On the electro-oxidation of small organic molecules: towards a fuel cell catalyst testing platform with realistic reaction environment

Abstract

The electrocatalytic oxidation of small organic compounds such as methanol or formic acid has been the subject of numerous investigations in the last decades. The motivation for these studies is often their use as fuel in so-called direct methanol or direct formic acid fuel cells, promising alternatives to hydrogen-fueled proton exchange membrane fuel cells. The fundamental research spans from screening studies to identify the best performing catalyst materials to detailed mechanistic investigations of the reaction pathway. These investigations are commonly performed in standard three electrode electrochemical cells with a liquid supporting electrolyte to which the methanol or formic acid is added. In fuel cell devices, however, no liquid electrolyte will be present, instead membrane electrolytes are used. The question therefore arises, to which extend results from conventional electrochemical cells can be extrapolated to conditions found in fuel cells. We previously developed a gas diffusion electrode setup to mimic "real-life" reaction conditions and study electrocatalysts for oxygen gas reduction or water splitting. It is here demonstrated that the setup is also suitable to investigate the properties of catalysts for the electro-oxidation of small organic molecules. 2Using the gas diffusion electrode setup, it is seen that employing a catalyst -membrane electrolyte interface as compared to conventional electrochemical cells can lead to significantly different catalyst performances. Therefore, it is recommended to implement gas diffusion electrode setups for the investigation of the electro-oxidation of small organic molecules.

The gas diffusion electrode setup as a testing platform for evaluating fuel cell catalysts: A comparative RDE‐GDE study

“…Therefore, it can be argued that the shift in the CO stripping peak is related to a reduced anion blocking in the GDE membrane-catalyst environment. [32] Interestingly, the peak position observed in the CO stripping curve recorded in the GDE setup is similar to the one observed in an MEA measurement by Harzer et al, [33] although it needs to be stressed out that a direct comparison is difficult due to the different catalyst and different experimental parameters such as scan rate and temperature. In addition, the CO stripping shows a smaller ECSA for the catalyst layer in the GDE setup compared with the RDE setup, which is consistent with the observation in the H upd region, that is, the overall peak area in the H upd region in GDE measurement is smaller than the one from RDE measurement.…”

The Gas diffusion electrode setup as a testing platform for evaluating fuel cell catalysts: a comparative RDE-GDE study

“…Therefore it can be argued that the shift in the CO stripping peak is related to a reduced anion blocking in the GDE membrane-catalyst environment [25]. Interestingly, the peak position observed in the CO stripping curve recorded in the GDE setup is similar to the one observed in an MEA measurement by Harzer et al [26], although it needs to be stressed out that a direct comparison is difficult due to the different catalyst and different experimental parameters such as scan rate and temperature.…”