Solar thermochemical CO2 splitting with doped perovskite LaCo0.7Zr0.3O3: thermodynamic performance and solar-to-fuel efficiency

Abstract

The research of thermochemical CO₂ splitting based on perovskites is a promising approach to green energy development. Performance evaluation was performed towards the doped perovskite LaCo_0.7Zr_0.3O₃ (LCZ-73) based two-step thermochemical CO₂ splitting process thermodynamically based on the experimentally derived parameters for the first time. The impacts of vacuum pump and inert gas purge to reduce oxygen partial pressure and CO₂ heating on the performance parameter η_{solar-to-fuel} have been analyzed. The results showed that at the P_O2 of 10⁻⁵ bar, non-stoichiometric oxygen δ increased by more than 3 times as the reduction temperature varied from 1000 °C to 1300 °C, however, no significant deviation of δ was observed between 1300 °C and 1400 °C. The reaction enthalpy ranged from 60 to 130 kJ mol⁻¹ corresponding to δ = 0.05–0.40. Comparing the abovementioned two ways to reduce the oxygen partial pressure, the η_{solar-to-fuel} of 0.39% and 0.1% can be achieved with 75% and without heat recovery with the CO₂ flow rate of 40 sccm under experimental conditions, respectively. The energy cost for CO₂ heating during the thermodynamic process as the n_CO2/n_LCZ-73 increases was obtained from the perspective of energy analysis. The ratio of n_CO2/n_LCZ-73 at lower temperature required more demanding conditions for the aim of commercialization. Finally, the ability of perovskite to split CO₂ and thermochemical performance were tested under different CO₂ flow rates. The results showed that high CO₂ flow rate was conducive to the production of CO, but at the cost of low η_{solar-to-fuel}. The maximum solar-to-fuel efficiency of 1.36% was achieved experimentally at a CO₂ flow rate of 10 sccm in the oxidation step and 75% heat recovery.