Excess Electrons on Reduced AnO2 (111) Surfaces (An = Th, U, Pu) and Their Impacts on Catalytic Water Splitting

• Published in: Journal of physical chemistry. C Vol. 123; no. 50; pp. 30245 - 30251
• Main Authors: Wang, Gaoxue, Batista, Enrique R, Yang, Ping
• Format: Journal Article
• Language: English
• Published: American Chemical Society 19.12.2019
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.9b06543

Excess electrons from intrinsic oxygen vacancies play a key role in the surface chemistry and catalytic properties of metal oxides. This effect is particularly critical in actinide dioxides (AnO2), the most common nuclear fuels, where radiation can induce the formation of vacancies. However, the behavior of excess electrons on AnO2 surfaces has not been fully explored. In this article, we present a first-principle study of the electronic structure of excess electrons from oxygen vacancies on AnO2 (111) surfaces (An = Th, U, Pu). The low-energy solutions for the excess electrons are searched via U-ramping and occupation matrix control. The excess electrons are found to localize at the vacancy site on ThO2 and move to the metal 5f orbitals on the PuO2 surface, with UO2 as the intermediate case. This change significantly affects the catalytic properties of the AnO2 surfaces. In the presence of water, the excess electrons lead to the exothermic splitting of H2O and formation of molecular H2 on ThO2 and UO2 surfaces, while on the PuO2 surface the formation of H2 is thermodynamically unfavorable. This work has vital implications in the surface chemistry and corrosion of AnO2 and hence the handling and long-term storage of spent nuclear fuels.