Development of a copper doped iron-based oxygen carrier for hydrogen production via mid-temperature chemical looping

Abstract

Chemical looping reforming (CLR) offers a promising approach for low-carbon hydrogen production by integrating fuel conversion with inherent CO₂ separation. In this study, iron-based oxygen carriers doped with nickel and copper were synthesized to improve reactivity and cyclic stability. Structural characterization via X-ray diffractometer (XRD) and energy-dispersive X-ray spectrometer (SEM/EDS) confirmed the formation of active phases including NiFe₂O₄ and CuFe₂O₄, which have homogeneous elemental dispersion and nanostructured morphologies. Temperature programmed reduction experiments in TGA revealed that Ni doping enhances reaction rates, while copper doping lowers the reduction temperature. Among the synthesized carriers, 1 wt%Cu–20NiFe exhibited the best overall performance in terms of methane conversion (82.45 %), hydrogen yield (74.40 mL/g_OC), and carbon monoxide yield (22.04 mL/g_OC) at 600 °C. Steam-assisted CLR experiments show that water significantly improved H₂ production, and appropriate steam flow could maximize hydrogen yield while suppressing carbon deposition. Long-term redox cycling (200 cycles) verified the structural integrity and oxygen transfer stability of 1 wt%Cu–20NiFe. X-ray photoelectron spectroscopy (XPS) analyses across different reaction stages confirmed the cyclic migration of lattice oxygen and complete regeneration of the oxygen carrier. This work demonstrates that micro-doped Cu in Ni–Fe-based oxygen carriers effectively enhances CLR hydrogen production, providing a foundation for further scale-up and integration in chemical looping hydrogen systems.