Solar thermochemical CO(2) splitting with doped perovskite LaCo(0.7)Zr(0.3)O(3): thermodynamic performance and solar-to-fuel efficiency

The research of thermochemical CO(2) splitting based on perovskites is a promising approach to green energy development. Performance evaluation was performed towards the doped perovskite LaCo(0.7)Zr(0.3)O(3) (LCZ-73) based two-step thermochemical CO(2) 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 CO(2) heating on the performance parameter η(solar-to-fuel) have been analyzed. The results showed that at the P(O(2)) 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 CO(2) flow rate of 40 sccm under experimental conditions, respectively. The energy cost for CO(2) heating during the thermodynamic process as the n(CO(2))/n(LCZ-73) increases was obtained from the perspective of energy analysis. The ratio of n(CO(2))/n(LCZ-73) at lower temperature required more demanding conditions for the aim of commercialization. Finally, the ability of perovskite to split CO(2) and thermochemical performance were tested under different CO(2) flow rates. The results showed that high CO(2) 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 CO(2) flow rate of 10 sccm in the oxidation step and 75% heat recovery.