Redox-Driven Ni Exsolution with Embedded Ru-Rich Clusters from LaNi 0.95 Ru 0.05 O ₃

Exsolved nanoparticles from perovskite oxides provide a route to creating thermally stable, socketed nanostructures with tunable composition and morphology. Here, LaNiO 3 (LNO) and Ru-doped LaNiO 3 (LaNi 0.95 Ru 0.05 O 3, LN95R5) were synthesized via a modified sol–gel method to investigate how synthesis parameters and redox conditions govern bimetallic exsolution and nanoscale architecture. Calcination temperatures between 700 and 900 °C and reduction treatments spanning 600–800 °C with dwell times from 30 min to 2 h were systematically varied. Ex situ electron microscopy reveals that lower calcination temperatures combined with more aggressive reduction promote enhanced exsolution and higher nanoparticle dispersion. In situ X-ray absorption spectroscopy directly tracks the redox evolution of Ni and Ru in LN95R5, showing that Ru reduces at a lower temperature (∼175 °C), followed by a two-step reduction of Ni (∼200–285 °C). Despite this stepwise reduction, the resulting nanostructure is not a homogeneous alloy but a heterostructured bimetallic particle consisting of Ni matrices containing Ru-rich clusters. Oxidation induces partial reversibility, with Ru efficiently reincorporating into the perovskite lattice while a fraction of Ni persists as Ni 2+ oxidic species, indicating kinetically constrained reintegration. These results establish how synthesis and redox conditions shape the nanoscale architecture of exsolved multimetallic particles.