Beyond-Equilibrium Redox-Mediated Reverse Water–Gas Shift with La _{1– <i>x</i>} Sr _<i>x</i> Cr _<i>y</i> Mn _{1– <i>y</i>} O ₃ _–δ Perovskite Oxides

The reverse water gas shift (RWGS) reaction (CO2 + H2 → CO + H2O) can be used to activate CO2 with H2 to produce CO, a useful intermediate for the production of fuels and chemicals from CO2. The RWGS reaction can be implemented as a redox-mediated process, in which the RWGS reaction is split into two half-reactions: the reduction and oxidation of a solid metal oxide material. The thermodynamic properties of this material must allow (a) the conversion of the reactants to the product gas in high yield and (b) a large amount of oxygen to be transported between the two half-reactions. Here, we investigate the suitability of the La1–xSrxCryMn1–yO3–δ family of perovskite-type oxide materials for this application and explore the effect of the composition of the material on the thermodynamic properties and performance in the redox-mediated RWGS process. Six different compositions with varying degrees of Sr and Cr substitution were synthesized, and their thermodynamic properties were investigated using thermogravimetry and subsequent electronic defect modeling. The resulting model parameters were used to predict the material performance through simulations of the redox-mediated RWGS process. A higher Mn content at the B site of the perovskite oxide was demonstrated to substantially promote oxygen transport. Of the investigated materials, La0.75Sr0.25Cr0.25Mn0.75O3–δ exhibited the highest predicted oxygen transport of 0.757 ± 0.015 wt % @ T = 650 °C.