Modified CeO2 as active support for iron oxides to enhance chemical looping hydrogen generation performance

Chemical looping hydrogen generation (CLG) is a promising pathway that can offer both the high purity hydrogen as well as the efficient CO 2 capture capability. However, this process was significantly hindered by the lack of active oxygen carriers at relatively low temperatures. Mixed ionic-electronic (MIEC) supported iron oxides exhibit desirable redox performance for the improved oxygen-ion conductivity. In this work, we prepared several A x Ce 1-x O 2-δ (A = Gd, La; x = 0, 0.1, 0.3) supported Fe 2 O 3 for hydrogen production at 750 °C. It was shown that Fe 2 O 3 /Gd 0.3 Ce 0.7 O 2-δ shows the highest hydrogen generation performance and stability over 50 redox cycles. The reactivity follows the sequence of: Fe 2 O 3 /Gd 0.3 Ce 0.7 O 2-δ  > Fe 2 O 3 /La 0.1 Ce 0.9 O 2-δ  > Fe 2 O 3 /Gd 0.1 Ce 0.9 O 2-δ  > Fe 2 O 3 /La 0.3 Ce 0.7 O 2-δ . The fundamental investigation shows that the doping of rare earth (Gd, La) into CeO 2 contributes to the formation of oxygen vacancies , thus improving the lattice oxygen diffusion. The enhanced hydrogen generation performance attributes to the high lattice oxygen diffusion to improve the reactivity and inhibiting outward diffusion of Fe. The roughly linear relation between the oxygen vacancy concentration and chemical looping performance can be extended to predict the performance of oxygen carriers for other chemical looping applications, methane reforming, combustion, and ethane dehydrogenation , etc .