Using Complex Collection Efficiency for Detection of Oxidation Products – Examples from Hydrogen Evolution, Oxygen Evolution and CO2 Reduction

Abstract

Electrochemical reactions can often yield a distribution of products, for example for CO2 reduction on Cu and methanol oxidation on Pt. This distribution varies with (over)potential and catalyst type, and usually requires the experimenter to incorporate detectors such as mass spectrometry or gas chromatography into their experimental setup. Electrochemical methods also exist, such as using the rotating ring-disk electrode or the analogous double channel electrodes. However, these methods suffer from unsteady measurements, and are hard to do with the desired accuracy. Techniques using alternating current perturbations may be an improvement here and preliminary work on transfer functions for product detection show promise, here called complex collection efficiency (CCE)[1]. This technique has the advantage that it reduces or removes the influence of parasitic currents on the electrodes and can yield the product distribution as a function of current density and/or electrode potential. In this work, CCE was tested on a lab made microfluidic system with double channel electrodes and measurements were done on ideal reactions with a single product, the hydrogen evolution reaction and oxygen evolution reaction to optimize and calibrate the setup, see Figure 1. Finally, CO2 reduction on Ag was attempted and compared with literature values as this primarily yields CO and H2 as the reaction products. Holm, T., J.A. Diaz Real, and W. Mérida, Numerical modeling of complex collection efficiency for double channel electrodes. Journal of Electroanalytical Chemistry, 2019. 842: p. 115-126. Figure 1