CuPt and CuPtRu nanostructures for Ammonia oxidation reaction
by Manso, Ryan H.; Song, L.; Liang, Z.; Wang, Jia X.; Chen, Jingyi
Liquid fuels, such as methanol, ethanol, and ammonia, are attractive alternative to hydrogen for fuel cells due to their lower costs for storage and distribution. Lack of sufficiently active catalysts for their oxidation reactions is a roadblock. Our previous study found that PtjCu nanodendrites yielded higher activity and durability than Pt nanoparticles for methanol oxidation reaction (MOR) in acid. In this study, we synthesized two types of nanostructures of CuPt and CuPtRu catalysts via seed-mediated growth of Pt and Ru on Cu and tested their performance for ammonia oxidation reaction (AOR) in alkaline solution. Unlike for MOR, the nanodendrites do not promote AOR activity - CuPt performs similar to Pt and CuPtRu is less active than Pt. Interestingly, the AOR peak current is increased by 64% on CuPt nanowires and 330% on CuPtRu nanowires as compared to Pt nanoparticles. These results suggest that AOR prefers extended surface on long nanowires, distinctly differing from MOR. This can be contributed to two factors: NH3 oxidization to N2 involves dimerization of two N-containing intermediates to form the N-N bond and diffusion batters for adsorbed intermediates are generally lower on terrace than at low-coordination sites. This demonstrated strong effect of surface morphology will be further studied and utilized in developing advanced AOR nanocatalysts. The Electrochemical Society.
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