Catalytic Performance Comparison of Shape-Dependent Nanocrystals and Oriented Ultrathin Films of Pt4Cu Alloy in the Formic Acid Oxidation Process
Research efforts continue to focus on the development of viable and cost-effective fuel cell catalysts with minimized Pt content. This work presents a comparative study between Pt4Cu nanocubes and nano-octahedra as well as Pt4Cu (100) and (111) thin films used as catalysts for formic acid oxidation. This paper introduces a novel synthetic method for Pt4Cu nano-octahedra, and it also demonstrates for the first time the use of surface limited redox replacement of Pb underpotentially deposited layer for epitaxial growth of thin alloy films. Overall, the nanoparticle catalysts exhibit superior performance in terms of durability when compared to their thin film counterparts but feature nearly fivefold lower activity. As a result, it was determined that both types of catalysts accumulate nearly equal charge density in their lifespan. In terms of crystallographic orientation, the results indicate that the nanocubes and Pt4Cu (100) thin films outperform the nano-octahedra and Pt4Cu (111) thin films in terms of durability but feature equal to slightly lower activity. This significant difference in durability of catalysts with different crystallographic orientation is attributed to interplay of passivation (from CO poisoning and Pt oxidation) and dissolution of Pt. When compared to pure Pt catalysts (nanoparticles and thin films), all of the Pt4Cu catalysts in this work exhibit superior performance toward formic acid oxidation in terms of activity and durability.
KeywordsPtCu alloy Formic acid oxidation Fuel cells Catalyst Activity Durability
L.B., M.F., and N.D. acknowledge the financial support of the National Science Foundation, Division of Materials Research (DMR-0742016). L.B. acknowledges the financial support of the Clifford D. Clark Fellowship, Y.W and J.F. acknowledge the financial support of General Motor LLC., and B.M., J.Z., D.X., and J.F. acknowledge the financial support of NSF DMR-0731382.
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