Chemical looping steam reforming of methane over Ce-doped perovskites.

• La 1- x Ce x FeO 3 (x = 0, 0.5, 1) catalysts with orthorhombic structure were designed and prepared. • A site Ce3+ substitution improved the surface reactivity in H 2 O splitting step. • La 0.5 Ce 0.5 FeO 3 exhibited high oxygen restoration kinetics in re-oxidation step. • A redox mechanism for La 0.5 Ce 0.5 FeO 3 in chemical looping was proposed. Chemical looping steam reforming of methane (CL-SRM) has emerged as an attractive pathway on H 2 O splitting for H 2 production. However, this process still faces a major challenge in efficiently producing H 2 with high redox kinetics and yields. In this paper, the promoting effects of Ce3+ substitution into LaFeO 3 redox catalysts on thermochemical H 2 O splitting as well as partial oxidation of methane are presented. An appropriate amount of Ce3+ substitution in A site of LaFeO 3 (La 0.5 Ce 0.5 FeO 3) promotes the lattice oxygen conversion rate in methane partial oxidation step and boosts the reaction kinetics in H 2 O splitting step by enhancing the surface water activation and lattice oxygen mobility of the perovskite. In the CL-SRM process, the perovskite is reduced into Fe0/(La 0.5 Ce 0.5) 2 O 3 and Fe0/(La 0.5 Ce 0.5)O 2- x phases in methane partial oxidation step and recovered to the original perovskite structure in H 2 O splitting step with simultaneous production of hydrogen, which maintains a reversible phase transformation during 100 redox cycles. As a result, the La 0.5 Ce 0.5 FeO 3 achieves high stability with the superior performance for syngas and hydrogen production. These findings provide the fundamental understanding on the synergy between the catalytic sites and enhanced lattice oxygen mobility for the promotion of H 2 O activation and hydrogen productivity in chemical looping process. [ABSTRACT FROM AUTHOR]