Design and Diagnosis of high-performance CO2-to-CO electrolyzer cells

04 January 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


This work reports the design of a highly efficient neutral-pH CO2-to-CO zero-gap electrolyzer incorporating a new family of 2D layered framework-derived mesoporous single atom NiNC catalysts. What sets its performance apart from previous reports is not only the ~100% CO faradaic efficiency at applied current densities of up to 300 mA cm-2 at just above 3 V cell voltage and 40% total energy efficiency, but the uniquely low stoichiometric CO2 excess, stoich, of 1.2 that yields a molar CO concentration of around 70%Vol in the electrolyzer exit stream at 40% single pass CO2 conversion. This CO-rich exit stream and the low cost catalyst makes this electrolyze design ideally suited for cost-effective and energy efficient tandem cell configurations for high C2+ product yields. We also propose and validate a new kinetic diagnostic tool to help resolve mechanisms of undesired CO2 loss. We introduce an experimentally accessible carbon crossover coefficient, CCC, that describes the ratio between non-catalytic acid-base CO2 consumption and catalytically generated alkalinity. It offers an intuitive insight into the nature of the prevalent ionic transport. Combined with the stoich and the faradaic CO efficiency data, the CCC analysis offers practical guidelines toward improved electrolyzer designs. Our CCC-based cell diagnosis can be applied more broadly to all CO2 electrolyzers


CO2 reduction
NiNC catalyst

Supplementary materials

Supporting Information
Additional graphics, tables and explanatory text to prove and support our statements.


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