https://doi.org/10.1016/j.fuel.2022.123420
“The mechanism of ICCM over Ru/CeO2-MgO was studied by in situ DRIFTS characterization using Ru/rod-CeO2-MgO catalyst with Ru/rod-CeO2 as the benchmark, as shown in Fig. 9. During the CO2 adsorption of Ru/CeO2-MgO, a set of peaks appeared and gradually increased, including the peaks at 1614 cm−1 (bidentate carbonates [58]) and 1815 cm−1 (carbonyl vibration of carbonates), which represented the CO2 adsorption on MgO by forming carbonates. The peaks belonging to CO2 adsorption can be saturated within 15 mins over Ru/CeO2-MgO combined materials. As for the key intermediates, we observed CO2 dissociation at the initial time of CO2 adsorption, including the peaks at 2037 cm−1 and 1993 cm−1 (linear or bridged Ru-CO [14], [59], [60], [61]). The dissociation of CO2 on Ru was fast and stable under Ar purge and vanished quickly under H2. With the introduction of H2, there is also a significant peak shift from 1614 cm−1 to 1582 cm−1(conjugated C-O/C = O of formats [14], [61]) and OCO peak at 1367 cm-1 [62], representing the possible formates reaction pathway on the surface of MgCO3. Ru/rod-CeO2 can also adsorb CO2 to form carbonates [63], which may be related to the oxygen vacancies on the surface. In short, there are mainly two reaction pathways in ICCM over Ru/CeO2-MgO, including CO2 dissociation on Ru and formates on MgCO3. The gradually increased CO2 conversion during cyclic ICCM over Ru/rod-CeO2-MgO might be attributed to the promotion of the formates pathway.”
“Fig. 9. In situ DRIFTS of ICCM over Ru/rod-CeO2-MgO and Ru/rod-CeO2.”