Redox materials for thermo-chemical
water-splitting: cerium oxide defect structure
Materials to be used in concentrating solar-thermal processes are being developed in close co-operation with DLR’s institutes of Solar Research and Engineering Thermodynamics. Materials include porous and particulate absorbers and redox materials to be used for generation of future solar fuels (hydrogen, hydrocarbons) as well as high-temperature heat storage.
SiSiC is being investigated as material to be used in volumetric solar absorbers with special focus on efficiency and durability in desert-type environments. The deposition of desert dusts may impact light absorbtion as well as air permeation. Moreover, desert dusts of special composition can trigger thermo-chemical corrosion of absorber materials at high operation temperatures.
Materials for Generation of Solar Fuels
In the field of solar fuels we investigate thermo-chemical cycles using transition-metal oxides ("redox materials"). For hydrogen or CO generation redox materials are first reduced at high temperature to a lower oxidation state by release of oxygen. Re-oxidation is performed in presence of H2O vapor or CO2, where oxygen is “captured” from these process gases and remaining H2 or CO as fundamental components of synthetic fuels are released. Our research aims at improved redox materials such as doped cerium oxide in order to increase efficiency, reaction kinetics, and cyclic lifetime.
Thermal Storage Materials
Redox materials could also be used for thermo-chemical heat storage. Heat can be stored during the endothermic reduction and can be released during subsequent exothermal oxidation. Our research is currently focusing on mangenese oxide and other oxides of multi-valent cations. Besides maximum heat-storage capability and high reaction kinetics long-term cyclic stability is crucial for future application of such redox materials. Key parameters under investigation are phase composition, microstructure, porosity and shape of redox materials. The development of high-temperature heat-storage materials and processes is not only crucial for solar-thermal power plants but also interesting for storage and use of excess heat from industry.