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Issue 4, 2017
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Mechanism and kinetics of the electrocatalytic reaction responsible for the high cost of hydrogen fuel cells

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Abstract

The sluggish oxygen reduction reaction (ORR) is a major impediment to the economic use of hydrogen fuel cells in transportation. In this work, we report the full ORR reaction mechanism for Pt(111) based on Quantum Mechanics (QM) based Reactive metadynamics (RμD) simulations including explicit water to obtain free energy reaction barriers at 298 K. The lowest energy pathway for 4 e water formation is: first, *OOH formation; second, *OOH reduction to H2O and O*; third, O* hydrolysis using surface water to produce two *OH and finally *OH hydration to water. Water formation is the rate-determining step (RDS) for potentials above 0.87 Volt, the normal operating range. Considering the Eley–Rideal (ER) mechanism involving protons from the solvent, we predict the free energy reaction barrier at 298 K for water formation to be 0.25 eV for an external potential below U = 0.87 V and 0.41 eV at U = 1.23 V, in good agreement with experimental values of 0.22 eV and 0.44 eV, respectively. With the mechanism now fully understood, we can use this now validated methodology to examine the changes upon alloying and surface modifications to increase the rate by reducing the barrier for water formation.

Graphical abstract: Mechanism and kinetics of the electrocatalytic reaction responsible for the high cost of hydrogen fuel cells

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Supplementary files

Article information


Submitted
24 Nov 2016
Accepted
20 Dec 2016
First published
21 Dec 2016

This article is Open Access

Phys. Chem. Chem. Phys., 2017,19, 2666-2673
Article type
Communication

Mechanism and kinetics of the electrocatalytic reaction responsible for the high cost of hydrogen fuel cells

T. Cheng, W. A. Goddard, Q. An, H. Xiao, B. Merinov and S. Morozov, Phys. Chem. Chem. Phys., 2017, 19, 2666
DOI: 10.1039/C6CP08055C

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