Precise characterization of activities is crucial for benchmarking and mechanistic examinations of electrocatalysts. In this study, the importance of surface areas to correctly characterize the activities of electrocatalysts is discussed. Exemplified for the hydrogen evolution reaction (HER) on a smooth and porous gold electrode, normalization of the activity to the geometric surface areas of the electrodes lead to activities that deviate by orders of magnitudes. Normalization to the electrochemically active surface areas (ECSAs) as determined by capacitance measurements lead to similar activities. To verify if surface areas of different electrodes can be correctly estimated by capacitance measurements, we examined a choice of noble (Au, Pt, Rh, Ir) and non-noble (Ni, Co, Ti, Nb) metal electrodes. The capacitances of all examined metals are individually affected by potential and passivation layers or specific adsorption processes of ions and/or molecules. Thus, the measured capacitances often deviate from the double layer capacitance that is typically used to estimate the ECSA. Accordingly, capacitance measurements to estimate the ECSA must be carefully evaluated and can only be correctly applied in certain frameworks.
Preparation and Characterization of Porous Gold and Its Application as a Platform for Immobilization of Acetylcholine Esterase
