In Situ Small-Angle Neutron Scattering Analysis of the Initial Deuteride Formation of Deuterium–Cerium Reactions under a Controlled Gas Flow

Abstract

Metrics & MoreArticle RecommendationsABSTRACT: "Real-life" metals inevitably form the oxide layer, thus leading to complex initial hydriding processes, which are still unclear because of the experimental challenges in monitoring elemental steps including surface sorption, permeation, and concentration of hydrogen. In this study, the deuteride precipitation caused by the concentration of deuterium was successfully measured by the in situ small-angle neutron scattering (SANS) method, which used a selfdesigned reaction chamber to give rise to the scattering signals of the surface structure. In addition, in the measurements of activated cerium samples, surface sorption of deuterium could be modified to form a constant flow in order to further explore the initial hydriding processes. The formation of deuterides was found to occur as soon as deuterium was absorbed in the samples with a thin oxide layer and the subsequent growth of deuterides depended on the amount of consumed D 2 . However, the sample with a thick oxide layer showed the delayed precipitation of deuterides and the decelerated subsequent growth of deuterides without inhibiting the surface absorption of deuterium. The in situ SANS method showed the high sensitivity to the deuteride phase on the surface at a deuterium amount of 0.2 μmol cm −2 D 2 for cerium and a great potential in exploring the mechanism of early incipient stages of hydrogen reactions.

Neutron Scattering Studies of Heterogeneous Catalysis

“…(a) A schematic diagram of the in situ SANS experiment of the deuterium-cerium reaction. Reproduced with permission from ref . Copyright 2020 American Chemical Society.…”

“…With the development of in situ setups, in situ SANS has been used to investigate several different systems, as demonstrated in Figure . By using in situ SANS and a custom reaction chamber (Figure a), Yan et al studied deuteride formation on the surface of cerium (coated with a surface oxide layer). , It was found that deuterides were formed as soon as deuterium was absorbed on the sample with a thin oxide layer, while for the sample with a thick oxide layer, the precipitation of deuterides was delayed . Prabhu et al developed an in situ electrochemical SANS methodology, which enabled direct measurements of nanomaterial dispersion structure under redox reactions at the vitreous carbon electrode (Figure b). , A feasibility test was performed on ZnO nanoparticles in 50 mmol/L NaCl deuterium oxide solution under bulk electrolysis at negative potentials. , The in situ SANS results showed irreversible nanoparticle structural changes during the potential cycle. , To follow the structural changes under continuous chemical reactions, Hayward et al proposed to use the setup shown in Figure c for SANS experiments .…”

“…By using in situ SANS and a custom reaction chamber (Figure 60a), Yan et al studied deuteride formation on the surface of cerium (coated with a surface oxide layer). 436,437 It was found that deuterides were formed as soon as deuterium was absorbed on the sample with a thin oxide layer, while for the sample with a thick oxide layer, the precipitation of deuterides was delayed. 436 Prabhu et al developed an in situ electrochemical SANS methodology, which enabled direct measurements of nanomaterial dispersion structure under redox reactions at the vitreous carbon electrode (Figure 60b).…”

“…436,437 It was found that deuterides were formed as soon as deuterium was absorbed on the sample with a thin oxide layer, while for the sample with a thick oxide layer, the precipitation of deuterides was delayed. 436 Prabhu et al developed an in situ electrochemical SANS methodology, which enabled direct measurements of nanomaterial dispersion structure under redox reactions at the vitreous carbon electrode (Figure 60b). 438,439 A feasibility test was performed on ZnO nanoparticles in 50 mmol/L NaCl deuterium oxide solution under bulk electrolysis at negative potentials.…”