Characteristics of dopant distribution and surface oxygen vacancy formation for modified Fe2O3 in chemical looping combustion

The modification of Fe2O3 oxygen carriers (OCs) by introducing foreign dopants is an important strategy to improve the reduction performance in chemical looping combustion. The 27 potential dopants in the periodic table were employed to systematically analyze the correlation between the dopant distribution and its property, and the influence mechanism of the dopant on surface oxygen vacancy formation for modified Fe2O3 by combining density functional theory (DFT) calculations and H-2-TPR experiment. It was found that atomic radius and valence of the dopant are two crucial factors for its distribution. In addition, the dopant could regulate surface oxygen vacancy formation energy (E-vac) of Fe2O3 by affecting the charge distribution of surface oxygen and surface structure. All the dopants with the valence lower than substituted Fe (+3) could lower the E-vac of Fe2O3. Among the 27 dopants, Li, Na, K, Rb, Cs, Mg, Ca, Ni, Cu, Zn, Ag, Au, La, Ce, Pb, Al, Ti, Cr, Mn and Zr could significantly decrease the Evac of Fe2O3 and were identified to be promising dopants for modification of Fe2O3 OCs in CLC technology, which was well corroborated by H-2-TPR experiments.