Hydrogen spillover on MoO3 (010) surface in the presence of a platinum and palladium catalyst was modeled using periodic density functional theory (DFT). The migration of H from a saturated Pt6 cluster to MoO3 (010) surface was found to undergo a transition from repulsive electrostatic to attractive proton-oxygen interactions. The hydrogen is able to move nearly freely in the interface and diffuse into the bulk lattice at ambient temperatures. We show that the high mobility is largely attributed to the massive H-bonding network in the MoO3 lattice.