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Disentangling multistep kinetics by combining electrochemical Arrhenius analysis with micro-kinetic modelling
Mathieu Lizée1, Alex Ricardo Silva Olaya1, Jody Druce1
1Fritz Haber Institute of the Max Planck Society, Berlin, Germany. lizee@fhi-berlin.mpg.de.
Faraday Discussions
|May 5, 2026
Summary
Temperature-dependent electrochemistry reveals complex kinetics in electrocatalytic reactions. A two-step model explains how electrochemical bias influences activation parameters and identifies rate-determining steps for reactions like oxygen reduction.
Area of Science:
- Electrochemistry
- Chemical Kinetics
- Materials Science
Background:
- Electrocatalytic reaction mechanisms are complex due to multiple steps, intermediates, and dynamic catalyst changes.
- Traditional single-step theories like Butler-Volmer fail to explain observed bias-dependent activation parameters in many reactions.
- Temperature-dependent electrochemistry offers a powerful tool to probe reaction kinetics and activation energies.
Purpose of the Study:
- To investigate the overpotential-dependent activation parameters of a two-step microkinetic model.
- To understand how electrochemical bias influences kinetic regimes and rate control in electrocatalysis.
- To apply the model to experimental data for the oxygen reduction reaction.
Main Methods:
- Development and analysis of a two-step microkinetic model (electrochemical adsorption followed by chemical recombination).
- Utilizing temperature-dependent electrochemistry to extract apparent activation energy and pre-exponential factor as a function of electrochemical bias.
- Fitting the model to experimental data for the oxygen reduction reaction on Pt and Ru nanoparticles.
Main Results:
- The electrochemical bias drives transitions across distinct kinetic regimes with varying rate control.
- Bias-dependent Arrhenius signatures constrain the binding and activation enthalpies of reaction intermediates.
- For oxygen reduction reaction, one intermediate and two partially rate-determining steps control kinetics over a wide overpotential range on Pt and Ru nanoparticles.
- Extracted binding/activation energies and bias-dependent coverages.
Conclusions:
- Minimalistic microkinetic models combined with temperature-dependent electrochemistry provide mechanistic insights.
- This approach allows direct comparison with theoretical calculations (e.g., DFT) and operando spectroscopy.
- The study elucidates the complex kinetics of electrocatalytic reactions, offering a pathway for catalyst optimization.
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