a b s t r a c tSorption enhanced CO 2 methanation is a complex process in which the key challenge lies in the combined optimization of the catalyst activity and water adsorption properties of the zeolite support. In the present work, improved nickel-based catalysts with an enhanced water uptake capacity were designed and catalytically investigated. Two different zeolite frameworks were considered as supports for nanostructured Ni, and studied with defined operation parameters. 5Ni/13X shows significantly increased, nearly three-fold higher, operation time in the sorption enhanced CO 2 methanation mode compared to the reference 5Ni/5A, likely due to its higher water sorption capacity. Both catalysts yield comparable CO 2 conversion in conventional CO 2 methanation (without water uptake). Regeneration of the catalysts performance is possible via a drying step between methanation cycles under both reducing and oxidizing atmospheres; however, operation time of 5Ni/13X increases further after drying under air.

a This paper presents a proof-of-concept study and demonstrates the next generation of a "smart" catalyst material, applicable to high temperature catalysis and electro-catalysis such as gas processing and as a catalyst for solid oxide cells. A modified citrate-gel technique was developed for the synthesis of La x Sr 1À1.5x Ti 1Ày Ni y O 3Àd . This method allowed the synthesis of single phase materials with a high specific surface area, after the first calcination step at temperatures as low as 650 C. Up to 5 at% of nickel could be incorporated into the perovskite structure at this low calcination temperature. X-ray powder diffraction and microscopy techniques have proven the exsolution of nickel nanoclusters under low oxygen partial pressure. The amount of exsoluted nickel nanoparticles was sensitive to surface finishing, whereby much more exsoluted nanoparticles were observed on pre-treated and polished surfaces as compared to original ones. Increasing A-site deficiency leads to a larger number of nickel particles on the surface, indicating a destabilizing influence of the A-site vacancies on the B-site metal cations.Repetitive redox cycles prove that the nickel exsolution and re-integration is a fully reversible process.These materials working in a cyclic and repetitive way may overcome the drawbacks of currently used conventional catalysts used for high temperature systems and overcome major degradation issues related to catalyst poisoning and coarsening-induced aging.

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The p erovskite-type mixed oxide La 0.3 Sr 0.55 Ti 0.95 Ni 0.05 O 3−δ (LSTN) is demonstrated to exhibit the remarkable property of structural regeneration, where Ni can be reversibly exsoluted from the host perovskite lattice resulting in a regenerable Ni catalyst for solid oxide fuel cell anode applications. Results of catalytic tests for the water gas shift reaction and electrochemical investigations on a buttonsized fuel cell demonstrate the redox stability of LSTN, its potential application in solid oxide fuel cells, and its ability to recover catalytic activity completely after sulfur poisoning. Nickel segregation was characterized and quantified on powder samples by means of electron microscopy, X-ray diffraction, X-ray absorption spectroscopy, and temperature-programmed reduction−reoxidation cycles. Catalyst stability was much improved compared to impregnated Ni/La 0.3 Sr 0.55 TiO 3−δ and Ni/Y 0.08 Zr 0.92 O 2 anode materials. A full cell was tested under both open circuit voltage and polarized conditions, showing a stable cell voltage over redox cycles as well as periods of reverse potential and current overload. The area-specific resistance of the anode layer was as low as 0.58 Ω cm 2 at 850 °C. This allows LSTN to be applied in redox-stable solid oxide fuel cell anodes and reversible segregation of Ni to be exploited for fast recovery from sulfur poisoning.

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