Effect of support on hydrogen generation over iron oxides in the chemical looping process.

FeO is recognized as an excellent oxygen carrier for its low cost and high oxygen capacity. However, pure FeO must be deposited on supports to ensure high reactivity and durability. Here, we proposed several FeO-based oxygen carriers using MgAlO, CeGdO, and ZrYO as supports and investigated their performance for chemical looping hydrogen generation. The support effect on chemical looping hydrogen generation performance was evaluated, and the fundamental insights were investigated in depth. FeO/CeGdO exhibited a superior performance regarding high hydrogen yield and stable trend over 20 cycles at 750 °C. However, hydrogen yield of FeO/ZrYO exceeded that of FeO/CeGdO at higher temperatures (850 °C). Characterizations show that CeGdO exhibits the highest oxygen vacancy concentration, which significantly improves the reduction and reoxidation reactions of FeO, thus leading to an enhanced hydrogen yield. However, the interaction between FeO and CeGdO contributed to the increase in Fe concentration, thus decreasing the oxygen capacity during the redox cycle and contributing to the declined hydrogen yield at higher temperatures. This work highlights the potential of CeGdO to be used as an effective support for FeO at mid-temperatures. We hope that the support effect in this work can be extended to design and select more active and durable oxygen carriers.