Density functional calculation of adsorption and dissociation of PbPo molecule on Pd(100), Pd(110) and Pd(111) surfaces

Radiotoxic Po are produced and mainly formed as PbPo in lead-bismuth eutectic in lead-bismuth fast reactor and accelerator-drive systems during normal operation. Part of hazardous PbPo will evaporate and accumulate in the cover gas above the lead bismuth eutectic coolant. To ensure safe handling of the reactor, suitable cover gas filter systems should be fixed but few fundamental data on the interaction between PbPo and filter materials are reported. In this work, adsorption and dissociation of PbPo molecule on candidate filter material Pd surfaces were studied with the density functional theory. It was found PbPo is strongly chemisorbed on Pd(100), Pd(110) and Pd(111) surfaces with adsorption energies in the range of-1.14 eV to-5.36 eV. The activation energies for PbPo dissociation on these tree surfaces are all very small, which are one to two order of magnitude smaller than the recombination activation energies of the reversed paths. The calculated results indicate that strong chemi-sorption was found between PbPo and perfect low-index Pd surfaces and PbPo molecule is highly inclined to be as Pb and Po atoms on these surfaces.