Quantification of CO and Further CO₂ Reduction Products by On‐line Mass Spectrometry

Abstract

The reduction of CO2 in water can yield a variety of volatile products mixed with the starting material and often dinitrogen as an inert gas. While mass spectrometry is ideally suited to the quantitative analysis of gases in low concentrations, the simultaneous detection is usually performed with a preliminary chromatographic separation. In its absence, the mass spectrometric signal at m/z=28 can be due to CO, CO2, and N2. Here, we demonstrate that ionizing the mixture of reaction products under 16 eV results in the selective detection of CO at m/z=28, at the complete exclusion of CO2 and N2. This method is applicable to headspace analysis after a bulk electrolysis and delivers product compositions as they depend on catalyst and applied potential. Furthermore, its immediate nature also enables the experimentalist to perform, in real time, a direct monitoring of the reaction products generated during cyclic voltammetry.

A brief review of in situ spectroscopic methods and electrochemical sensors as essential evaluation tools for the electrochemical reduction of CO2 (ElRC)

“…76,77 The electrochemicalmass spectrometry method can be used to quantify the reaction rate of the end product as well as identifying the reacting gases, intermediates and products with great sensitivity. 78 Further advancement in the method was investigated with the goal to detect the changes in the quantity of products with regard to time and electrode potentials, which was named differential electrochemical mass spectrometry (DEMS). 79 A hydrophobic membrane-enclosed electrochemical cell with an MS vacuum system makes up the electrochemical-mass spectrometry system.…”

“…8,9 In ElRC studies, numerous catalysts were utilized to generate a range of products by converting CO 2 , 80 and the product analysis was performed with a mass spectrometer. 75,78 The different products produced by ElRC pass through the membrane to the sample vaporization chamber in mass spectrometry, and the sample gets struck by an electron beam, which creates ion molecule/fragments of the original species in the ionization chamber. Then, the ions are passed through a mass analyser, which contains magnets, creating a magnetic eld and allowing the ions to be deected magnetically.…”

“…At different applied voltages, CO was mostly observed on the Au and Ag catalysts, H 2 on the Pt catalyst, and CH 4 , H 2 , and CO on the Cu catalyst. 78…”