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Solvent molecules form surface redox mediators in situ and cocatalyze O 2 reduction on Pd

Journal Article · · Science
 [1];  [2];  [1];  [1];  [3];  [2];  [1];  [2];  [3];  [2];  [1]
  1. Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, Champaign, IL 61801, USA.
  2. Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA.
  3. Department of Chemical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.

Solvent molecules influence the reactions of molecular hydrogen and oxygen on palladium nanoparticles. Organic solvents activate to form reactive surface intermediates that mediate oxygen reduction through pathways distinct from reactions in pure water. Kinetic measurements and ab initio quantum chemical calculations indicate that methanol and water cocatalyze oxygen reduction by facilitating proton-electron transfer reactions. Methanol generates hydroxymethyl intermediates on palladium surfaces that efficiently transfer protons and electrons to oxygen to form hydrogen peroxide and formaldehyde. Formaldehyde subsequently oxidizes hydrogen to regenerate hydroxymethyl. Water, on the other hand, heterolytically oxidizes hydrogen to produce hydronium ions and electrons that reduce oxygen. These findings suggest that reactions of solvent molecules at solid-liquid interfaces can generate redox mediators in situ and provide opportunities to substantially increase rates and selectivities for catalytic reactions.

Sponsoring Organization:
USDOE
Grant/Contract Number:
AC02-76SF00515
OSTI ID:
1765023
Journal Information:
Science, Journal Name: Science Journal Issue: 6529 Vol. 371; ISSN 0036-8075
Publisher:
American Association for the Advancement of Science (AAAS)Copyright Statement
Country of Publication:
United States
Language:
English

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