Theoretical Study of The Catalytic Effect Of TM-C۴H۴ And TMC۵H۵(TM = Cr, Ti, V, Sc) On the Activation Of O۲ At The Cathode AndCH۳OH At The Anode In “CH۳OH-O۲″ Fuel Cell Via DFT ComputationalMethod

The study of the interaction of oxygen molecule with organometallic compounds containing transitionmetals has always been an interesting subject for research, as the O۲ activation by them is a measure ofthe efficiency of organometallic catalysts. This study examined the catalytic effect of someorganometallic compounds containing transition metals with the general formula of TM-CmHm onincreasing the reaction rate of “methanol-oxygen” fuel cell using the method of density functionaltheory (DFT) and PW۹۱ method as well as the basis set of ۶-۳۱G(d) (TM represents each of Sc, Ti, Vand Cr and m is equal to ۴ or ۵). The structures of the mentioned compounds were optimized by thenatural bonding orbital calculations (NBO). Then, the diagrams of the density state (DOS) were plottedfor them and afterward, gap energy (Eg), chemical hardness (η) ،chemical potential (μ) andelectrophilicity (ω) were calculated in each case. The Eg and η of ScC۵H۵ were smaller than that ofthe others, indicating greater reactivity. Theoretical calculations showed that each of the TMs in TMCmHmhad a partial negative electric charge, which was higher in ScC۵H۵ than in others causinghigher chemical activity. The adsorption energies of O۲ and CH۳OH were calculated and reported oneach of the TM- CmHm. The adsorption energy of O۲ and CH۳OH on ScC۵H۵ was more negativethan that of the other TM-CmHm used. This confirms that the compound had a greater efficiency andability to play a catalytic role in the “oxygen - methanol” fuel cell. The results showed that the bondlength of O=O increased by about ۲۴% on average due to its adsorption on ScC۵H۵. The O-H bondlength was significantly increased in response to the methanol adsorption process onScC۵H۵. Increasing the bond length caused instability of the bond and raising its chemical activity andreactivity. The adsorption kinetics of each of O۲ and CH۳OH on ScC۵H۵ were also studied by the above-computational method. The potential energy variation of the “adsorbate/adsorbent” system interms of reaction coordinate (bond length of O=O or O-H) in each case was evaluated with a onetransition state observed in e ach case.