Fuel production capacity and DFT analysis of cation modified perovskites for enhanced thermochemical CO2 dissociation

Abstract

Solar thermochemical redox splitting of CO₂ using perovskite oxygen carriers in two-step cycles is a promising method for sustainable fuel production. In this study, a series of 23 potential perovskite candidates for CO production are designed, synthesized, and tested under the same experimental conditions. The material stability and the lattice structure are validated using Goldschmidt's tolerance factor and powder X-ray diffraction. For the reduction step, the high proportion of divalent cations (Sr²⁺/Ba²⁺/Ca²⁺) in the A site promotes oxygen transfer, and the maximum oxygen yield reaches 386 μmol g⁻¹ (δ = 0.164) for Gd_0.6Ca_0.4MnO₃. DFT calculation results indicate that the multi-cationic doping in La_0.5Sr_0.2Ba_0.15Ca_0.15MnO₃ shows a smaller energy barrier for oxygen transfer compared with the single A-site doping in La_0.5Sr_0.5MnO₃, with an oxygen vacancy formation energy of 2.91 eV per (O atom), and it offers the most favorable CO yields of 225 and 227 μmol g⁻¹ in two consecutive cycles. The designed La_0.25Gd_0.25Sr_0.25Ca_0.25MnO₃ further decreases the oxygen vacancy formation energy to 2.57 eV per (O atom). Based on the reaction rate analysis, the presence of B-site doping cations, such as in La_0.6Sr_0.4Mn_0.75Zr_0.25O₃ and La_0.5Sr_0.5Mn_0.8Ce_0.2O₃, increases the maximum oxidation rate, and the A-site multi doping of perovskites allows maintaining high CO production rates during the oxidation process. This work leverages tunable perovskite redox properties for enhanced CO production performance through DFT and thermochemical performance analysis, providing feasible guidance to promote CO₂ splitting by an active cation doping strategy.