An Investigation of Nonstoichiometric Oxides for Solar-Driven Thermochemical Fuel Production

Citation

Ignatowich, Michael Joseph (2017) An Investigation of Nonstoichiometric Oxides for Solar-Driven Thermochemical Fuel Production. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z92805PM. https://resolver.caltech.edu/CaltechTHESIS:06052017-162306037

Abstract

In order to realize energy independence and substantially combat global climate change, renewable and sustainable energy technologies must be developed. Solar energy is the most readily abundant, and if converted into a chemical fuel, could be stored and transported easily. Solar-driven thermochemical cycling is a method of chemical fuel production that shows great promise, but current state-of-the-art systems have very low efficiencies. This work discusses new reactor designs and cycling techniques using nonstoichiometric oxides that will enable more efficient solar to fuel energy conversion. Practical aspects of the reactor design are explored – specifically, thermochemical expansion of the reactive oxide, and morphologies aimed at enhancing the reaction kinetics. Additionally, doped fluorite- and perovskite-structured materials are evaluated for thermodynamic behavior and in-situ thermochemical cycling performance. Oxide morphology and new doped compounds show little improvement over previously established neat ceria due to thermodynamic limitations. The thermodynamic limit is explored in new reactor geometries and is shown to demonstrate significantly more efficient fuel production. Finally, different nonstoichiometry thermodynamics are explored to provide guidance for further material exploration, as well as applicable methodologies.

Thesis Files