Reverse water-gas shift chemical looping using a core-shell structured perovskite oxygen carrier

Reverse water-gas shift chemical looping (RWGS-CL) offers a promising means of converting the greenhouse gas of CO₂ to CO because of its relatively low operating temperatures and high CO selectivity without any side product. This paper introduces a core-shell structured oxygen carrier for RWGS-CL. The prepared oxygen carrier consists of a metal oxide core and perovskite shell, which was confirmed by inductively coupled plasma mass spectroscopy (ICP-MS), XPS, and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) measurements. The perovskite-structured shell of the prepared oxygen carrier facilitates the formation and consumption of oxygen defects in the metal oxide core during H₂-CO₂ redox looping cycles. As a result, amounts of CO produced per unit weight of the core-shell structured oxygen carriers were higher than that of a simple perovskite oxygen carrier. Of the metal oxide cores tested, CeO₂, NiO, Co₃O₄, and Co₃O₄-NiO, La_0.75Sr_0.25FeO₃-encapsulated Co₃O₄-NiO was found to be the most promising oxygen carrier for RWGS-CL, because it was most productive in terms of CO production and exhibited long-term stability.