Watching an oxide reinvent itself in real time: in situ neutron diffraction reveals how activation history steers Ruddlesden–Popper oxides toward fuel-cell or catalyst behaviour

Mona Bahout ^a and Thomas C. Hansen ^b

^aUniversité de Rennes, CNRS, ISCR – UMR 6226, F-35000 Rennes, France
^bInstitut Laue-Langevin, 38042 Grenoble Cedex 9, France

M. Bahout, T. T. D. Nguyen, E. Quenard, T. C. Hansen, V. Dorcet, M. Araque, S. Paofai, N. Dumait, A. Le Gal La Salle, O. Joubert, Activation-engineered Sr-rich Ruddlesden–Popper oxides for robust SOFC and dry reforming catalysis, Next Energy (2026).

Raw neutron diffraction data (ILL, D20): DOI10.5291/ILL-DATA.5-25-289.

Supplementary data (Zenodo): DOI 10.5281/zenodo.17160548.

https://doi.org/10.1016/j.nxener.2026.100680

Materials for clean energy are almost always designed to be stable. This study turns that logic on its head: by deliberately controlling how an oxide is reduced — its “activation history” — a single starting material can be steered toward two completely different jobs, without changing its chemical composition. The authors call this activation engineering. Starting from a strontium-rich layered oxide, Ln₀.₅Sr₁.₅Mn₀.₇Ni₀.₃O₄ (Ln = La or Pr), a mild reduction exsolves about 1 wt% of metallic nickel and yields an excellent fuel-cell anode (an area-specific resistance of 0.74 Ω·cm² at 700 °C, the best value yet reported for this family of oxides). A more intense reduction exsolves roughly 5 wt% Ni and instead produces a robust catalyst for the dry reforming of methane, converting the greenhouse gases CH₄ and CO₂ into useful syngas for more than 28 hours.

The role of neutrons. The heart of the demonstration is real-time, in situ neutron powder diffraction performed on the high-intensity D20 diffractometer at the Institut Laue-Langevin (ILL, Grenoble), where a full diffraction pattern was recorded every two minutes while the sample was heated under a reducing gas and then exposed to a CH₄/CO₂ mixture. Neutrons are uniquely suited to this problem: unlike X-rays, they “see” oxygen atoms clearly even when heavy elements such as lanthanum, praseodymium and strontium are present. This let the team follow the exact sequence of transformations as they happened — first the segregation of SrO near 800 °C, then, about 100 °C higher, the appearance of metallic nickel particles, and finally the hydration of SrO into Sr(OH)₂ on cooling. For the praseodymium compound, the neutrons captured a structural collapse under CO₂ in real time: the framework rapidly converted into strontium carbonate (up to ~40 wt% within five hours), destroying the useful layered structure, as shown in Figure 1. Quantified step by step through Rietveld refinement, these neutron measurements establish that it is the activation history — not the composition — that decides the fate of the material. This time-resolved, oxygen-sensitive view is something only neutrons could provide, and it is what makes “activation engineering” a predictable design tool rather than a lucky accident.