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Effect of pH on the activity of platinum group metal-free catalysts in oxygen reduction reaction

Rojas-Carbonell, Santiago; Artyushkova, Kateryna; Serov, Alexey; Matanovic, Ivana; Atanassov, Plamen; Santoro, Carlo


Santiago Rojas-Carbonell

Kateryna Artyushkova

Alexey Serov

Ivana Matanovic

Plamen Atanassov

Carlo Santoro


© 2018 American Chemical Society. The impact of the electrolyte's pH on the catalytic activity of platinum group metal-free (PGM-free) catalysts toward the oxygen reduction reaction (ORR) was studied. The results indicate that the ORR mechanism is determined by the affinity of protons and hydroxyls toward multiple functional groups present on the surface of the PGM-free catalyst. It was shown that the ORR is limited by the proton-coupled electron transfer at pH values below 10.5. At higher pH values (>10.5), the reaction occurs in the outer Helmholtz plane (OHP), favoring hydrogen peroxide production. Using a novel approach, the changes in the surface chemistry of PGM-free catalyst in a full pH range were studied by X-ray photoelectron spectroscopy (XPS). The variations in the surface concentration of nitrogen and carbon species are correlated with the electron transfer process and overall kinetics. This study establishes the critical role of the multitude of surface functional groups, presented as moieties or defects in the carbonaceous "backbone" of the catalyst, in mechanism of oxygen reduction reaction. Understanding the pH-dependent mechanism of ORR provides the basis for rational design of PGM-free catalysts for operation across pH ranges or at a specific pH of interest. This investigation also provides the guidelines for developing and selecting ionomers used as "locally-confined electrolytes", by taking into account affinities and possible interactions of specific functional groups of the PGM-free catalysts with protons or hydroxyls facilitating the overall ORR kinetics.


Atanassov, P., Matanovic, I., Serov, A., Artyushkova, K., Rojas-Carbonell, S., & Santoro, C. (2018). Effect of pH on the activity of platinum group metal-free catalysts in oxygen reduction reaction. ACS Catalysis, 8(4), 3041-3053.

Journal Article Type Article
Acceptance Date Mar 1, 2018
Publication Date Mar 1, 2018
Deposit Date May 4, 2018
Journal ACS Catalysis
Electronic ISSN 2155-5435
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 8
Issue 4
Pages 3041-3053
Keywords oxygen reduction reaction, PGM-free catalysts, pH-dependent activity, XPS, mechanism
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