Kyle M. Allen

Effects of Dopant Metal Variation and Material Synthesis Method on the Material Properties of Mixed Metal Ferrites in Yttria Stabilized Zirconia for Solar Thermochemical Fuel Production

Mixed metal ferrites have shown much promise in two-step solar-thermochemical fuel production. Previous work has typically focused on evaluating a particular metal ferrite produced by a particular synthesis process, which makes comparisons between studies performed by independent researchers difficult. A comparative study was undertaken to explore the effects different synthesis methods have on the performance of a particular material during redox cycling using thermogravimetry. This study revealed that materials made via wet chemistry methods and extended periods of high temperature calcination yield better redox performance. Differences in redox performance between materials made via wet chemistry methods were minimal and these demonstrated much better performance than those synthesized via the solid state method. Subsequently, various metal ferrite samples (NiFe2O4, MgFe2O4, CoFe2O4, and MnFe2O4) in yttria stabilized zirconia (8YSZ) were synthesized via coprecipitation and tested to determine the most promising metal ferrite combination. It was determined that 10 wt.% CoFe2O4 in 8YSZ produced the highest and most consistent yields of O2 and CO. By testing the effects of synthesis methods and dopants in a consistent fashion, those aspects of ferrite preparation which are most significant can be revealed. More importantly, these insights can guide future efforts in developing the next generation of thermochemical fuel production materials.

SYNTHESIS AND ANALYSIS OF COBALT FERRITE IN YSZ FOR USE AS REACTIVE MATERIAL IN SOLAR THERMOCHEMICAL WATER AND CARBON DIOXIDE SPLITTING

This paper reports the synthesis, characterization and evaluation of different weight loadings of cobalt ferrite (CoFe2O4) in 8 mol% yttria-stabilized zirconia (8YSZ) via the co-precipitation method. Prepared powders were calcined at 1350 °C for 36 hours and 1450 °C for 4 hours in air. These powders were then formed into a porous structure using sacrificial pore formation via oxidation of co-mixed graphite powder. These formed structures obtained were then characterized using thermogravimetric analysis (TGA), X-ray diffraction (XRD), high temperature X-ray diffraction (HT-XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Brunauer-Emmett-Teller (BET) surface area analysis was performed on the most promising of the structures before being subjected to 50 thermal reduction-CO2 oxidation (redox) cycles using TGA. Together, these results indicate that CoFe2O4-8YSZ can provide a lower reduction temperature, maintain syngas production performance from cycle to cycle, and enhance utilization of the reactive material within the inert support in comparison to iron oxide only structures.Copyright