(589d) Transient Kinetic Isotope Effects Reveal Interfacial CO2 Dissolution Kinetics

The formation of carbonate and the associated energy losses are one of the main challenges for the economically viable reduction of CO₂. It is well-known that the kinetics and thermodynamics of the formation of carbonate as well as the electrocatalytic reduction of CO₂ itself are highly pH sensitive. Measuring the interfacial pH at the electrode is not trivial due to convoluting effects of mass transport and the consumption of protons due to CO₂ reduction and the parasitic hydrogen evolution reaction. Most previously reported approaches offer insights only to a limited extent or on model catalysts. Here, we report the use of transient kinetic measurements with isotopically labeled CO₂ by Differential Electrochemical Mass Spectrometry on various gas diffusion electrodes. By both measuring the steady state absorption of CO₂ into the electrolyte in the microporous layer as well as the transient decay curve, we are able to determine the rates of carbonate formation as well as interfacial pH accurately. This approach works for most gas diffusion electrode materials and is sensitive to applied potential as well as current densities.