Adsorption Properties Of H₂O On Be, Zr And CeO₂Surfaces: First-principles Calculations

Using frst-principles calculations within density functional theory, we systemati-cally studied the adsorption behavior of H₂O on material surfaces, including Be（0001）,Zr（0001） and CeO₂（111）.We frstly investigated the adsorption properties of single H₂O molecule and clus-ters on Be（0001） surface. We found that the favored molecular adsorption site is the topsite with an adsorption energy of about-0.30eV, together with the detailed electronicstructure analysis, suggesting a weak binding strength of the H₂O/Be（0001） surface.The adsorption interaction is mainly contributed by the overlapping between the s andpzstates of the top-layer Be atom and the molecular orbitals1b1and3a1of H₂O. Theactivation energy for H₂O difusion on the surface is about0.30eV. Meanwhile, ourstudy indicates that no dissociation state exists for the H₂O/Be（0001） surface. For theH₂O clusters adsorption, several cluster structures at diferent coverages were iden-tifed, including dimer, trimer, tetramer, hexamer, between which the2×2hexamerbilayer structure at coverage of0.5monolayer is the most energetic favorable.Secondly, the adsorption and dissociation of isolated H₂O molecule on Zr（0001）surface were theoretically studied in detail. It was shown that the flat adsorption stateson the top site are dominated by the1b1-d band coupling, insensitive to the azimuthalorientation. The difusion between adjacent top sites reveals that the water molecule isvery mobile on the surface. For the upright adsorption confguration on the bridge site,the surfaceâ†'water charge transfer occurring across the Fermi level plays an importantrole. The dissociation of H₂O on Zr（0001） surface is very facile, in good accordancewith the attainable experimental results.Finally, we studied the adsorption properties of isolated H₂O molecule on stoi-chiometric and reduced CeO₂（111） surfaces by frst-principles calculations and molec-ular dynamics simulations. We found that the most stable adsorption confgurationsform two hydrogen bonds between the adsorbate and substrate. The water molecule is very inert on the stoichiometric surface unless up to a high temperature of600K.For the reduced surface, we found that the oxygen vacancy enhances the interaction.Moreover, simulations at low temperature100K confrm that it is facilitated for waterto dissociate into H and OH species.