Toward the Compositional Optimization of Multicomponent Exsolved Metallic Nanoparticles from Perovskite Electrodes
Alfonso J. CARRILLO
Bio
Dr. Alfonso J. Carrillo holds a degree in Chemical Engineering from the University of Salamanca, a master’s degree in Renewable Energy from the University of León, and a Ph.D. in Chemical Engineering from Rey Juan Carlos University. After completing his doctoral research at IMDEA Energy, he held postdoctoral positions at ETH Zurich (Switzerland) and the Massachusetts Institute of Technology (USA), where he was an Eni-MIT Energy Fellow. He has received several awards and fellowships, including recognition as a Chemical Communications Emerging Investigator 2024, a Leonardo Grant from the BBVA Foundation, a Junior Leader Fellowship from the “la Caixa” Foundation, a Juan de la Cierva Fellowship, and a research grant from the Iberdrola Foundation.
He is currently a tenured scientist at the Spanish National Research Council (CSIC), based at the Institute of Chemical Technology (ITQ) in Valencia, where he conducts research as part of the Energy Conversion and Storage Group. His research focuses on the development of redox materials for energy applications, with a particular emphasis on thermochemical energy storage and renewable fuel production.
Abstract
The exsolution of metallic nanoparticles from perovskite oxides is a promising method for producing highly dispersed and stable catalysts through 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, managing the exsolution of multiple cations requires careful control of processing conditions and fine-tuning of the B-site composition. This is primarily due to the varying reducibility of each element (following Ellingham trends), which significantly influences the subsequent concentration of each constituent in the exsolved nanoparticle.
Our group has spent the last few years studying multicomponent exsolution using Sr₂Fe₁.₅Mo₀.₅O₆₋δ-based perovskites as a platform. First, because these materials serve as excellent electrodes for solid oxide electrochemical cells. Second, this class of perovskites can readily accommodate multiple cations substituting Fe at the B-site, facilitating the exsolution of multicomponent nanoparticles. We initially investigated 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 demonstrated excellent performance in CO₂ electrolysis, with high Faradaic efficiency and low polarization resistance. Here, we demonstrate that adjusting the gas atmosphere, temperature, and pressure allows for further control of nanoparticle composition. Notably, high-pressure exsolution (up to 100 bar) revealed a volcano-like dependence of both the extent of exsolution and the alloy composition on pressure. We also show that redox cycling under atmospheric pressure modifies surface chemistry, leading to Fe enrichment. Lastly, we explore temperature effects on Cu-Co-Fe-Ni exsolution, identifying conditions that favor the formation of Janus-type nanoparticles, primarily driven by the low miscibility of Cu and metallic Fe. Interestingly, these phase-separated Janus-type nanoparticles significantly alter the reversibility of exsolution in this system, leading to the formation of pyramidal NiO nanoparticles instead of complete redissolution.
Finally, we reveal how adjusting the composition of these multielemental exsolved nanoparticles (via phase separation or Fe enrichment) affects the catalytic properties of these materials, directing reactions toward targeted products. These results highlight the potential and versatility of multicomponent nanoparticle exsolution in (electro)catalytic processes for renewable fuel production.
Contact: Clément Nicollet (ST2E)
