrocatalysts

Metal oxides are important functional materials with a wide range of applications, especially in the field of electrocatalysis. However, quick and accurate assessment of their real electroactive surface area (ECSA), which is of paramount importance for the evaluation of their performance, remains a challenging task. Herein, we present a relatively simple strategy for an accurate in situ determination of the ECSA of commonly used metal oxide catalysts, namely: Ni-, Co-, Fe-, Pt- and Ir-based oxides. Similar to the well-established practice in electrocatalysis, the method is based on the phenomenon of specific adsorption. It uses the fact that at the electrode potentials close to the onset of the oxygen evolution reaction (OER), specifically adsorbed reaction intermediates manifest themselves through so-called adsorption capacitance, which is unambiguously detectable using electrochemical impedance spectroscopy. We determined and calibrated these capacitances for common catalyst metal oxides using model thi...