Study On Hydrogen Production And Hydrogen Production From Chemical Chain Of Cerium And

Hydrogen is a clean, renewable energy and hydrogen fuel cells have broad application prospects. In the Early 20th century, the concept of chemical chain is introduced to reaction of hydrogen in the Steam-Iron Process. The net reaction in the hydrogen fuel cells is the redox of iron:Fe3O4+4H2â†'3Fe+4H2O (chemical H2 storage) and 3Fe+4H2Oâ†'Fe3O4+4H2 (H2 recovery). However, iron oxide sample without any pro-moters was deactivated quickly over numerous cycles due to the sintering of Fe3O4 and/or iron metal. Therefore, various metals or metal oxides termed as promoters, are added into Fe2O3 in order to improve their redox performances.The chemical hydrogen storage (hydrogen reduction) and production (water splitting) behaviour of Fe based Fe2O3-CeO2 mixed oxide oxygen carriers prepared by chemical precipitation method were investigated. The change of structure and species compositions of materials and redox properties has been investigated by means of activity tests and measurements including XRD, H2-TPR, H2O-TPO, XPS and SEM. The Fe2O3-CeO2 mixed oxide oxygen carriers for the storage, transport and supply of hydrogen to PEFC vehicles is feasible. At last reaction mechanism in this process was discussed with the help of modern detecting technologies.H2O-TPO experiments over reduced oxides showed that Fe-Ce mixed oxides could split water to produce hydrogen at a lower temperature and complete in a shorter time. The results of H2-TPR experiment for fresh and 10th Fe2O3-CeO2 mixed oxide oxygen carriers suggested that Ce addition could reduce hydrogen reduction temperature, while sintering with different level happened to all samples resulting in a decline of H2 consumption and increment of high temperature reduction peak. Comparing with fresh samples, the results of XRD and XPS for recyled samples suggested that new phase of Fe3O4 and CeFeO3 turned to be the main phases, and good redox properties was ascribed to the co-existence of Fe3O4 and CeFeO3, while the production of hydrogen was only determined by the content of Fe3O4.The successive redox cycles were carried out over Fe2O3-CeO2 mixed oxide oxygen carriers at 750 ℃. It kept a stability and activity for the hydrogen production at the condition of serious agglomeration of the materials. FeCe30 treated by 10 redox cycles maintained a constant hydrogen production rate twice more than that of fresh FeCe30, while the production of hydrogen and hydrogen production rate in FeCe20 with relatively shorter time is nearly twice more than that of single Fe2O3 and its hydrogen storage capacity was up to 2.71 wt%.High temperayure in favor of producting hydrogen, the time of hydrogen production for FeCe20 with 8min is shorter than pure Fe2O3 with 15min in the successive redox process at 750 ℃The combined results of those properties showed that althoug sintering of materials could not be prevented and activation energy can not be reduced, CeO2 addition in Fe2O3 promoted the hydrogen production performance and stability for the chemical-looping hydrogen storage and production.Through four redox reaction, only 35 wt% Fe in Fe2O3 can continue to participate in the redox reaction, which is lower than 92 wt% Fe in Fe2O3-CeO2 oxygen carriers.