Scale-Up of PTFE-Based Gas Diffusion Electrodes Using an Electrolyte-Integrated Polymer-Coated Current Collector Approach

Abstract

Nonconductive porous polymer substrates, such as PTFE, have been pivotal in the fabrication of stable and highperforming gas diffusion electrodes (GDEs) for the reduction of CO 2 / CO in small scale electrolyzers; however, the scale-up of polymer-based GDEs without performance penalties to technologically more relevant electrode sizes has remained elusive. This work reports on a new current collector concept that enables the scale-up of PTFE-based GDEs from 5 to 100 cm 2 and beyond. The present approach builds on a multifunctional current collector concept that enables multipoint frontcontacting of thin catalyst coatings, which mitigates performance losses even for high resistivity cathodes. Our improved current collector design concomitantly incorporates a flow-field functionality in a monopolar plate configuration, keeping electrolyte gaps small for increased performance. Experiments with 100 cm 2 cathodes were conducted in a one-gap alkaline AEM and acid CEM system. Our design represents an important step forward in the development of larger-size CO 2 electrolyzers.

Nonconductive Metal Oxide Gas Diffusion Layer for Mitigating Electrowetting during CO2 Electrolysis

“…These types have seen cases of durability in the time scale of 100+ h, , whereas in other instances, flooding started to compromise the stability of the product distribution in less than a few hours or only minutes of operation. ,, Carbon paper-based electrodes are porous and conductive but liable to electrowetting, ,,,, which was equally shown to be the case for the Vulcan carbon GDL in this work. The polymeric membrane has a much better hydrophobicity, but it lacks conductivity so that it often requires modification of the catalyst layer or a redesign of the electrolyzer. ,− Our system consisting of metal oxide GDL and Cu mesh has the advantage of mitigating the electrowetting in the GDL layer while at the same time enabling good conductivity through the catalyst layer via the Cu mesh. In addition, through annealing, it creates a firm adherence between the GDL and catalyst layer that prevents delamination throughout use.…”

“…Incorporating dielectric hydrophobic materials such as PTFE can be beneficial to retard the onset of electrowetting to higher voltages. ,− PTFE or polyvinylidene fluoride (PVDF) membranes have been employed as stand-alone GDL substrates, the most common candidate being known as expanded or sintered PTFE. ,− While they hinder the passage of water molecules from high hydrophobicity, however, these materials lack electrical conductivity. This places constraints on the loading of the catalyst and may require the addition of carbon black , or a tailored current collector plate design to ensure uniform current distribution.…”