第二届中国化学链会议

CuFe₂O₄ is an emerging high-performance oxygen carrier for Chemical-looping combustion (CLC) is an emerging combustion technology, which is hailed as the most promising technology to reduce combustion-derived CO₂ emission. While CuFe₂O₄ oxygen carriers with minute structural difference could be largely divergent in the reactivity for CLC process, which seems not raise much concern by neither experimental nor computational studies. Herein, based on density functional theory (DFT) calculations, we compare the performance of three well-documented CuFe₂O₄ configurations as oxygen carriers in CLC process and relate the reactivity difference to their structural nuances. The reaction mechanisms of representative CLC reactants (i.e., CH₄, H₂, and CO) over different CuFe₂O₄ configurations are explored in-depth. DFT calculations indicate that among different CuFe₂O₄ configurations, the distribution, orientation and activity of O/Cu/Fe sites vary largely over the respective CuFe₂O₄(100) surfaces, thus affecting the adsorption and oxidation of CLC reactants. Fe atoms, especially in the configuration 3, are observed to exhibit higher exposure degree and afford lower steric hindrance to interact with CH₄ and H₂, thereby facilitating higher adsorption energies and lower dissociation energy barriers correspondingly. The distribution of low coordination O sites as well as the Fe-Cu synergistic effect are revealed to promote the dissociation reaction of both CH₄ and H₂. For the case of CO, O sites generally exhibit higher adsorbing capacity than Cu/Fe sites that can directly react with CO to produce CO₂. O sites in configuration 3 are observed with generally lower oxygen vacancy formation energy as well as steric hindrance, thus affording facile activation of CO. The structure-performance relationship revealed in this work is of positive significance to the design of high-performance spinel CuFe₂O₄ oxygen carriers.

chemical looping combustion,CuFe2O4 oxygen carries,Structure-reactivity relationship,DFT calculations