Pressure and bias dependence of the rate-limiting steps of the oxygen reduction reaction.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41390836.
- Also identified by DOI 10.1038/s41467-025-67494-x and PMC identifier 12708627.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The oxygen reduction reaction limits the energy efficiency of H<sub>2</sub> fuel cells and Li-air batteries, yet, it remains poorly understood within popular kinetic frameworks. Here, we study the oxygen reduction reaction on Pt/C, Ir/C, Ru/C and Rh/C nanoparticles as a function of electrochemical bias, temperature and O<sub>2</sub> pressure at industrially-relevant conditions in membrane electrode assemblies. Bias-, and pressure-dependent Arrhenius analysis reveals distinct changes in the (apparent) activation energy and pre-exponential factor that we relate to kinetics that cascade through a series of rate-limiting steps and transition states. Further, while the kinetics are accelerated by the pressure and bias, they remain pinned to pseudo-capacitive reduction processes and structural changes at the water-solid interface. Collectively, our study informs on how the free energy driving force and pressure tune the degree of rate control of rate-limiting steps and transition states of (electro)catalytic multi-step reactions and how this is related to structural and chemical changes at the interface. This is at the very heart of catalysis.