Application of Selected-Ion-Flow-Tube Mass Spectrometry For Real-Time Operando Quantitative Measurement of Product Formation for Electrochemical Reduction of Carbon Dioxide

Abstract

Electrochemical CO2 reduction reaction (CO2R) is a promising route to help reduce greenhouse gas emissions and reach carbon dioxide net zero emissions to combat global warming. Currently, in order to investigate catalytically produced products from CO2R offline methods such as gas chromatography (GC) and nuclear magnetic resonance (NMR) are used. These offline methods have a time resolution on the minutes to hours scale which leads to uncertainty of evaluating how products are produced from CO2R, such as knowing if a product is produced from electrochemical means or chemical conversion, and if a product is being produced in a linear rate of production or a different rate. This is where the ability to have real-time analysis of the products generated from CO2R is desirable, as it can more definitively answer many of these questions. Yet few analytical techniques have been developed in detail so far to achieve real-time analysis. Herein, we show the use of selected-ion flow-tube mass spectrometry (SIFT-MS) that quantitatively measures in realtime an array of 10 C1, C2, and C3 products from CO2R such as ethanol, ethylene or methane. The custom-developed SIFT-MS selected ion mode scan measures the concentration of gas and liquid-phase products of CO2R at the same time and is compatible with any electrolyzer cell. We demonstrate that the SIFT-MS technique can reliably and accurately determine product concentration in real-time through the evaluation of Cu foil and its comparison to traditional techniques. Considering the narrow range of developed and deployed techniques for real-time quantitative product analysis for CO2R, this study on SIFT-MS is a critical tool for future research in accelerating and optimizing catalyst design for electrochemical CO2R applications.