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Hydrogen atoms at the palladium surface, at the MgO surface and at the Pd-MgO metal-support boundary. Towards computer modelling of the spillover effect

Bartczak W.M., Stawowska J.

Materials Science Poland

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2006

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Vol. 24, No. 2/1

421--432

EN

The work is devoted to computer modelling of interactions of atomic hydrogen with palladium and MgO surfaces, and with Pd atoms adsorbed on MgO surface. Quantum calculations were performed using the methods of the Density Functional Theory (DFT) with gradient-corrected functionals for electron exchange and correlation. The potential energy surfaces were calculated for a hydrogen atom interacting with Pd and MgO surfaces. The results indicate an easy (0.17 eV activation barrier) diffusion of hydrogen atoms over the metal surface. A possibility of migration of H atoms from the metal surface onto the MgO support surface (the "spillover effect") is discussed. It was found that the transfer of a hydrogen atom from the vicinity of a Pd atom to O sites of the MgO surface results in the energy gain of the order of 0.5 eV. The transfer, however, is an activated process with the activation energy about 0.8 eV.

2

Hydrogen Atom and Hydrogen Ion Interactions with the [100] Surface of Transition Metals (Pd, Ni, Ag, Cu)

Bartczak W., Romanowski S., Stawowska J.

Polish Journal of Chemistry

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2004

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Vol. 78 / nr 9

1103-1119

EN

Quantum calculations of interaction of the atomic hydrogen with metal (Pd, Ni, Ag, Cu) clusters with the structure of the fcc [100] surface have been performed. The calculations have been based on the gradient-corrected methods of the Density Functional Theory. For a given position (X,Y) of the hydrogen atom over the metal plane the distance Z from the plane was optimized in order to obtain the highest binding energy which was defined as the difference between the total energy of the H-Me cluster and the energy of the separate H atom and metal cluster. The results of the calculations allowed us to construct the Potential Energy Surfaces for a series of systems. It appears that the H atom binding energy along the valley perpendicular to the metal-metal bond varies only slightly. This suggests easy diffusion of hydrogen along this path. The potential barrier for the hydrogen diffusion over palladium surface is of the order of 0.17 eV. In the case of Ni, Ag and Cu we observe potential barriers with a maximum above the metal-metal bond, with the barrier height 0.68 eV, 0.62 eV and 0.79 eV, respectively. Separate calculations have been performed for the positively charged clusters. For the case of the charged clusters the potential barriers are lower than the value for the neutral clusters. The barriers are 0.27 eV for Ni, 0.35 eV for Ag and 0.58 eV for Cu. For Pd the barrier for the positively charged cluster is 0.5 eV, higher than the value for the neutral case, but for the negatively charged cluster the barrier is practically 0.The results of calculations for all the cases considered suggest the possibility of easy, sometimes activationless, diffusion of hydrogen atoms over the metal surface.

3

Proces reformingu metalu ditlenkiem węgla : możliwości badawcze metod symulacji komputerowej

Bartczak W. M., Stawowska J.

Przemysł Chemiczny

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2003

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T. 82, nr 3

193-198

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Oddziaływanie wodoru z powierzchnią katalizatorów bimetalicznych

Bartczak W. M., Stawowska J., Romanowski S.

Przemysł Chemiczny

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2003

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T. 82, nr 8-9

664-670

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Modelowanie komputerowe procesu dezaktywacji katalizatora metalicznego przez depozyt węglowy

Stawowska J., Bartczak W. M.

Przemysł Chemiczny

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2003

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T. 82, nr 8-9

778-782