(678d) Electrochemical Steady State Isotopic Transient Kinetic Analysis (eSSITKA): A New Technique for the Evaluation of Electrocatalytic Materials

Electrocatalysis enables chemical transformations to be directly driven by renewable electricity, providing a viable route toward the decarbonization of the chemical industry. The implementation of electrocatalytic technologies relies on the development of electrocatalysts with high intrinsic activity. Intrinsic activity is the product of the steady state surface coverage of reaction intermediates and their surface lifetimes. Unfortunately, no method currently exists for measuring either of these critical parameters. However, these parameters are routinely measured in thermal catalytic science using steady state isotopic transient kinetic analysis (SSITKA). SSITKA involves reaching steady state in a catalytic reactor and then rapidly changing the isotopic composition of the reacting species. The catalyst surface is covered by reaction intermediates derived from the initial reactant at the moment of this isotopic switch. The steady state surface coverage of these intermediates is measured by quantifying the total number of product molecules evolved from the catalyst surface with the initial reactant isotopic composition after the switch has been performed. Additionally, their surface lifetimes are quantified by fitting the decaying rate of formation of these products to an exponential function. While SSITKA has been performed for thermal catalytic systems for decades, it has never been applied to electrocatalytic systems until now. Differential electrochemical mass spectrometry (DEMS) is an analytical technique that interfaces an electrochemical reactor to a mass spectrometer using a pervaporation membrane. This configuration enables volatile electrochemical reaction products to be continuously collected, identified, and quantified in real time. Coating the electrocatalyst directly onto the pervaporation membrane increases both the product collection efficiency and time response. This presentation will describe our efforts to perform electrochemical SSITKA (eSSITKA) for the first time. The insights obtained using this technique will be leveraged to explain the origins of many electrocatalytic phenomonon, such as the cation dependent activity of electrochemical CO₂ reduction.