| Popis: |
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 |
