Insights into selectivity variations during CO2 and CO reduction on CuZn-based Gas Diffusion Electrodes

Federica Zammillo^a^,^b, Enggar Wibowo^c, Flora Haun^c, Eleonora Calì^a, Hilmar Guzmán^a, Siddhart Gupta^c, Federico Dattila^a, Giulia Cuatto^a, Gumaa El-Nagar^c, Matthew T. Mayer^c, Simelys Hernández^a

^aDepartment of Applied Science and Technology (DISAT), Politecnico di Torino, C.so Duca degli Abruzzi, 24, 10129, Turin, Italy.

^bLarge-Scale Energy Storage Section, Process & Energy Department, Faculty of Mechanical Engineering, Delft University of Technology, Leeghwaterstraat 39, Delft 2628 CB, The Netherlands

^cElectrochemical Conversion, Helmholtz-Zentrum Berlin für Materialen und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany

Proceedings of MATSUS Fall 2026 Conference (MATSUSFall26)

E4 Advances and Innovations in (Photo)Electrochemical CO2 and N2 Conversion and Water Splitting

Palma, Spain, 2026 October 26th - 30th

Organizer: Guillermo Díaz-Sainz

Poster, Federica Zammillo, 320
Publication date: 22nd July 2026

The electrochemical reduction of carbon dioxide (CO₂) offers an incredible opportunity to capture and store CO₂ and renewable energy in valuable platform chemicals and fuels, driving the transition from fossil fuels to sustainable energy sources.¹ Growing interest is being directed toward decoupling the reaction into stepwise processes: CO₂-to-carbon monoxide (CO) conversion followed by CO-to-C₂₊products to boost CO availability at active sites. Moreover, compared to the parent CO₂ reduction reaction (CO₂R), CO reduction (COR) is not affected by the (bi)carbonate issue and is thereby compatible with the highly alkaline media, reported to help C₂₊ product selectivity.²

Bimetallic Cu-Zn materials have been extensively studied for their ability to facilitate the formation and stabilization of polarized Cu^δ+ species, which are critical for facilitating C-C coupling.³ In this work, we investigated the selectivity variations that arise from CO₂ and CO reduction in catholyte-flow and zero-gap electrolyzers using CuZn-based gas diffusion electrodes.⁴ The presence of zinc appears to promote selectivity towards ethanol, compared to ethylene production, as demonstrated by the results obtained from control experiments on copper oxide. Under CO₂ reduction conditions in the catholyte flow cell, we demonstrated that the catalyst pre-reduction leads to a marked change in selectivity at 100 mA cm^-2, with ethanol becoming the dominant CO₂R product. Interestingly, when switching to pure CO, a remarkable Faradaic Efficiency of approximately 70% toward C₂ products was achieved at an average cathodic potential of -2.1 V vs Ag/AgCl. The stability of the system at 100 mA cm^-2 was evaluated over approximately three hours, during which a constant FE_C2H4 of 35% was demonstrated. Operando X-ray absorption spectroscopy measurements in fluorescence mode were conducted at the BESSY II synchrotron to uncover the cause of the superior activity toward C₂ on bimetallic Cu-Zn materials, using a zero-gap cell that mimics the ex-situ cell employed for laboratory data. Our investigation highlights the importance of considering multiple factors to accelerate the practical application of the CuZn bimetallic systems at a larger scale.

References:

[1] Stephens, I. E. L. et al. 2022 roadmap on low temperature electrochemical CO2 reduction. JPhys Energy (2022)

[2] Ding, X., Zhang, J. & Li, Y. CO electroreduction: What can we learn from its parent reaction, CO2 electroreduction? eScience (2023)

[3] Jeon, H. S. et al. Operando insight into the correlation between the structure and composition of CuZn nanoparticles and their selectivity for the electrochemical CO2 reduction. J. Am. Chem. Soc. 141, 19879–19887 (2019)

[4] 1. Stephens, I. E. L. et al. 2022 roadmap on low temperature electrochemical CO2 reduction. JPhys Energy (2022) doi:10.1088/2515-7655/ac7823. 2. Ding, X., Zhang, J. & Li, Y. CO electroreduction: What can we learn from its parent reaction, CO2 electroreduction? eScience (2023) doi:10.1016/j.esci.2023.100137. 3. Jeon, H. S. et al. Operando insight into the correlation between the structure and composition of CuZn nanoparticles and their selectivity for the electrochemical CO2 reduction. J. Am. Chem. Soc. 141, 19879–19887 (2019). 4. Guzmán, H. et al. CuZnAl-oxide nanopyramidal mesoporous materials for the electrocatalytic CO2 reduction to syngas: Tuning of H2/CO ratio. Nanomaterials (2021)

Acknowledgements:

The financial support of the SunCoChem project (Grant Agreement No 862192) and the FlowPhotoChem project (Grant Agreement No 862453) of the European Union’s Horizon 2020 Research and Innovation Action programme is acknowledged. The authors acknowledge funding from the project PNRR – Partenariati estesi – “NEST – Network 4 Energy Sustainable Transition”. We also thank HZB for experimental access at the KMC-2 beamline, including support from Dr. Götz Schuck. The Foundation Blanceflor Boncompagni Ludovisi is acknowledged for supporting research mobility.

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