Jossou Ericmoore, Malakkal Linu, Dzade Nelson Y, Claisse Antoine, Szpunar Barbara, Szpunar Jerzy
Department of Mechanical Engineering, College of Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon S7N 5A9, Saskatchewan, Canada.
School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, U.K.
J Phys Chem C Nanomater Interfaces. 2019 Aug 15;123(32):19453-19467. doi: 10.1021/acs.jpcc.9b03076. Epub 2019 Jul 11.
The interfacial interaction of USi with water leads to corrosion of nuclear fuels, which affects various processes in the nuclear fuel cycle. However, the mechanism and molecular-level insights into the early oxidation process of USi surfaces in the presence of water and oxygen are not fully understood. In this work, we present Hubbard-corrected density functional theory (DFT + ) calculations of the adsorption behavior of water on the low Miller indices of the pristine and defective surfaces as well as water dissociation and accompanied H formation mechanisms. The adsorption strength decreases in the order USi{001} > USi{110} > USi{111} for both molecular and dissociative HO adsorption. Consistent with the superior reactivity, dissociative water adsorption is most stable. We also explored the adsorption of HO on the oxygen-covered USi surface and showed that the preadsorbed oxygen could activate the OH bond and speed up the dissociation of HO. Generally, we found that during adsorption on the oxygen-covered, defective surface, multiple water molecules are thermodynamically more stable on the surface than the water monomer on the pristine surface. Mixed molecular and dissociative water adsorption modes are also noted to be stable on the {111} surface, whereas fully dissociative water adsorption is most stable on the {110} and {001} surfaces.
USi与水的界面相互作用会导致核燃料腐蚀，这会影响核燃料循环中的各种过程。然而，对于水和氧气存在下USi表面早期氧化过程的机理和分子层面的认识尚未完全明晰。在这项工作中，我们展示了哈伯德修正密度泛函理论（DFT + ）对水在原始和有缺陷表面的低米勒指数上的吸附行为以及水的解离和伴随的H形成机制的计算。对于分子态和离解态的HO吸附，吸附强度按USi{001} > USi{110} > USi{111}的顺序降低。与卓越的反应活性一致，离解态水吸附最稳定。我们还研究了HO在氧覆盖的USi表面上的吸附，结果表明预吸附的氧可以活化OH键并加速HO的解离。总体而言，我们发现在吸附到氧覆盖的有缺陷表面的过程中，多个水分子在表面上比原始表面上的水单体在热力学上更稳定。还注意到混合的分子态和离解态水吸附模式在{111}表面上是稳定的，而完全离解态水吸附在{110}和{001}表面上最稳定。
