Zeolite modifications to the cathode catalyst layer to enable stable and selective CO2 electrolysis towards multi-carbon products.

• Dante Paparella, Chemical Engineering, University of Delaware

• Izak Minnie, Chemical and Biomolecular Engineering, University of Delaware

Copper (Cu)-based catalysts are very promising for electrochemical CO₂ reduction, due to their ability to produce valuable multicarbon (C₂₊) products, such as ethanol and ethylene; however, the lack of sufficient stability and selectivity means it is not yet commercially viable. To address these issues, the catalyst layer of the cathode gas diffusion electrode has been modified using zeolites due to their tunable porosity, hydrophobicity, and long history of use in thermocatalytic applications. For this work, we consider two zeolite frameworks: MFI and LTA. For the MFI zeolite, the silica to alumina ratio (SAR) was varied from 40-360 to test the effect of zeolite hydrophobicity. The LTA with a SAR of 1 was used to study the effect of zeolite addition method on performance. We compare mixing zeolites into the catalyst layer precursor ink with electrochemical growth of zeolites on the sprayed catalyst layer. The performance of the zeolite GDEs were tested in a 5cm² zero-gap electrochemical cell at current densities between 50 and 250 mA/cm². Both tests showed that zeolite addition adds stability in the cell potential but also promotes the undesirable hydrogen evolution reaction (HER). Higher MFI SAR was found to increase ethylene production, indicating that higher hydrophobicity favors multicarbon products. Electrochemically growing LTA zeolites onto the cathode promotes a lot more hydrogen production and reduces ethylene production, compared to LTA sprayed, indicating a change in the catalyst’s active environment. These results show that although zeolites show promise for increasing stability in the system, product selectivity still remains a challenge.