Comparative Evaluation of Various ABO3 Perovskites (A = La, Ca, Sr; B = Mn, Fe) as Oxygen Carrier Materials in Chemical Looping Hydrogen Production

This study comparatively evaluates the performance of ABO3 perovskite materials (A = La, Ca, Sr; B = Mn, Fe) as oxygen carriers in three-step Chemical Looping Hydrogen (CLH) technology, focusing on redox behavior, oxygen transport capacity, hydrogen production, and selectivity under controlled pulse-mode conditions. The redox behavior of the materials is analyzed in relation to their defect chemistry. Perovskites such as (La1−xCax)MnO3, (La1−xSrx)MnO3, and (La0.6Ca0.4)(Mn1−xFex)O3 were synthesized via wet chemical methods and tested in chemical looping cycles. Doping A-site cations with Ca or Sr enhanced oxygen delivery capacity by more than 100% upon reduction with CH4 when dopant content (x) increased from 0 to 0.5. However, H2 selectivity decreased from 52% to 2.5% for (La1−xCax)MnO3 and from 46% to 14% for (La1−xSrx)MnO3 under the same conditions. In contrast, substituting Mn with Fe significantly improved hydrogen production, particularly in LaFeO3, which exhibited the highest hydrogen selectivity and yield. At 1000 °C, LaFeO3 produced nearly 10 mmol H2 g−1, with 80% generated during the reduction step at 99.9% selectivity and the remaining 20% during the water-splitting step at 100% selectivity. These results are linked to the extent of B-site cation reduction reactions (i) B4+ → B3+, which facilitates complete fuel oxidation and (ii) B3+ → B2+, which leads to partial fuel oxidation. The reverse of (ii) also contributes to H2 production during water splitting. Additionally, the study assesses the materials’ microstructure and stability over prolonged cycles. The findings highlight Fe-based perovskites, particularly LaFeO3, as promising candidates for CLH applications, emphasizing the need for structural and compositional optimization to enhance hydrogen production efficiency.