Activation engineered Sr rich Ruddlesden–Popper oxides for robust SOFC and dry reforming catalysis

Activation engineering is proposed as a process-centric design strategy that shifts focus from stabilizing pristine oxides to tailoring metastable states through controlled reduction histories to unlock functional properties inaccessible at thermodynamic equilibrium. Unlike defect engineering or conventional doping, it operates exclusively through process variables applied to a fixed precursor to address United Nations SDGs 7, 9, and 13. Using real-time in situ neutron diffraction on layered Ruddlesden–Popper (RP, A n+1 B n O 3n+1 ) oxides, Ln₀.₅Sr₁.₅Mn₀.₇Ni₀.₃O₄ (LN3 for Ln = La; PN3 for Ln = Pr), we demonstrate that a single precursor can be steered toward divergent functional architectures. A moderate activation (5% H₂/N₂, 700°C, 48 h) exsolves ≈1 wt% Ni, templated by surface SrO nanodomains, creating a Solid Oxide Fuel Cell anode with a benchmark Area Specific Resistance, ASR of 0.74 Ω·cm² for RP oxides at 700 °C, stable over 135 hours. Conversely, intense activation (pure H 2 , 750 °C, 12 h) drives deep reduction ≈5 wt% Ni exsolution), enabling >28 hours of dry reforming stability at 39% CH 4 conversion. Crucially, Raman spectroscopy and Transmission electron microscopy (TEM) reveal an exsolution paradox : PN3 exsolves finer particles, they undergo rapid graphitic encapsulation (I D /I G ≈ 1.3±0.2), whereas LN3 accumulates carbon in a dispersed, Raman-invisible morphology that leaves active sites accessible. Post-reaction analysis rationalizes these divergent fates through contrasting reconstruction pathways: LN3 transforms into a stable Ni/La 2 O 2 CO 3 /LaMnO 3 nanocomposite where the oxycarbonate buffer sustains activity, whereas PN3 undergoes structural collapse. These findings validate activation history as a primary design variable for crafting multifunctional energy materials.