Analysis of oxygen evolving catalyst coated membranes with different current collectors using a new modified rotating disk electrode technique

Abstract

For the first time, the oxygen evolution reaction (OER) behavior of commercial catalyst-coated membranes (CCMs) has been studied using an in-house modified rotating disk electrode (MRDE) tip capable of reaching current densities of up to 2 A cm−2. The electrochemical results are comparable with a full PEM electrolysis cell. The kinetic analysis reveals Tafel slopes of about 50 and 60 mV dec−1 for all temperatures with the PEM electrolysis hardware and the MRDE, respectively. The activation energy of the OER obtained with the MRDE and the PEM electrolysis cell are 75 and 68 kJ mol−1, respectively. Detailed cyclic voltammetric measurements of Ir-based CCMs were performed to examine the influence of operating temperature, Ti-based current collectors, the scan rate on the adsorbed charge, and the electro kinetics of the OER. Six different expanded metal Ti current collectors were analyzed in sulfuric acid and their impact on the CCM charging at various temperatures were examined in order to calculate the electrode's inner and outer charge. It was observed that the voltammetric charge is proportional to the coverage of the CCM by the current collector. The MRDE tool presented here is an ideal tool for electrochemical characterization of CCMs and current collectors and allows for an economical and accelerated screening of these important PEM electrolyzer components without the requirement of full cell testing.