The Kitchin Research Group

In our recent work published in the Journal of the American Chemical Society, we investigated how electrolyte pH affects the oxygen reduction reaction (ORR) - a critical process in fuel cells and batteries. Working with an outstanding team including Jay Bender, Rohan Sanspeur, and colleagues from UT Austin, we tackled a long-standing puzzle: why does changing pH dramatically affect ORR rates on some catalysts (like Au) but barely affect others (like Pt)?

Through careful electrochemical experiments, we measured ORR activity across different metals in both acidic and alkaline conditions. The results were striking - Au catalysts showed dramatically increased activity when moving from acid to base, while Pt remained essentially unchanged. Our kinetic analysis revealed that the rate-determining steps don't actually change with pH, challenging previous explanations.

The breakthrough came from combining these experiments with density functional theory (DFT) calculations. We discovered that electric field effects provide a unifying explanation. When pH increases, the interfacial electric field becomes more negative. This field change strongly stabilizes the key reaction intermediate (*O₂) on weakly binding metals like Au, dramatically lowering activation barriers. On strongly binding metals like Pt, the reaction intermediates are much less sensitive to electric fields, explaining their pH-independent behavior.

This computational insight allowed us to extend our understanding to other metals (Ag, Ir, Ru, Pd), confirming the general principle: pH effects depend on how field-sensitive the rate-determining intermediates are.

Our work demonstrates the power of combining rigorous experimental kinetics with advanced computational modeling. By understanding these fundamental electric field effects, we can now predict and potentially engineer pH-dependent catalytic behavior - opening new avenues for optimizing electrochemical energy conversion devices.

@article{bender-2025-how-elect,
  author = {Jay T. Bender and Rohan Yuri Sanspeur and Nicolas Bueno Ponce and Angel E. Valles and Alyssa K. Uvodich and Delia J. Milliron and John R. Kitchin and Joaquin Resasco},
  title = {How Electrolyte Ph Affects the Oxygen Reduction Reaction},
  journal = {Journal of the American Chemical Society},
  volume = {nil},
  number = {nil},
  pages = {jacs.5c14208},
  year = {2025},
  doi = {10.1021/jacs.5c14208},
  url = {http://dx.doi.org/10.1021/jacs.5c14208},
  DATE_ADDED = {Thu Oct 2 07:22:51 2025},
}

Copyright (C) 2025 by John Kitchin. See the License for information about copying.

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