The adsorption of several molecular and dissociative dihydrogen systems on a Pd-decorated graphene monolayer was studied using the density-functional theory. Our calculations show that the most favorable graphene-supported coordination structure is similar to the PdH 2 complex in vacuum, where the H-H bond is relaxed but not dissociated. We also computed overlap populations corresponding to bonds and atomic orbital interactions in order to study the evolution of the chemical bonding. During the decoration process with Pd, we detected a weakening of C-C bonds close to the adsorption site and the formation of strong C-Pd bonds, coming from interaction between C 2p z and Pd 5s, 5p z , and 4d z 2 orbitals. After H 2 molecule adsorption, the H-Pd bond is formed by the H 1s orbital overlap with the Pd 5s orbital, but this interaction became stronger during the atomic hydrogen adsorption. The objective of this work is to contribute to the understanding of the hydrogen uptake of Pd-doped graphene surfaces.

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