Chemical looping process is a novel energy conversion scheme, in which its in-situ carbon capture and high efficiency could be realized without energy penalty. The performance of oxygen carriers is one of the key drivers to the versatility of chemical looping processes. Rational design of carrier materials and their innovative synthesis requires a thorough understanding of the fundamental interactions that govern the redox mechanism; therefore, a systematic atomic-level exploration for chemical looping processes would be essential. Oxygen carriers exhibiting the property of uncoupling oxygen offers the potential to effectively convert solid carbonaceous fuels, as is called the Chemical Looping with Oxygen Uncoupling (CLOU) process. Typical oxygen carriers with the CLOU ability are Cu-contained, Mn-contained, and Co-contained oxides. This study selects CuO, Mn2O3, and Co2O3 and other first row transition metal oxides NiO and Fe2O3 as the systems of study, using DFT (Density Functional Theory) calculations to investigate their electronic structures and d-orbital configurations. The unequally spin-orbit mixing of the populated d orbitals resulted in those compounds performing the property of uncoupling oxygen. It appeared charging ordering in the lattice structure of Mn2O3, while a Jahn-Teller effect was obviously indentified for the systems of CuO and Co2O3. These configurations led to the weaker overlap between dx2-y2 orbital and O-pz orbital, and consequently the stability reduction on the bonds between metal atoms and O atoms.

Investigation on the mechanism of oxygen uncoupling in chemical looping processes by the DFT calculation

256th National Meeting (2018)

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