Electrochemical CO₂ reduction to chemicals and fuels is a promising strategy to mitigate the ever-increasing carbon emission. The industrial application of CO₂ electrolysis requires the electrolyzers to be operated at a high reaction rate, energy efficiency, and sufficient long-term stability. In the past, CO₂ electrochemical reduction has focused on improving Faradaic efficiency and productivity in the past decades. For example, the Faradaic efficiency of CO₂ to C₂H₄ conversion has reached 70% at a current density beyond 1 A cm^-2. However, CO₂ reduction long-term stability still faces multiple challenges. Flooding of gas diffusion layer (GDL) is among several crucial stability issues which block the CO₂ transport pathway, thus resulting in low CO₂ availability in the catalyst layer (CL). Specifically, regular GDLs suffer from low water breakthrough pressure, degrading hydrophobicity, and electro-osmosis. Some strategies have emerged to counter the flooding issue. For example, PTFE membranes with micropores were designed to replace regular carbon paper. The PTFE membrane is super-hydrophobic and chemically inert, which relieves the water breakthrough pressure and mitigates the hydrophobicity degradation. However, the PTFE membrane is non-conductive, thus imposing challenges for large-scale applications. In this work, we have designed a water management GDL, combining the advantages of regular carbon paper and PTFE membrane. This GDL comprises a PTFE microporous layer (MPL) for water management and a carbon fiber network for electron conduction. The PTFE MPL and carbon fiber network are compressed into one single layer. Using this design, the CO₂ to C₂H₄ selectivity achieves over 50% at -0.66 V vs. RHE under current density beyond 300 mA cm^-2. These results demonstrate the excellent gas transport efficiency and stability of the water management GDL, which can significantly facilitate the development of large-scale CO₂ electrochemical conversion.

Acknowledgment: The project is financially supported by the Department of Energy’s Office of EERE under the Grant DE-EE000942l