Through‐Plane Conductive Hydrophobic Electrodes for CO ₂ Electrolysis to Ethylene

ABSTRACT Copper catalyst gas diffusion electrodes (GDEs) have demonstrated unique electrochemical selectivity converting CO ₂ to C ₂ ‐hydrocarbons such as ethylene and ethanol but have been challenged by their hydrophobic chemical stability and internal electrical resistance leading to low energy efficiency. Carbon‐supported GDEs have low electrical resistance but lack sufficient stability at industrially relevant current densities. While polymer‐supported GDEs have improved hydrophobicity, they also display high in‐plane electrical resistance, particularly at industrial scales. In this work, we demonstrate a composite gas diffusion layer that combines hydrophobic porous polymers with an electrically conductive backbone addressing these core gas diffusion electrode (GDE) scaling challenges. We investigate the material properties of standalone porous perfluoropolyether (PFPE) polymers, including porosity and surface morphology, under varying processing conditions and then incorporate these polymers into a porous copper foam. This composite enhances the mechanical rigidity necessary for cell assembly and provides a through‐plane electrical conduction path to reduce electrical resistive losses. This enhanced PFPE composite GDE displays efficient CO ₂ reduction, achieving 15% ethylene energy efficiency at 100 cm ² . These findings contribute to the development of advanced catalyst materials and electrode architectures and promote scalable strategies for electrochemical conversion of CO ₂ into high‐value carbon products.