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Issue 32, 2010
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First principles study of doped carbon supports for enhanced platinum catalysts

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Abstract

Highly oriented pyrolytic graphite (HOPG) implanted with N, Ar and B is studied as a support for platinum nanoparticle catalysts for fuel cells. Experimentally, we find that Pt supported by N-HOPG is more disperse, more catalytically active and suffers less particle ripening than native HOPG, while Pt supported on Ar-irradiated HOPG is slightly more active but ripens more than Pt on native HOPG. Defective HOPG supports are modeled by density functional theory (DFT) calculations that confirm and explain the above experimental results. First, defect energetics are studied to demonstrate that nitrogen doping at high doses likely causes agglomerated nitrogenous defect clusters, and irradiation with Ar ions creates vacancies that agglomerate in vacancy clusters. Second, Pt catalyst particle nucleation and agglomeration is studied. For Pt clusters supported on HOPG with nitrogen defects, calculations show a greater driving force for nucleation and greater particle tethering. For Pt clusters supported on HOPG with vacancy aggregations, this study shows a strong driving force for nucleation and a much enhanced tendency for particle ripening. Third, the electronic structure of Pt clusters on different supports is calculated. Finally, reaction energetics are calculated for two likely reaction pathways over Pt clusters supported on different HOPG substrates. PtN-HOPG shows modified electronic structure of the Pt catalyst and increased activity towards oxygen. PtAr-HOPG shows slightly enhanced catalytic activity towards oxygen. In all respects, the findings agree with experiment. The calculations attribute the catalytic activity changes primarily to changes in the workfunction and secondarily to the d-band structure of supported Pt particles.

Graphical abstract: First principles study of doped carbon supports for enhanced platinum catalysts

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Publication details

The article was received on 24 Dec 2009, accepted on 22 Apr 2010 and first published on 23 Jun 2010


Article type: Paper
DOI: 10.1039/B927263A
Citation: Phys. Chem. Chem. Phys., 2010,12, 9461-9468
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    First principles study of doped carbon supports for enhanced platinum catalysts

    T. Holme, Y. Zhou, R. Pasquarelli and R. O'Hayre, Phys. Chem. Chem. Phys., 2010, 12, 9461
    DOI: 10.1039/B927263A

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