Perovskite oxides for application in thermochemical air separation and oxygen storage

Abstract

A materials screening of perovskites for oxygen storage applications yielding two promising materials, SrFe0.95Cu0.05O3−δ and Ca0.8Sr0.2MnO3−δ with outstanding performance.

Redox Behavior of Solid Solutions in the SrFe1‐xCuxO3‐δ System for Application in Thermochemical Oxygen Storage and Air Separation

“…An even distribution of Cu in EDX maps as well as the presence of a single phase in the XRD analysis is a strong indicator for the formation of a solid solution. [1] To increase the sample purity for more detailed studies, a slight Sr excess leading to a nominal starting composition of Sr 1.05 Fe 0.95 Cu 0.05 O 3-δ was applied. This evaluation, however, was not performed on single crystals but the cooled melt, and thus the composition measured with this method is not necessarily equal to the phase composition.…”

“…This evaluation, however, was not performed on single crystals but the cooled melt, and thus the composition measured with this method is not necessarily equal to the phase composition. Adapted from Vieten et al [1] Figure 2. To further evaluate the phase composition, X-Ray diffractograms were analyzed, showing no copper oxides for x < 0.25 (see Figure 3).…”

“…In a second step, these redox materials are re-oxidized using a gaseous oxidant. [1,4] This application is referred to as solar-thermochemical air separation, and its potential lies in the direct usage of concentrated solar radiation as a heat source to drive this chemical separation process. [2] Via this means, hydrogen for energy storage and conversion can be produced using solar energy, and syngas, a mixture of CO and H 2 , can be further processed to hydrocarbons and synthetic fuels using the Fischer-Tropsch process ("solar fuels").…”

“…Among these, perovskites constitute one of the largest groups of multinary oxides, as many different element combinations lead to stable perovskites. [1] This leads to an increase in the oxygen storage capacity under ambient air like conditions. This oxygen nonstoichiometry δ is dependent on the temperature T and oxygen partial pressure p O2 , and thus allows gradual reduction and oxidation of the perovskite in dependence of T and p O2 .…”

Redox chemistry of CaMnO3 and Ca0.8Sr0.2MnO3 oxygen storage perovskites

“…Out of all materials we investigated, Ca 0.8 Sr 0.2 MnO 3 showed the highest gravimetric oxygen storage capacity, whereas CaMnO 3 featured the highest redox mass change per Kelvin of temperature change in the studied temperature regime. 10 The synthesis of both materials has been reported in the literature. [11][12][13] Moreover, the redox properties and enthalpies of CaMnO 3 and calcium containing perovskites have been studied before.…”