Enhanced hydrogen production of Fe-based spinel by relay catalysis of Fe0 and Fe-Ov-Cr species in chemical looping H2O splitting

Chemical looping H₂O splitting is considered as a promising approach to produce hydrogen thanks to its lower energy consumption and carbon footprint compared with traditional steam reforming. Fe-based oxides have been paid much attention but suffer from inferior H₂ production rate and stability due to insufficient activation for H₂O. Herein, it was found that the introduction of Cr into MgFe spinel oxides (MgFe_xCr_2-xO₄, MFCO) could greatly increase the performance of H₂O splitting driven by CH₄ reduction with the highest peak H₂ production rate of about 4.65 mmol min⁻¹ g⁻¹, H₂ productivity of about 2.88 mmol g⁻¹ and good stability during multiple redox cycles for MFCO-46 (the atomic ratio of Fe and Cr of 2:3), which exceeded most of the state-of-the-art Fe-based oxides. This originated from the Cr doping promoting Fe⁰ nanoparticles exsolution by activating CH₄ and Fe-O_v-Cr species formation which relay catalyzed H₂O splitting and was favorable for the fast recovery of lattice oxygen converted.