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 longterm 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 degrees 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.