Simulation study on the reaction mechanisms of Fe-based oxygen carrier supported by CeO2 with CO
Chemical looping combustion technology is a new type of combustion technology with near zero carbon emission.Oxygen carrier plays the dual role of oxygen carrying and heat transfer in chemical looping combustion reaction.Improving the reaction performance of Fe-based oxygen carrier by tuning microstructure has been one of research focuses in the field of chemical looping technology.In this study,CeO2 was used as the active catalytic support to catalyze and tune of Fe-based oxygen carrier based on density functional theory.The elec-tronic structural characteristic parameters of CO adsorption,such as state density,adsorption energy,differential charge density,and acti-vation energy at the different sites of Fe2O3 clusters,were systematically analyzed by optimizing the constructed composite model.The re-sults show that the electrons of Fe2O3 clusters are transferred to CeO2(111)surface,and the binding energy is-3.92 eV,and Fe2O3 clus-ters can be bonded on the CeO2(111)surface stably.Density of states(DOS)analysis show that the p and d orbitals of Fe2O3 clusters af-ter loading migrate to the Fermi level at-8-0 eV,indicating that the adsorption is enhanced.The electrons in the p and d orbitals of Fe2O3 clusters decrease,the existing electrons transition to higher energy levels,and the electronic activity of Fe2O3 clusters increases.Therefore,the activation energies of CO molecules at three adsorption sites of Fe2O3 clusters in Fe2O3/CeO2 complex oxygen carrier de-crease.Furthermore,CeO2(111)enhances the adsorption of CO at the Fe top of Fe2O3 clusters,increasing the adsorption energy from-0.33 eV to-1.78 eV.Then the over-strong adsorption at the O top is weakened,and the adsorption energy is reduced from-2.69 eV to-2.32 eV,this also facilitates the subsequent release of CO2 molecules from the surface of Fe2O3 clusters,thus effectively tuning the overall adsorption effect of Fe2O3 clusters on CO.It provides theoretical guidance for the design,preparation,and optimal tuning of Fe-based oxygen carrier.
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