Adsorption, dissociation and diffusion behavior of H2O on the PuO2(111) surface from DFT + U-D3: the role of hydrogen bonding

Abstract

The interaction between H₂O and plutonium oxide is an essential aspect of researching plutonium corrosion. We systematically studied the adsorption, dissociation, and diffusion of H₂O molecules on the PuO₂(111) surface with the DFT + U-D3 scheme. We find that the top of the Pu atom is the most stable adsorption site for H₂O molecules on the PuO₂(111) surface. When multiple H₂O molecules are adsorbed, hydrogen bonding between molecules can increase the average adsorption energy. H₂O molecules will dissociate into H atoms and O–H groups under certain conditions. We have paid special attention to the role of hydrogen bonds between H₂O molecules. When the coverage of H₂O molecules is low, hydrogen bonds can significantly promote the adsorption and dissociation of H₂O molecules. And H₂O tends to exist on the surface of plutonium oxide in dissociated and molecular mixed states. The H atoms produced by the dissociation of H₂O molecules are not easily diffused, which may be related to the hydrogen bonding between O–H groups. This work has important theoretical significance for deepening the understanding of the corrosion mechanism of plutonium.