Ni promoted Fe-CaO dual functional materials for calcium chemical dual looping.

• Calcium looping and chemical looping are isothermally integrated for CO 2 capture and CO generation. • Ni promoted Fe-CaO achieves effective and stable cyclic calcium chemical dual looping. • Ni promoted Ca 2 Fe 2 O 5 plays as the oxygen carrier to achieve the in-situ chemical looping. • Ca 2 Fe 2 O 5 improves the calcium looping stability by acting as a thermally stable physical barrier. • Steam or air purge after hydrogenation is effective to avoid CO generation in carbonation. Reverse water–gas shift reaction using renewable H 2 is a promising route for CO 2 upgrade, however, it is restricted by the equilibrium. The chemical looping reverse water–gas shift reaction using oxygen carriers (i.e. Fe) has proven a more effective CO 2 utilization process to produce CO. However, CO 2 with high purity is needed to obtain concentrated CO. Herein, we propose a calcium chemical dual looping using one-pot sol–gel synthesized Ca-Fe dual functional materials (DFMs). The CO 2 in the exhaust gas (∼10% CO 2) can be captured and transformed into carbonates and then in-situ converted into CO through continuous chemical looping in H 2 atmosphere. This process avoids CO 2 enrichment, storage and transportation and simultaneously realizes efficient CO 2 conversion. The Ca-Fe DFMs possessed significantly improved catalytic efficiency (enhanced real-time CO generation rate) compared to CaO. It is found that Ni 1 Fe 9 -CaO could optimally achieve 11.3 mmol g DFM −1 CO yield, 82.5% CO 2 conversion and 99.9% CO selectivity at 650 °C. Notably, Ni 1 Fe 9 -CaO displayed high CO 2 conversion (>80%) and CO selectivity (>99.9%) during the cycle tests and possessed enhanced stability in relation to CO yield after 10 cycles (20.9% and 35.5% decrease for Ni 1 Fe 9 -CaO and CaO, respectively). Herein, Ca 2 Fe 2 O 5 plays two roles: acting as an oxygen carrier for in-situ chemical looping to produce CO and a thermally stable physical barrier to retard the sintering of CaO. It is noted that Fe-related species could be reduced into the metallic state at the end of hydrogenation, resulting in CO formation in the following CO 2 capture process. [ABSTRACT FROM AUTHOR]