ABSTRACT
Due to the increasing demands of new and renewable energy sources by utilising plant oils, uncovering the underlying physico-chemical phenomena at the atomic level responsible for the effective deoxygenation plays a vital role in improving the performance of well-known as well as in looking for the possible new catalysts. This study aims at investigating the adsorption and C-O bonds cleavage of methyl butanoate (MB) over MoS2-based catalyst with various loads of Ni promoters by using first-principles density functional theory (DFT). This study employs surface model that never been used by previous researchers for their investigations of adsorption and bonds cleavage on Ni promoted MoS2-based catalysts. The introduction of nickel into MoS2-based catalyst allows the surface charges when interacts with MB to redistribute in such a way that induces stronger Coulombic attractive forces. This in turn could result in a more stable adsorption configuration. However only in certain Ni-loads will results in the most stable adsorption. Nevertheless the most stable adsorption of MB occurs on M-edge configuration which consists of two Ni atoms, i.e. M-2-Ni-A with adsorption energy at about -2.96 eV. As a comparison, the adsorption energy of MoS2 with the absent of Ni, i.e. M-0-Ni is just -2.79 eV. Since there are three C-O bonds in MB, this study proposes three possible reactions for these bonds to cleave. By using CI-NEB method, the activation energies of those three reaction are calculated. It shows that the presence of Ni with appropriate load could promote C-O bond cleavage, especially in one reaction C-O bond is weaken considerably. Further evaluation on bond dissociation energies of the closest C-C bond to the catalyst surface, M-2-Ni-A shows better reactivity on C-C bond cleavage than M-0-Ni, disregarding of those three reaction routes.
