DFT calculations of Ni/CeO2-CaO based ICCU-methanation

“DFT calculations further investigated the role of nickel on the selectivity of the overall process. Based on the HRTEM (Fig. 1), (1 1 0) lattice plane is the preferentially exposed surface of CeO2 nanorods. Therefore, a ceria (1 1 0) supercell structure with a single oxygen vacancy (Ov-CeO2(1 1 0)) was constructed and optimised, on top of which a sub-nanometer Ni active site was supported, as shown in Fig. 6. After optimisation, CO adsorption energies were calculated for both systems, revealing Eb of −0.23 eV and −1.88 eV on Ov-CeO2(1 1 0) and Ni/CeO2(1 1 0), respectively. The low CO binding strength to Ov-CeO2(1 1 0) reflects a high potential for spontaneous desorption, as observed by in-situ IR spectra that no obvious peaks assigned to the CO adsorption on CeO2 are observed (Fig. S18). This accounts for the selectivity of CO2 reduction over ceria nanorods (Fig. 4). With the deposition of Ni cluster, the binding strength of CO on Ni/CeO2(1 1 0) surface is significantly enhanced, which increases the likelihood of further reaction and accounts for the shift to methane for Ni doped ceria nanorods.”


Fig. 6. Top and side view of the optimized structures of (a) CeO2(1 1 0) with a O vacancy (Ov-CeO2(1 1 0)), (b) Ov-CeO2(1 1 0) with the adsorption of CO, (c) CeO2(1 1 0) supported Ni cluster (Ni/CeO2(1 1 0)) and (d) Ni/CeO2(1 1 0) with the adsorption of CO. The yellow, red, grey and blue balls represent the Ce, O, C and Ni atoms. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)”

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