Oxygen Hydration Mechanism for the Oxygen Reduction Reaction at Pt and Pd Fuel Cell Catalysts
Abstract
We report the reaction pathways and barriers for the oxygen reduction reaction (ORR) on platinum, both for gas phase and in solution, based on quantum mechanics calculations (PBE-DFT) on semi-infinite slabs. We find a new mechanism in solution: O_2 → 2O_(ad) (E_(act) = 0.00 eV), O_(ad) + H_2O_(ad) → 2OH_(ad) (E_(act) = 0.50 eV), OH_(ad) + H_(ad) → H_2O_(ad) (E_(act) = 0.24 eV), in which OH_(ad) is formed by the hydration of surface O_(ad). For the gas phase (hydrophilic phase of Nafion), we find that the favored step for activation of the O_2 is H_(ad) + O_(2ad) → HOO_(ad) (E_(act) = 0.30 eV) → HO_(ad) + O_(ad) (E_(act) = 0.12 eV) followed by O_(ad) + H_2O_(ad) → 2OH_(ad) (E_(act) = 0.23 eV), OH_(ad) + H_(ad) → H_2O_(ad) (E_(act) = 0.14 eV). This suggests that to improve the efficiency of ORR catalysts, we should focus on decreasing the barrier for Oad hydration while providing hydrophobic conditions for the OH and H_2O formation steps.
Additional Information
© 2011 American Chemical Society. Published: February 24, 2011. Received: December 31, 2010. Accepted: February 08, 2011. This research was supported partially with funding from the Ford Motor Company and from the DOE (DE-AC02-06CH11357). We thank Dr. Gerald Voecks for helpful discussions.Attached Files
Supplemental Material - jz101753e_si_001.pdf
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Additional details
- Eprint ID
- 23419
- DOI
- 10.1021/jz101753e
- Resolver ID
- CaltechAUTHORS:20110421-152529609
- Ford Motor Company
- DE-AC02-06CH11357
- Department of Energy (DOE)
- Created
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2011-04-22Created from EPrint's datestamp field
- Updated
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2021-11-09Created from EPrint's last_modified field