Tokyo Tech News

Advanced X-Ray Technique Unveils Fast Solid-Gas Chemical Reaction Pathways


Published: May 2, 2023

Short-lived intermediate phases in solid-gas reactions can be captured with high-speed time-resolved synchrotron X-ray diffraction technique, demonstrate Tokyo Tech researchers. Their observation of the redox reaction pathway for layered perovskite, a high-performance oxygen storage material, enable them to access reaction data within a time window of few hundred milliseconds, highlighting the potential of the technique for optimizing solid-gas reactions.

Monitoring the Reaction Pathways of Fast Solid-Gas Reactions

For the rational design of new material compounds, it is important to understand the mechanisms underlying their synthesis. Analytical techniques such as nuclear magnetic resonance and spectroscopy are usually employed to study such mechanisms in molecular reactions. However, reaction pathways governing the formation of solid-state crystalline compounds remain poorly understood. This is partly due to the extreme temperatures and inhomogeneous reactions observed in solid-state compounds. Further, the presence of numerous atoms in solid crystalline compounds hinders precise analysis. Developing new techniques that can circumvent these challenges is, therefore, necessary.

More recently, in-situ synchrotron X-ray diffraction (XRD) techniques have been used for investigating reactions occurring in crystalline phases. Owing to their high speed and temporal resolution, synchrotron XRD measurements provide access to reaction data within extremely short time windows (few hundred milliseconds). This makes the technique promising for capturing data pertaining to short-lived intermediate reaction phases.

Now, a group of researchers from Japan have used such a state-of-the-art synchrotron XRD technique to report the topochemical solid-gas reduction mechanisms in layered perovskite. The study was led by Associate Professor Takafumi Yamamoto from Tokyo Institute of Technology (Tokyo Tech) and published in the journal Advanced Science.

"We used Sr3Fe2O7-δ, a Ruddlesden-Popper type layered perovskite, owing to its efficient oxygen storage ability. Sr3Fe2O7-δ undergoes reversible and fast topochemical redox reactions under O2 and H2 and shows excellent performance as an environmental catalyst material," explains Dr. Yamamoto.

His collaborators had previously observed that doping Sr3Fe2O7-δ with Palladium (Pd) significantly increases the oxygen release rate while decreasing the release temperature. Based on these observations, the team investigated the reaction pathways and structural evolution of this perovskite during the solid-gas reduction.

The team began by preparing a pristine sample and a Pd-loaded sample of Sr3Fe2O7-δ. They then used high-speed synchrotron XRD to monitor them as they underwent fast oxygen deintercalation (reduction).

The analyses revealed that the reduction of pristine Sr3Fe2O7-δ proceeded via thermodynamically stable phases, with pristine Sr3Fe2O7-δ undergoing gradual single-phase structural evolution during its reduction. In contrast, the reduction of Pd-loaded Sr3Fe2O7-δ involved nonequilibrium intermediate phases, a drastically different pathway. It first transformed into a dynamically-disordered phase for a few seconds and then rearranged itself via a first-order transition to reach the final ordered and stable state.

Additionally, Pd metal particles on the Sr3Fe2O7-δ surface significantly accelerated the oxygen deintercalation reaction of Pd-loaded Sr3Fe2O7-δ relative to that of pristine Sr3Fe2O7-δ. Dr. Yamamoto adds, "The change in reaction dynamics following the loading of Sr3Fe2O7-δ with Pd demonstrates that surface treatment can be used to manipulate reaction processes in a crystalline material."

In summary, these findings suggest that the synchrotron XRD technique can be leveraged to study reaction pathways in solid-state compounds as well as identify their rate-determining steps. This, in turn, could help optimize the reaction pathway for the rational design of high-performance functional materials.


Authors :
Takafumi Yamamoto1*, Shogo Kawaguchi2, Taiki Kosuge1, Akira Sugai1, Naoki Tsunoda1, Yu Kumagai1,3, Kosuke Beppu4, Takuya Ohmi1, Teppei Nagase1, Kotaro Higashi2, Kazuo Kato2, Kiyofumi Nitta2, Tomoya Uruga2, Seiji Yamazoe5,6, Fumiyasu Oba1, Tsunehiro Tanaka6,7, Masaki Azuma1,8,9, Saburo Hosokawa6,10*
Title :
Emergence of dynamically-disordered phases during fast oxygen deintercalation reaction of layered perovskite
Journal :
Advanced Science
Affiliations :

1 Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology

2 Japan Synchrotron Radiation Research Institute (JASRI)

3 Institute for Materials Research, Tohoku University

4 Department of Applied Chemistry for Environment, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University

5 Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University

6 Elements Strategy Initiative for Catalysts & Batteries (ESICB), Kyoto University

7 Department of Molecular Engineering, Graduate school of Engineering, Kyoto University

8 Living Systems Materialogy (LiSM) Research Group, International Research Frontiers Initiative (IRFI), Tokyo Institute of Technology

9 Kanagawa Institute of Industrial Science and Technology (KISTEC)

10 Faculty of Materials Science and Engineering, Kyoto Institute of Technology

* Corresponding authors' emails: (Takafumi Yamamoto); (Saburo Hosokawa)

Further Information

Associate Professor Takafumi Yamamoto

Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology



Public Relations Division, Tokyo Institute of Technology

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