A Comprehensive Online Analytical System Coupled with Standardized Data Analysis for the Electrochemical Reduction of CO₂

The electrochemical reduction of CO₂ (CO₂RR) is a promising way to convert detrimental CO₂ emissions into sustainable fuels and chemicals, and thus to achieve a circular carbon economy_.¹ Depending on catalyst type and reaction conditions, different gaseous and liquid products can be obtained from the CO₂RR, and their production rates vary with reaction time. It becomes thus imperative, for any catalytic performance analysis, to be able to assess the product distribution online during CO₂RR_.^2,3 However, while gaseous products are readily analyzed online by gas chromatography, liquid products are typically only assessed at the end of the reaction due to the lack of suitable automated liquid sampling and analysis methods. In addition, reaction parameters such as CO₂ mass flow rates, temperatures and pressures are seldom recorded, causing the loss of significant information on catalysts, electrodes, and electrolyzers behavior.<br/>To overcome these issues, we assemble a comprehensive analytical system coupling online gas and liquid product analysis by gas and liquid chromatography leveraging a special automated liquid sampling valve with electrochemical protocols that assess CO₂RR performance, electrolyzer cell resistance and electrode surface area. In addition, we record CO₂ mass flow rates, electrolyzer temperatures, as well as gas and liquid flow pressures_.⁴ To rapidly and reproducibly handle the large and heterogeneous data volume obtained we implement a standardized data pipeline based on our own open-source software,⁵ which automatically parses the numerous different raw data files, composes a data set following FAIR practices,⁶ and post-processes and plots the data in a standardized way. We validate the analytical system by carrying out CO₂RR at 200 mA/cm² on Cu gas diffusion electrodes, following the changes in selectivity with reaction time for &gt; 10 gaseous and liquid products, and recording mass flow rates, electrolyzer temperatures and pressures. The modular nature of our analytical system, combined with the standardized data pipeline, allows us to freely increase the number and type of sensors used with minimal impact on the data analysis time, as well as to multiplex our analysis to 8 parallel electrolyzer cells, paving the way for a much deeper and faster understanding of the function of CO₂RR catalysts, electrodes, and electrolyzers.