Quantitative DEMS analysis of CO2 evolution reactions in alkaline electrolyte solutions

Abstract

CO₂ evolution is involved in various main and side reactions of electrochemical systems, such as carbon corrosion reactions and alcohol oxidation reactions. Differential electrochemical mass spectroscopy (DEMS) has been intensively applied to analyze the partial current of the CO₂ evolution reaction in acidic and neutral electrolyte solutions. However, the quantitative analysis of the CO₂ evolution reaction in alkaline electrolyte solutions has not been successful when catalyst-loaded carbon electrodes were applied, due to the high solubility of CO₂ in the electrolyte. In this study, we develop a new DEMS system combining microreactor and ion exchange membrane to quantitatively analyze CO₂ evolution reactions of catalyst-loaded carbon electrodes in alkaline electrolyte solutions. The calibration constant, which correlates the mass signal of m/z = 44 to the partial current of the CO₂ evolution reaction, is successfully obtained from the Faradaic current and the mass signal of CO stripping voltammetry. We analyze carbon corrosion reactions of Pt and metal oxide-loaded carbon electrodes to demonstrate the effectiveness of the constructed system. The corrosion behavior of the Pt-loaded carbon is similar to that in the acidic electrolytes except for the onset potential of the carbon corrosion. La_0.6Ca_0.4CoO₃ and Ca₂FeCoO₅ show electrochemical carbon corrosion activity, while La_0.4Sr_0.6MnO₃ does not show distinct electrochemical carbon corrosion activity.