Synthesis of uniform Fe₂O₃@Y₂O₃ yolk−shell nanoreactors as chemical looping oxygen carriers

Iron-based materials are extensively employed as oxygen carriers in chemical looping processes, but their long-term performance is often inhibited by sintering and agglomeration. Here, we developed a yolk–shell structured Fe₂O₃@Y₂O₃ oxygen carrier, with each unit consisting of a Y₂O₃ shell encapsulating a nano-sized Fe₂O₃ core. The Y₂O₃ shell could protect the redox-active cores from sintering, and the void between the yolk and the shell is capable of tolerating cyclic volume and phase changes. During the simulated chemical looping cycles at 600 °C, the Fe₂O₃@Y₂O₃ oxygen carriers exhibit a consistent oxygen carrying capacity of 3 wt% over 50 cycles, without any distinguishable structural deterioration. With rational structure optimization, the Fe₂O₃@Y₂O₃ oxygen carriers with porous shell could enhance the mass transfer across the shell and enable higher reaction rates. The satisfactory sintering resistance of the Fe₂O₃@Y₂O₃ nanostructure demonstrates the feasibility of employing well defined yolk–shell structured oxygen carriers for chemical looping applications.