title: Proton transfer dynamics control the mechanism of O2 reduction by a non-precious metal electrocatalyst.
abstract: Many chemical and biological processes involve the transfer of both protons and electrons. The complex mechanistic details of these proton-coupled electron transfer (PCET) reactions require independent control of both electron and proton transfer. In this report, we make use of lipid-modified electrodes to modulate proton transport to a Cu-based catalyst that facilitates the O2 reduction reaction (ORR), a PCET process important in fuel cells and O2 reduction enzymes. By quantitatively controlling the kinetics of proton transport to the catalyst, we demonstrate that undesired side products such as H2O2 and O2(-) arise from a mismatch between proton and electron transfer rates. Whereas fast proton kinetics induce H2O2 formation and sluggish proton flux produces O2(-), proton transfer rates commensurate with O-O bond breaking rates ensure that only the desired H2O product forms. This fundamental insight aids in the development of a comprehensive framework for understanding the ORR and PCET processes in general.
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Edmund C M
authors.identifier: 0000-0002-9313-1290
authors.initials: EC
authors.lastname: Tse
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Barile
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Kirchschlager
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: John P
authors.initials: JP
authors.lastname: Gewargis
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Steven C
authors.initials: SC
authors.lastname: Zimmerman
authors.affiliation: Manufacturing Systems Ltd., Auckland 0632, New Zealand.
authors.forename: Ali
authors.initials: A
authors.lastname: Hosseini
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.|International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka 819-0395, Japan.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Gewirth