Fig. 1 Schematic illustration of two-step thermochemical H2O splitting cycle showing the thermal reduction of ABO3 to ABO3-δ via a high-temperature treatment generating (Step 1) and re-oxidation of oxygen deficient ABO3-δ to ABO3 in water splitting to produce H2 (Step 2)

Fig. 2 Experimental setup for two-step thermochemical H2O splitting test

Fig. 3 a XRD pattern, b SEM image (insert shows the high magnification), c TEM image and HRTEM image (top insets), d EDX mapping of La, Ca and Mn distribution of the LCMO-0.4 perovskite sample

Fig. 4 a O2, b H2 production curves for La1-xCa x MnO3 perovskites series with the Ca doping level from 0.2 to 0.8 in a two-step thermochemical H2O splitting cycle carried out between 1300 and 900 °C

Fig. 5 a O2 and H2 production amounts, b re-oxidation yield of La1-xCa x MnO3 perovskites with the Ca doping level from 0.2 to 0.8 in a two-step thermochemical H2O splitting cycle conducted between 1300 and 900 °C

Fig. 6 a H2 production curves, b summarized H2 production amounts of LCMO-0.4 sample at different re-oxidation temperatures

Fig. 7 a O2, b H2 evolution curves of CeO2 and LCMO-0.4 in the two-step thermochemical H2O splitting cycle carried out between 1300 and 900 °C

Fig. 8 a Six consecutive O2, H2 production profiles and b O2 and H2 yields and their corresponding ratio as a function of cycle number