(134b) Investigation of Ammonia Oxidation On the Platinum Surface for Hydrogen Generation

The feasibility of using hydrogen as an energy source is often dependent on in situ generation due to storage issues. One of the methods considered for hydrogen generation at the point of use is ammonia electrolysis[1], with hydrogen produced at the cathode and nitrogen produced at the anode. Thus, this electrolytic process is a combined waste-remediation and energy-generation technology. Currently, the slow reaction at the anode and the deactivation of the platinum catalyst over time is an item for potential improvement. Consequently, this project will focus on the thermodynamics of the oxidation of ammonia to nitrogen at the anode.
Researchers have suggested two possible mechanisms[2, 3] with intermediates such as NH₂, NH and N (Oswin and Salomon) as well as N₂H₄, N₂H₃, N₂H₂ and N₂H (Gerischer, Gerischer and Mauerer) expected on the catalytic surface during this conversion of ammonia to nitrogen.

Using Gaussian 09[4], calculations have been performed on the interaction of these intermediates with platinum clusters. These calculations have predicted the geometric, electronic and vibrational characteristics of the systems. Initial results have shown valid agreement with experimentally measured adsorption energies and vibrational frequencies for smaller molecules like NH_x (x = 0 - 3) and OH_y (y = 1&2) molecules [5]. Further results will be presented at the meeting.

References

[1] F. Vitse, M. Cooper, and G. G. Botte, "On the use of ammonia electrolysis for hydrogen production," Journal of Power Sources, vol. 142, pp. 18-26, 2005.

[2] H. G. Oswin and M. Salomon, "The Anodic Oxidation of Ammonia at Platinum Black Electrodes in Aqueous KOH Electrolyte," Canadian Journal of Chemistry, vol. 41, pp. 1686-1694, 1963.

[3] H. Gerischer and A. Mauerer, "Untersuchungen Zur anodischen Oxidation von Ammoniak an Platin-Elektroden," Journal of Electroanalytical Chemistry, vol. 25, pp. 421-433, 1970.

[4] M. J. Frisch et al., "Gaussian 09, Revision B.01," ed. Wallingford CT: Gaussian, Inc., 2009.

[5] D. A. Daramola and G. G. Botte, "Theoretical study of ammonia oxidation on platinum clusters - Adsorption of ammonia and water fragments," Computational and Theoretical Chemistry, vol. 989, pp. 7 - 17, 2012.