Dissociation Mechanism of Water Molecules on the PuO₂(110) Surface: An Ab Initio Molecular Dynamics Study

Abstract

Reactions between water and plutonium oxide play a key role in determining the oxidation and corrosion rates of plutonium materials. We perform consecutive ab initio molecular dynamics simulations with the DFT + U approach, systematically studying the dissociation dynamics and mechanism of water molecule and small clusters on the PuO 2 (110) surface. The dissociation of water on the surface is found to be a two-step hydroxylation process for both monomer and clusters, but different dissociation mechanisms are revealed. Water monomer dissociation, as the consequence of the hybridizations between the molecular orbitals of water and the electronic state of the surface, needs to overcome a reaction energy barrier of 0.18 eV. In contrast, the dissociations of hydrogen-bonded small water clusters are exothermic by −0.42 eV with no transition energy barrier. Hydrogen-bonding interactions between water molecules facilitate the dissociation process and result in a more stable dissociation state with respect to that of a single molecule. Such interaction also induces a hydrogen-transfer reaction between formed surface hydroxyl group and the remaining water molecule.

Effects of Hydration on the Adsorption of Benzohydroxamic Acid on the Lead-Ion-Activated Cassiterite Surface: A DFT Study

“…Interfacial phenomena, such as photocatalytic water splitting, heterogeneous catalysis, electrochemistry, and surface adsorption, show that water can react with the active sites on the solid surface . Surface active sites can be hydrated by hydroxyls or water molecules. − The presence of hydration layer on the surface treated/untreated by metal ions usually has a strong influence on the adsorption of collectors. , The adsorption of flotation reagents on the metal-ion-activated surface is usually stronger than that on the hydrated surface. , However, in flotation systems, hydration and dehydration of water/oxide–mineral interfaces, especially in the presence of activated ions, remain poorly understood.…”

Water on Actinide Dioxide Surfaces: A Review of Recent Progress

“…It was found that the dissociative adsorption of H2O is feasible for a large range of temperature and water partial pressures on UO2 (111) surface [69]. The dissociation of H2O on PuO2 (110) surface is a two-step hydroxylation process both for single H2O molecule and H2O clusters [70]. The dissociation is initiated by the [70].…”

“…The dissociation of H2O on PuO2 (110) surface is a two-step hydroxylation process both for single H2O molecule and H2O clusters [70]. The dissociation is initiated by the [70]. The dissociation is initiated by the dehydrogenation of water molecules to form a hydroxyl group with surface oxygen atom, followed by successive surface hydroxylation on plutonium with the remaining hydroxide ion of the dissociating molecule.…”

“…The H 2 O molecule dissociates as the consequence of hybridizations between the molecular orbitals of water and the electronic state of the surface with a reaction energy barrier of 0.18 eV. In contrast, the dissociation of H 2 O clusters is exothermic by −0.42 eV with no energy barrier [70].…”

First-Principles Study of Nitrogen Adsorption and Dissociation on PuH2 (111) Surface

“…Plutonium is one of the main materials used in nuclear applications, and considerable experimental and theoretical efforts have been devoted to studying the structures and properties of elementary plutonium as well as its compounds [1][2][3][4][5]. For the safety of long-term storage of plutonium, a series of reactions may be involved, such as Pu [6][7][8][9][10].…”