## Abstract

The interaction of Pd_{N} clusters (N = 2, 3, 4, 7, and 13) with multiple H_{2} adsorbate molecules is investigated using density functional theory with the hybrid PBE0 functional. The optimal structure for each Pd_{N}H_{2(L)} complex is determined systematically via a sequential addition of H_{2} units. The adsorption energy for each successive H_{2} addition is computed to determine the maximum number of molecules that can be stably added to a Pd_{N} at T = 0 K. The Gibbs free energy is then used to determine the saturation coverage at finite temperature. For N = 2, 3, and 4, a single H_{2} is found to dissociate, and up to two additional molecular H_{2} units per Pd atom can bind stably to the clusters at 0 K. At 300 K, one H_{2} unit dissociates, and only one additional H_{2} molecular unit per Pd atom is stably bound. For N = 7 and T = 0 K, two H_{2} units dissociate, and 11 additional H_{2} units bind molecularly. At 300 K, two units dissociate, and eight are bound molecularly. For N = 3, 4, and 7, we find that an additional H_{2} unit may dissociate if the underlying cluster structure rearranges. Eight H_{2} units dissociate on Pd_{13} at 0 K. At least one additional H_{2} binds molecularly at 0 K, but none bind at 300 K. This suggests that only dissociated H_{2} units will stably bind to larger Pd particles at room temperature. The influence of molecularly adsorbed H_{2} units on the migration of dissociated H atoms is investigated in a preliminary way. Both barrier heights and the relative stability of local minima of Pd_{4}H_{2(L)} are found to be affected by the degree of molecular H_{2} coverage.

Original language | English |
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Pages (from-to) | 3594-3603 |

Number of pages | 10 |

Journal | Journal of Physical Chemistry A |

Volume | 119 |

Issue number | 15 |

DOIs | |

State | Published - Apr 16 2015 |

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