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Ru–Pt core–shell nanoparticles for preferential oxidation of carbon monoxide in hydrogen

Abstract

Most of the world’s hydrogen supply is currently obtained by reforming hydrocarbons. ‘Reformate’ hydrogen contains significant quantities of CO that poison current hydrogen fuel-cell devices. Catalysts are needed to remove CO from hydrogen through selective oxidation. Here, we report first-principles-guided synthesis of a nanoparticle catalyst comprising a Ru core covered with an approximately 1–2-monolayer-thick shell of Pt atoms. The distinct catalytic properties of these well-characterized core–shell nanoparticles were demonstrated for preferential CO oxidation in hydrogen feeds and subsequent hydrogen light-off. For H2 streams containing 1,000 p.p.m. CO, H2 light-off is complete by 30 C, which is significantly better than for traditional PtRu nano-alloys (85 C), monometallic mixtures of nanoparticles (93 C) and pure Pt particles (170 C). Density functional theory studies suggest that the enhanced catalytic activity for the core–shell nanoparticle originates from a combination of an increased availability of CO-free Pt surface sites on the Ru@Pt nanoparticles and a hydrogen-mediated low-temperature CO oxidation process that is clearly distinct from the traditional bifunctional CO oxidation mechanism.

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Figure 1: Graphical representation of alloy, core–shell and linked monometallic nanoparticles in the Pt–Ru bimetallic system.
Figure 2: TEM images.
Figure 3: XRD profiles.
Figure 4: Fourier-transform infrared spectra.
Figure 5: Catalytic results for core–shell and alloy PtRu particles.
Figure 6: PROX reaction mechanisms.

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Acknowledgements

Work at Maryland was supported by the National Science Foundation under Grant No. 0401850, the University of Maryland Energy Research Center (UMERC). Work at UW-Madison was supported by DOE-BES, Chemical Sciences Division (DE-FG02-05ER15731 and DE-FG02-03ER15468), and S.C. Johnson. Supercomputing time at DOE-NERSC, PNNL and ORNL facilities is greatly appreciated. A.U.N. thanks L. Grabow for his valuable help.

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Correspondence to Manos Mavrikakis or Bryan Eichhorn.

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Supplementary Tables S1–S2, Supplementary Figures Fig. S1 and Fig. S2 (PDF 387 kb)

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Alayoglu, S., Nilekar, A., Mavrikakis, M. et al. Ru–Pt core–shell nanoparticles for preferential oxidation of carbon monoxide in hydrogen. Nature Mater 7, 333–338 (2008). https://doi.org/10.1038/nmat2156

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