The exsolution of metallic nanoparticles from perovskite oxides is a promising route to obtain highly dispersed and stable catalysts via annealing in H₂-containing atmospheres. These nanoparticles remain anchored to the oxide surface, preventing sintering and enhancing resistance to carbon deposition, which leads to superior long-term catalytic performance compared to conventional noble metal-supported systems. Moreover, compositional tuning of the host oxide enables the controlled exsolution of alloy nanoparticles with unique electrocatalytic properties. However, dealing with the exsolution of multiple cations requires careful control of processing conditions and fine tuning of B-site composition. This is mainly due to the different reducibility that each element presents (following Ellingham trends) that, afterward,highly influence the concentration of each constituent in the exsolved nanoparticle.

Our group has devoted the last years to the understanding of multicomponent exsolution using as platform Sr₂Fe_1.5Mo_0.5O_6-δ based perovskites. First, because these materials are excellent electrodes for Solid Oxide Electrochemical cells. Secondly, this perovskite class can easily allocate multiple cations substituting Fe in the B-site, facilitating the exsolution of multicomponent nanoparticles. We initially investigate the exsolution of Ni-Co-Fe multicomponent alloys. By optimizing the microstructure and fine-tuning the exsolution treatment parameters, we achieved functionalization with ternary alloy nanoparticles (~10 nm) that previously showed excellent performance in CO₂ electrolysis, with high Faradaic efficiency and low polarization resistance.¹ Here, we demonstrate that adjusting gas atmosphere, temperature, and pressure allows further control of nanoparticle composition. Notably, high-pressure exsolution (up to 100 bar) revealed a volcano-like dependence of both exsolution extent and alloy composition on pressure.² We also show that redox cycling under atmospheric pressure modifies surface chemistry, leading to Fe enrichment.³ Lastly, we explore temperature effects on Cu-Co-Fe-Ni exsolution, identifying conditions that favor the formation of Janus-type nanoparticles, mainly affected by the low miscibility of Cu and metallic Fe. Interestingly, these phase-separated Janus-type nanoparticles greatly alter the reversibility property of the exsolution in this system, leading to the formation of pyramidal NiO nanoparticles instead of total redissolution.⁴

Finally, we reveal how the compositional tuning of these multielemental exsolved nanoparticles (via phase separation or Fe-enrichment) affects the catalytic properties of these materials, directing reactions to targeted products. These results highlight the potential and versatility of multicomponent nanoparticle exsolution in (electro)catalytic processes for renewable fuel production.