Ultrafast Flame Exsolution of High-Density Metal Nanoparticles on Perovskite Oxides

Exsolution of metal nanoparticles (NPs) is a powerful strategy for creating strongly attached catalysts for various energy-related applications, but the conventional exsolution methods based on thermal reduction are typically conducted at high temperatures for several hours to achieve sufficient NPs formation. Here, we introduce a new flame exsolution method that is exceptionally simple and rapid for decorating perovskite oxide surfaces with a high density of metal NPs under ambient conditions. By exposing perovskite oxides to a controlled fuel-rich methane-air flame (equivalence ratio, Φ = 1.45), we produced dense Ni NPs (∼500-550 μm⁻²) in just 1 min on both (La0.6Sr0.4)(Co0.2Fe0.8Ni0.05)O3-x (LSCF-5Ni) thin films and La0.43Ca0.37Ti0.94Ni0.06O3-x (LCTN) pellets. We further demonstrated that similar exsolution results were obtained for both perovskites using a common propane torch within 20 s, demonstrating the method's easy accessibility. This work establishes an ultrafast and transformative pathway to produce high-density metal NPs on perovskite oxides, overcoming the primary limitations of conventional exsolution techniques.