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Controlling a spillover pathway with the molecular cork effect


Spillover of reactants from one active site to another is important in heterogeneous catalysis and has recently been shown to enhance hydrogen storage in a variety of materials1,2,3,4,5,6,7. The spillover of hydrogen is notoriously hard to detect or control1,2,4,5,6. We report herein that the hydrogen spillover pathway on a Pd/Cu alloy can be controlled by reversible adsorption of a spectator molecule. Pd atoms in the Cu surface serve as hydrogen dissociation sites from which H atoms can spillover onto surrounding Cu regions. Selective adsorption of CO at these atomic Pd sites is shown to either prevent the uptake of hydrogen on, or inhibit its desorption from, the surface. In this way, the hydrogen coverage on the whole surface can be controlled by molecular adsorption at a minority site, which we term a ‘molecular cork’ effect. We show that the molecular cork effect is present during a surface catalysed hydrogenation reaction and illustrate how it can be used as a method for controlling uptake and release of hydrogen in a model storage system1,2,4,5,6,8.

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Figure 1: Preferred binding sites for hydrogen and CO.
Figure 2: The molecular cork effect.
Figure 3: KMC simulations of the molecular cork effect.
Figure 4: The molecular cork effect in a hydrogenation reaction.


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We thank the Division of Chemical Sciences, Office of Basic Energy Sciences, Condensed Phase and Interfacial Molecular Science Program, US Department of Energy under Grant No. FG02-10ER16170. (M.D.M, G.K., E.A.L. and E.C.H.S.) and NSF (CHE-0844343) for partial support (M.B.B. and C.J.M.). E.A.L. acknowledges the Department of Education for a GAANN fellowship. A.D.J. acknowledges the National Science Foundation for a graduate fellowship. M.S. acknowledges the use of the UCL Legion High Performance Computing Facility (Legion@UCL) and associated support services, as well as support from the Thomas Young Centre: the London Centre for Theory and Simulation of Materials, for the completion of the theoretical part of this work.

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M.D.M., A.D.J., M.B.B., E.A.L., C.J.M. and G.K. performed the experiments. M.D.M., A.D.J., G.K. and E.C.H.S. performed the data analysis. M.S. performed the KMC simulations and post-processing. The paper was written by M.D.M., G.K., M.S. and E.C.H.S.

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Correspondence to E. Charles H. Sykes.

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Marcinkowski, M., Jewell, A., Stamatakis, M. et al. Controlling a spillover pathway with the molecular cork effect. Nature Mater 12, 523–528 (2013).

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