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

Cheng, Tao and Goddard, William A., III and An, Qi and Xiao, Hai and Merinov, Boris and Morozov, Sergey I. (2017) Mechanism and kinetics of the electrocatalytic reaction responsible for the high cost of hydrogen fuel cells. Physical Chemistry Chemical Physics, 19 (4). pp. 2666-2673. ISSN 1463-9076. doi:10.1039/c6cp08055c.

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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 H_2O 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.

Item Type:Article
Related URLs:
URLURL TypeDescription information
Cheng, Tao0000-0003-4830-177X
Goddard, William A., III0000-0003-0097-5716
An, Qi0000-0003-4838-6232
Xiao, Hai0000-0001-9399-1584
Merinov, Boris0000-0002-2783-4262
Morozov, Sergey I.0000-0001-6226-5811
Additional Information:© 2017 the Owner Societies. Received 24th November 2016, Accepted 20th December 2016, First published online 21 Dec 2016. This work was supported by National Science Foundation (CBET 1512759, program manager Robert McCabe). We thank Dr Ted Yu for helpful discussions. Author contributions: T. C. and W. A. G. proposed the ideas; T. C., Q. A. and S. M. carried out the simulations; T. C. H. X. and B. M. analyzed the results, and the manuscript was written by T. C. and W. A. G. The authors declare no competing financial interests.
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Issue or Number:4
Record Number:CaltechAUTHORS:20170109-143914060
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:73344
Deposited By: Tony Diaz
Deposited On:10 Jan 2017 04:51
Last Modified:11 Nov 2021 05:15

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