Hierarchically Conductive Electrodes Unlock Stable and Scalable CO2 Electrolysis

Electrochemical CO2 reduction has emerged as a promising CO2 utilization technology, with Gas Diffusion Electrodes (GDEs) becoming the predominant architecture to maximize performance. GDEs must maintain robust hydrophobicity to prevent flooding, while also ensuring high conductivity to minimize ohmic losses. Intrinsic material tradeoffs have led to two main GDE architectures: carbon paper is highly conductive but floods easily; ePTFE is flooding resistant but non-conductive, limiting electrode sizes to just 5cm2. Here we demonstrate a Hierarchically Conductive GDE architecture (HCGDE) which overcomes these limitations by employing inter-woven microscale conductors within a hydrophobic ePTFE membrane. We develop a model which captures the spatial variability in voltage and product distribution on electrodes due to ohmic losses and use it to rationally design the HCGDE. The HCGDE architecture overcomes scaling limitations, achieving C2+ Faradaic efficiencies of ~75% for electrodes as large as 50cm2. Our approach can be broadly applied to scale any electrode, independent of catalyst chemistry and morphology.