Chemical-looping combustion (CLC) is a novel and promising
low-cost
CO2 separation technology. The development of an oxygen
carrier with high performance is the key to the successful application
of CLC. Since it is still challenging for experimental measurements
to acquire detailed information on the atomic mechanisms between the
oxygen carrier and fuels or impurities. Alternatively, theoretical
methods based on density functional theory (DFT) have become a powerful
tool to study the electronic and structural properties of materials,
as well as to clearly reveal the underlying microscopic mechanisms,
which is helpful to rationally design high-performance oxygen carriers.
Hence, the application of DFT in understanding the mechanisms for
oxygen carrier development during the chemical-looping process is
reviewed. The reactivity and detailed reaction mechanism of oxygen
carriers are summarized, and the interaction between various components
and the synergy in oxygen carriers are revealed. Particularly, the
influences of foreign components (e.g., inert supports and dopants),
adsorbate interaction, and surface structure on the reactivity of
oxygen carriers are comprehensively discussed. Most of the examples
discussed are mainly concerned with the reaction characteristics on
the oxygen carrier surfaces. DFT calculations performed to understand
and predict variations in reactivity from one oxygen carrier to another
are emphasized. Moreover, the DFT method can also be employed to evaluate
and screen oxygen carriers with appropriate properties including resistance
to sintering, selectivity for production, and so forth. Finally, tentative
future works on essential challenges and possible opportunities of
understanding chemical-looping technology based on DFT calculations
are preliminarily provided.