Platinum surface oxides govern the cathodic overpotential of the oxygen reduction reaction
Artikel i vetenskaplig tidskrift, 2026
The oxygen reduction reaction (ORR) on platinum is limited by a substantial overpotential, which hampers the efficiency of fuel cell technologies. While adsorbate binding energies have been widely used to explain ORR kinetics, we here illustrate a more complex role of platinum surface oxides, which are often ambiguously defined in the literature. We use operando total reflection X-ray absorption fine structure spectroscopy (RefleXAFS), supported by X-ray photoelectron spectroscopy, density functional theory, and microkinetic modeling, to resolve the surface oxides on polycrystalline platinum and their impact on ORR. We identify the formation of a surface oxide as early as 1 VRHE in 0.1 M HClO4 and demonstrate that platinum spontaneously oxidizes at the open-circuit potential (OCP) under O2 saturation. Furthermore, we show that the oxide coverage increases with upper vertex potential, slower scan rates, and extended hold times at OCP, illustrating how oxides inhibit ORR during fuel cell start-up. Crucially, we demonstrate that the ORR onset is delayed until these oxides are reduced, establishing a direct, negative relationship between oxide coverage and ORR activity. This reveals a revised mechanism in which the potential-determining step is the reduction of surface oxides, and the slow kinetics of this restructuring ultimately determine when surface sites become catalytically available.
Författare
Alfred Larsson
Lunds universitet
Universiteit Leiden
Andrea Grespi
Lunds universitet
Ozbej Vodeb
Jozef Stefan Int Postgrad Sch
Universiteit Leiden
Kemijski Inštitut
Karen van den Akker
Universiteit Leiden
Auden Ti
Lunds universitet
Claire Berschauer
Lunds universitet
Alexandra M. Imre
Technische Universität Wien
Philip Miguel Kofoed
Malmö universitet
Estephania Lira
Lunds universitet
Mahesh Ramakrishnan
Lunds universitet
Stuart Ansell
Lunds universitet
Justus Just
Lunds universitet
Henrik Grönbeck
Chalmers, Fysik, Kemisk fysik
Ulrike Diebold
Technische Universität Wien
Edvin Lundgren
Lunds universitet
Lindsay R. Merte
Malmö universitet
Dusan Strmcnik
Kemijski Inštitut
Rik Mom
Universiteit Leiden
Marc T. M. Koper
Universiteit Leiden
EES CATALYSIS
2753-801X (eISSN)
Vol. In PressÄmneskategorier (SSIF 2025)
Materialkemi
Oorganisk kemi
Fysikalisk kemi
DOI
10.1039/d6ey00014b
PubMed
41858921