During reaction, a catalyst surface usually interacts with a constantly fluctuating mix of reactants, products, ‘spectators’ that do not participate in the reaction, and species that either promote or inhibit the activity of the catalyst. How molecules adsorb and dissociate under such dynamic conditions is often poorly understood. For example, the dissociative adsorption of the diatomic molecule H2—a central step in many industrially important catalytic processes—is generally assumed1 to require at least two adjacent and empty atomic adsorption sites (or vacancies). The creation of active sites for H2 dissociation will thus involve the formation of individual vacancies and their subsequent diffusion and aggregation2,3,4,5,6, with the coupling between these events determining the activity of the catalyst surface. But even though active sites are the central component of most reaction models, the processes controlling their formation, and hence the activity of a catalyst surface, have never been captured experimentally. Here we report scanning tunnelling microscopy observations of the transient formation of active sites for the dissociative adsorption of H2 molecules on a palladium (111) surface. We find, contrary to conventional thinking1, that two-vacancy sites seem inactive, and that aggregates of three or more hydrogen vacancies are required for efficient H2 dissociation.
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Conrad, H., Ertl, G. & Latta, E. E. Adsorption of hydrogen on palladium single crystal surfaces. Surf. Sci. 41, 435–446 (1974)
Taylor, H. S. Theory of the catalytic surface. Proc. R. Soc. Lond. A 108, 105–111 (1925)
Boudart, M. Four decades of active centers. Am. Sci. 57, 97–111 (1969)
Ponec, V. & Sachtler, W. M. H. The reactions between cyclopentane and deuterium on nickel and nickel-copper alloys. J. Catal. 24, 250–261 (1972)
Sinfelt, J. H. Bimetallic Catalysts: Discoveries, Concepts and Applications (Wiley and Sons, New York, 1983)
Somorjai, G. A. Introduction to Surface Chemistry and Catalysis (Wiley and Sons, New York, 1994)
Behler, S. et al. A scanning tunneling microscope with continuous flow cryostat sample cooling. Rev. Sci. Instrum. 68, 2479–2485 (1997)
Felter, T. E., Sowa, E. C. & Van Hove, M. A. Location of hydrogen on palladium (111) studied by low-energy electron diffraction. Phys. Rev. B 40, 891–899 (1989)
Paul, J. F. & Sautet, P. Density-functional periodic study of the adsorption of hydrogen on a palladium (111) surface. Phys. Rev. B 53, 8015–8027 (1996)
Lovvik, O. M. & Olsen, R. A. Adsorption energies and ordered structures of hydrogen on Pd(111) from density functional periodic calculations. Phys. Rev. B 58, 10890–10898 (1998)
Mitsui, T., Rose, M. K., Fomin, E., Ogletree, D. F. & Salmeron, M. Hydrogen adsorption and diffusion on Pd(111). Surf. Sci. (submitted)
This work was supported by the Office of Basic Energy Science of the US Department of Energy.
The authors declare that they have no competing financial interests.
About this article
Cite this article
Mitsui, T., Rose, M., Fomin, E. et al. Dissociative hydrogen adsorption on palladium requires aggregates of three or more vacancies. Nature 422, 705–707 (2003). https://doi.org/10.1038/nature01557
Journal of Solid State Chemistry (2020)
Pd3Ag(111) as a Model System for Hydrogen Separation Membranes: Combined Effects of CO Adsorption and Surface Termination on the Activation of Molecular Hydrogen
Topics in Catalysis (2020)
Impact of Surfactants and Stabilizers on Palladium Nanoparticle–Hydrogen Interaction Kinetics: Implications for Hydrogen Sensors
ACS Applied Nano Materials (2020)
Physical Chemistry Chemical Physics (2020)
Catalysis Today (2020)