The exsolution of nanoparticles from perovskite precursors has been explored as a route to synthesize catalysts with sinter or coke resistance. The characteristics of these exsolved nanoparticles are highly dynamic depending on the redox nature of the environment to which they are subjected. To develop their properties for thermo-and electrocatalytic applications, it is necessary to track the states and behavior of exsolved catalysts with in situ and ex situ characterization. In this study, we conduct in situ X-ray absorption spectroscopy (XAS) along with ex situ scanning transmission electron microscopy high-angle annular darkfield (STEM-HAADF) and energy-dispersive X-ray spectroscopy analysis of the parent perovskite oxide precursor, LaFe 0.8 Ni 0.2 O 3 , as its structure forms bimetallic NiFe nanoparticles and evolves in oxidative, reductive, and dry methane reforming environments. We develop a theory that NiFe exsolution is a function of the reduction potential where LaFe 0.8 Ni 0.2 O 3 transforms to NiFe alloy supported on LaO x -LaFeO x . The Ni starts to exsolve at 268 °C, while most Fe exsolves at 700 °C. During dry methane reforming conditions, most of the Fe is oxidized by CO 2 during the reaction and re-enters the perovskite as LaFeO 3 , while Ni remains on the surface as nanoparticles in the metallic state. During the oxidative regeneration phase, most of the Fe re-enters the bulk perovskite phase, while Ni is partially regenerated with a small percentage oxidized to large NiO nanoparticles. This study sheds light on the exsolution and regeneration of bimetallic alloy nanoparticles and the influence of the reaction conditions on their catalyst performance.

Sorption-enhanced catalysts are bifunctional materials consisting of a heterogeneous catalyst affixed to a solid sorbent with a combined capacity to selectively capture and convert CO2 directly to value-added fuels and chemicals in the same reactor. The benefits of facile separation of CO2, directly from air or from flue gas, and conversion to chemical commodities is appealing for developing an integrated carbon capture and utilization scheme. The growth of this area is rapidly expanding with interest from catalysis, materials design, and life-cycle analysis researchers. However, the promise of sorption-enhanced catalysts is limited by their reduced thermal stability, CO2 capture capacity, and restricted product streams to C1 hydrocarbons. The prime issue is that the reaction conditions for the capture of CO2, regeneration of the sorbent, and utilization can be vastly different. It remains a challenge to optimize both the properties of the sorbent support material and the heterogeneous catalyst used. This perspective summarizes the current state-of-the-art for the properties of solid sorbents, heterogeneous catalysts, and the combined sorbent-enhanced catalysts for producing hydrocarbons from CO2. Lastly, the perspective discusses challenges and future areas for improving the performance and capture efficiency of sorption-enhanced catalysts.

The reforming of methane from biogas has been proposed as a promising method of CO2 utilization. Co‐based catalysts are promising candidates for dry methane reforming. However, the main constraints limiting the large‐scale use of Co‐based catalysts are deactivation through carbon deposition (coking) and sintering due to weak metal‐support interaction. We studied the structure‐function properties and catalytic behavior of Co/TiO2 and Co−Ru/TiO2 catalysts using two different types of TiO2 supports, commercial TiO2 and faceted non‐stoichiometric rutile TiO2 crystals (TiO2*). The Co and Ru metal particles were deposited on TiO2 supports using a wet‐impregnation method with the percentage weight loading of Co and Ru of 5% and 0.5%, respectively. The materials were characterized using SEM, STEM‐HAADF, XRD, XPS and BET. The catalytic performance was studied using the CH4 : CO2 ratio of 3 : 2 to mimic the methane‐rich biogas composition. Our results indicate that the addition of Ru to Co catalysts supported on TiO2* reduces carbon deposition and influences oxygen mobility. Co and Co−Ru catalysts supported on TiO2* has superior activity with the highest conversion of CO2 and CH4 of 34.7% and 23.5%, respectively. Despite the improved performance, the Co−Ru/TiO2* catalyst has limited stability due to the proliferation of nanoparticle growth and TiOx layers on the surface of the nanoparticles indicating the prevalence of the strong‐metal support interaction.

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