Activation and Reactivity of Iron Oxides as Oxygen Carriers for Hydrogen Production by Chemical Looping

We report the activation principle, the different forms of activated oxygen carriers, and the optimal activation method for iron-based oxygen carriers. The activation of an oxygen carrier is commonly referred to as the enhancement of the oxygen transfer capacity of an oxygen carrier by repeated reduction and oxidation reactions, which is mainly attributed to enhanced intraparticle ionic/gaseous diffusivity over the support material. Accurate knowledge of the activation process for an oxygen carrier is a key issue in the development of particles and optimization of a chemical looping system. In this study, we found that two key factors, the interaction between iron oxide and the support as well as the localized hematite-lower oxides stress, are fundamental reasons for the activation of iron-based oxygen carriers. The dispersion of the iron oxide in the activated particles was determined by the iron oxide–support interaction. The larger the localized stress applied at the interface between the hematite and ...