Journal
ACS CATALYSIS
Volume 9, Issue 10, Pages 9222-9230Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.9b02006
Keywords
electrocatalysis; electrode surface area; oxide catalysts; ECSA determination; electrochemical impedance spectroscopy; iridium oxide; oxygen evolution reaction
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Funding
- Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germanys Excellence cluster e-conversion
- Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under TUM IGSSE cohort 11 (ActiveElectroCat) [11.01]
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Metal oxides are important functional materials with a wide range of applications, especially in the field of electro-catalysis. 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 electrode potentials close to the onset of the oxygen evolution reaction, 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 thin films. Therefore, with simple impedance measurements, experimentalists can acquire the adsorption capacitance values and accurately estimate the real electroactive surface area of the above-mentioned oxide materials, including nanostructured electrocatalysts. Additionally, as illustrative examples, we demonstrate the application of the method for the determination of the ECSA of oxide catalyst nanoparticles.
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