Introduction of a Conductive Layer into Flood-Resistant Gas Diffusion Electrodes with Polymer Substrate for an Efficient Electrochemical CO₂ Reduction with Copper Oxide

Conversion of atmospheric carbon dioxide (CO 2 ) into valuable feedstocks is a crucial technology, and electrochemical reduction of CO 2 is a promising approach that can provide a useful source of ethylene (C 2 H 4 ). Gas diffusion electrodes (GDEs) placed at the interface of the CO 2 gas and electrolyte can achieve high current density through a sufficient supply of dissolved CO 2 to the reaction site, making them indispensable in industrial applications. However, conventional GDEs with carbon substrate have suffered from electrolyte flooding and consequent loss of efficiency, posing an obstacle for practical application. While flood-resistant GDEs with hydrophobic polymer substrate have been proposed recently, only conductive materials can be employed as electrocatalysts because of their insulative properties, despite the high activities of oxide materials such as copper oxide. Here, we introduce an aluminum conductive layer in GDE with polymer substrate to enable the use of electrically resistive catalysts. Cuprous oxide (Cu 2 O) with silver particles was tested as a model material and has shown prolonged stability (>17 h) with high C 2 H 4 Faraday efficiency (>50%) while suppressing flooding. A thorough characterization revealed that the conductive layer makes Cu 2 O an efficient electrocatalyst, even on the polymer substrate, by providing sufficient electrons through its conduction path. This research significantly expands the scope of electrode design by enabling the incorporation of a wide range of nonelectrically conductive materials on GDEs with polymer substrate.