Sr2Fe1.5Mo0.5O6-δ double perovskite for chemical-looping hydrogen production from water splitting

Chemical-looping water splitting represents a promising route for efficient and sustainable hydrogen production. In this work, H 2 generation was enhanced by engineering the B-site of SrFeO 3 -based perovskites (SFO) through Mo substitution (SFMO), yielding structurally stable oxides with improved redox properties. These materials were evaluated in CO-assisted chemical-looping water-splitting cycles inspired by the water-gas shift process. The Mo-doped double perovskites exhibited superior redox performance, absence of crystallographic transitions, resistance to morphological degradation, and stable operation over at least 24 consecutive cycles. A comprehensive parametric study was conducted—exploring reaction temperature, gas flow rates, and mass loading—to identify suitable operating conditions and extract data for kinetic modeling. To gain mechanistic insight into the water-splitting step, controlled H 2 -assisted reduction experiments were performed for transient kinetic analysis. The transient redox kinetic model developed revealed that, in materials with high oxygen diffusion rates, water splitting is governed by thermodynamics (i.e., equilibrium-limited) rather than reaction kinetics. Regarding the water splitting capacity, SFMO exhibited a H 2 production of ∼14 mL/g for 24 cycles, whereas it was 4.3 mL/g for SFO. This is a 3-fold increase in the H 2 yield, indicative of the benefits of Mo-incorporation on the water splitting reaction. These findings provide valuable insights into the development of robust oxygen carriers for scalable hydrogen production in chemical-looping systems.