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A.H. Bork, E. Povoden-Karadeniz, S Schweiger, J.L.M. Rupp:
"Thermochemical solar to fuel conversion efficiency based on CALPHAD data for lanthanum manganite perovskites dobed with strontium and chromium";
Poster: 2016 MRS Spring Meeting & Exhibit, Phoenix, Arizona; 2016-03-28 - 2016-04-01.

Finding new strategies for transition away from dependence of fossil fuels is a global challenge of the 21st century. Two-step thermochemical production of syngas, is an energy technology utilizing solar power to convert water and carbon dioxide into syngas, an attractive renewable fuel that can replace fossil fuels. Recently, perovskites have attracted much attention due to impressive solar fuel yields surpassing state-of-the-art material ceria.1 Although higher yields can be obtained, it does not imply that it is the best choice for solar to fuel reactor. It is critical to compare the thermochemical fuel conversion efficiency, because it defines the actual useful chemical energy per input of solar energy.2, 3 Typically, this is calculated from oxygen nonstoichiometry equilibrium data derived from thermogravimetric measurements in the relevant temperature range, or extrapolations of data at lower temperatures. Performing experiments to test a few selected compositions is useful but time consuming and it does not give the best estimate of the thermochemical efficiency. We calculate thermochemical fuel conversion efficiency based on CALPHAD descriptions of defect chemistry of multi-component perovskites, based on critical review of all available experimental phase stability data. It is found that this defect chemistry model based on the weighted sum of optimized energies of various ionic compounds assembling the perovskite phase extrapolates well over the whole technologically relevant temperature and oxygen partial pressure range. Further, the thermodynamic properties are determined for a continuous variation of the doping concentration x, so a large compositional space can be tested. We compare and highlight advantages of this approach to previous predictions of thermochemical efficiency. The efficiency analysis is exemplified by using data on the perovskite composition La0.6Sr0.4Mn1-xCrxO3-δ. Finally, we discuss how the presented approach can be generalized to effectively screen other dopants and select the most efficient material for various operating conditions.