(448g) Improving Fe2O3 Reactivity with CO and CH4 in Chemical Looping Systems By Low Percentage 1st-Row Transition Metal Dopants: A Theoretical and Experimental Work

Chemical looping (CL) technology, which includes chemical looping combustion (CLC) and gasification (CLG), is one of the most promising platform in the field of clean energy due to its capability in simplified inherent CO₂ capture and value-added chemical production. One crucial factor in dictating the success of a CL process is the reactivity of oxygen carriers. In the CL technology developed at The Ohio State University (OSU), iron oxide is employed as the active oxygen carrier due to its abundance and low cost. In this work, we focus on improving the reactivity of Fe₂O₃ with CO and CH₄ by using low percentage (1%) 1^st-row transition metal (TM) dopants. A systematic dopant screening strategy is developed via the combination of ab initio density functional theory (DFT) simulations and experimental validations conducted in TPR (temperature programmed reduction). Reaction pathways of CO and CH₄ oxidation on the most thermodynamically stable Fe₂O₃ (0001) surface with and without dopants and defects were investigated, and the rate-limiting steps (RLS) were identified. Descriptors that correlate the energy barrier of the RLS with different dopants were found. Our results demonstrate that copper is the most efficient dopant among 1^st-row TMs as it can lower the reduction initiation temperature with CO and CH₄ by 50 and 150 °C, respectively. Such a decrease in operating temperature can expand the operational matrix for the autothermal operation, and facilitate the development of CL processes.