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

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.