Redox Performance of Cu-Doped Fe2O3/Al2O3 as Oxygen Carriers for Chemical Looping Hydrogen Production

Chemical looping hydrogen (CLH) production, or hydrogen production combined with CO2 capture, is becoming an emerging alternative technology that has attracted much attention. Iron-based oxygen carriers were most widely used in CLH. In this study, bi-active component composite metal oxides with Cu-doped Fe2O3/Al2O3 were synthesized. The oxygen carriers were characterized using different methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET), and their redox and cycle properties in the CLH process were investigated. The results showed that copper doping enhanced the activities of iron-based oxygen carriers, but excessive copper would reduce their reactivity due to melting and agglomeration. Hydrogen temperature-programmed reduction (H-2-TPR) analysis, fixed-bed experiments, and density functional theory (DFT) calculations all confirmed that Cu promoted the deep reduction of Fe2O3. Among them, the oxygen carrier doped with 1 wt % CuO was the most suitable material for CLH, where H-2 yield was the highest and sustained in a high and stable level in multiple redox cycles.