Tailoring Surface Adsorption and Reactivity of Fullerene-Based Compounds: A Theoretical Probe into C₂–Gas–Fullerene Surface Interactions

Density functional theory investigations of palladium and nickel substituted fullerenes (C₅₉M; M = Pd/Ni) were carried out probing the changes in their surface adsorption potential. Structure and bonding in the proposed heterofullerenes were established with insights into metal–carbon bond character, stability, and adsorption potential. C₂‑gases were used as probe gases for adsorption tests. Adsorption of acetylene, ethylene, and ethane was studied with different sites over pure and heterofullerenes. Adsorption of acetylene was stronger than the adsorption of ethylene and ethane over C₆₀ with the bridge site sharing hexagonal rings being the energetically favored adsorption site. Surface modification of the fullerene molecule with a foreign metal enhanced the gas-substrate (C₂-heterofullerene) interactions. Enhanced surface interactions and differential adsorption behavior of different heterofullerenes made them potential candidates as selective acetylene hydrogenation catalysts. Free energy landscapes for hydrogenation of acetylene and ethylene over all three compounds were developed. The energy barriers for various elementary steps during hydrogenation were significantly smaller over the heterofullerenes when compared to those over C₆₀. Whereas substitution of either metals resulted in a reduction of activation barriers, the activation barriers for post-ethylene formation reactions were smaller over C₅₉Ni making C₅₉Pd a good selective acetylene hydrogenation catalyst

Adsorption of C2 gases over CeO2-based catalysts: synergism of cationic sites and anionic vacancies

The synthesis of novel and efficient catalysts for acetylene hydrogenation exhibiting high selectivity towards ethylene is important due to the presence of selective acetylene hydrogenation reaction in petrochemical processing. Since adsorption of C2 gases constitutes the primary step in catalytic hydrogenation and governs the selectivity of the catalysts, we have explored the C2-adsorption potential of reducible CeO2-based systems. The adsorption of C2-gases over CeO2-based materials was assessed using experimental in situ spectroscopic techniques and in silico theoretical studies based on density functional theory. The effect of Pd2+ substitution on adsorption was studied. The addition of Pd2+-ions was found to enhance the adsorption of the gases. Theoretical calculations provided insights into the modes of adsorption, adsorption energetics and reactant–catalyst interactions. The role of the presence of cationic substitution and anionic vacancies in strengthening the adsorption of gases was established. Pd-substituted reduced CeO2 showed activity for the adsorption of all C2 gases. On the basis of the aforementioned experimental and theoretical observations, the catalysts were tested for acetylene hydrogenation, and Pd-substituted CeO2 was found to be a good catalyst for the reaction with complete acetylene conversion observed below 100 °C.by Manjusha C. Padole, Bhanu Pratap Gangwar, Aman Pandey, Aditi Singhal, Sudhanshu Sharma and Parag A. Deshpand