Catalytic property of Pt catalysts can be altered significantly by the nature of facets exposed. Pt (100) plane excels in activity/selectivity compared to other planes in many reactions, including ring-opening hydrogenation of pyrroles, benzene hydrogenation, methanol oxidation, and electro-oxidation of ammonia. The findings have stimulated the exploration of new methods for preparing cubic Pt catalysts. Various wet chemical approaches have been reported recently for making Pt nanocubes. However, the employed organic agents lead to severe contamination problems and require complete removal from the Pt surface before it becomes catalytically active. Moreover, the complexity of preparative procedures and the difficulties in scaling them up have limited the wet chemistry to fundamental studies and made them less useful for real applications. On the other hand, conventional impregnation method is broadly used in industry and catalysis research for its simple procedure and scaling-up capability. However, the method has little control over uniformity of particle size and composition, not to mention shape of Pt.The present work develops a facile, surfactant-free, and scalable method for production of cubic Pt/C. The method hybridizes the impregnation and wet chemistry methods to combine the advantages of both techniques. By impregnating Pt precursors on a carbon support and employing CO as a functional gas during the reduction process, uniform Pt nanoparticles can be produced and well dispersed. By avoiding the use of any organic agents, the CO gas-assisted synthesis is a facile one-step approach and can be readily scalable. Electrochemical oxidation of ammonia, due to its important applications in fuel cells and environmental catalysis, is studied as a model reaction to investigate shape effect of Pt catalysts. It is shown that the cubic Pt/C exhibits significantly higher activity than Pt/C in other shapes.

Engineering large-scale production of cubic platinum/carbon catalysts and the shape effect in electrocatalytic oxidation of ammonia

246th National Meeting (2013)

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