Elucidating the Origins of Electrocatalytic Phenomena using Steady State Isotopic Transient Kinetic Analysis
Research Poster Engineering 2025 Graduate ExhibitionPresentation by Abigail Circelli
Exhibition Number 49
Abstract
The intrinsic activity of an electrocatalyst is determined by the ratio of the coverage of reaction intermediates to their surface lifetimes at steady state. Unfortunately, no technique exists for measuring either of these critical activity parameters for electrocatalytic systems. However, they have both been measured for thermal heterogenous catalysts using steady state isotopic transient kinetic analysis (SSITKA). During SSITKA, the isotopic composition of the reactant is rapidly switched while the isotopic composition of the resulting products is monitored using a mass spectrometer. The observed product isotopic transients are directly related to the coverage and lifetime of the corresponding reaction intermediates. 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 sampled, identified, and quantified in real time. This presentation will demonstrate electrochemical SSITKA for the first time using DEMS and methanol (MeOH) oxidation over platinized Pt as a test reaction. The SSITKA measurements have been utilized to understand the rise and decline of the MeOH activity in the low overpotential regime. A direct correlation between the intrinsic activity calculated from activity parameters measured via the isotopic transients and the CO2 partial current density was observed, which validates the accuracy of the approach. The electrochemical SSITKA approach is general and can be applied to investigate any reaction that produces a volatile product. Thus, this analytical method will significantly accelerate our understanding of a variety of different electrocatalytic phenomena.
Importance
The intrinsic activity of an electrocatalyst is equivalent to the steady state coverage of reaction intermediates divided by their surface lifetimes. Therefore, electrocatalytic activity promotion occurs by either increasing the steady state coverage of reaction intermediates, reducing their surface lifetimes, or some combination of both. These parameters have been measured for thermal heterogenous catalytic reactions using steady state isotopic transient kinetic analysis (SSITKA). SSITKA measurements have never been performed for any electrocatalytic reaction due to the difficulty of aqueous media. The steady state surface coverages and lifetimes of electrochemical reaction intermediates have been quantified via eSSITKA for the first time. This technique can be used to investigate a variety of different electrocatalytic phenomena, such as cation-dependent reactions.