High temperature endothermic reduction of metal oxides, which can liberate oxygen gas at achievable conditions, converts thermal energy to stored chemical energy. A subsequent re-oxidation step either recovers the stored energy as heat or utilizes it to drive other chemical reactions. If the re-oxidation step restores the material to its original state so that the two-steps can repeat indefinitely, the sequence of reactions constitutes a thermochemical cycle. Two related processes (reversibly re-oxidizing with oxygen or affecting bond breaking by re-oxidizing with CO2 and/or water) are somewhat analogous, the fuel production option is significantly more constrained by thermodynamics and hence subject to greater challenges to efficiency and cost. Nonetheless, both chemistries have been of increasing interest due to their potential for high efficiency utilization of the sun and economic competitiveness for clean energy and most recently as a role in getting to negative emissions and closing the carbon cycle.
This seminar will discuss opportunities, thermodynamic and kinetic requirements, and challenges presented by metal oxide thermochemistry and show recent progress towards developing materials, components, and systems for thermochemical energy storage, and CO2/H2O splitting.