Dopant screening of modified Fe2O3 oxygen carriers in chemical looping hydrogen production

Enhancing the deep reduction of Fe2O3 oxygen carriers (OCs) is a major challenge in the chemical looping hydrogen production (CLH) process. To solve this issue, the modification of Fe2O3 OCs by introducing foreign dopant is an effective strategy. Here, we propose a dopant screening scheme, where surface oxygen vacancy formation energy (E-vac) is defined as a descriptor for the reducibility of modified Fe2O3 OCs. Using density functional theory (DFT) calculations, we evaluated the 18 potential dopants, including 3 alkali metals (Li, Na, and K), 2 alkaline earth metals (Mg and Ca), 11 transition metals (Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, and Zr), and 2 rare earth metals (La and Ce). The results indicated that Li, Na, K, Mg, Ni, Cu, Zn, La, and Zr dopants, which not only significantly enhance the reduction reaction from Fe2O3 to Fe3O4 but improve the deep reduction from Fe3O4 to FeO, are screened as the promising candidates for modified Fe2O3 OCs in the CLH process. Our work provided an efficient approach for the initial screening of modified Fe2O3 OCs with enhanced deep reducibility.