Hydrogen production from the methanol decomposition on the Pd(110) surface as catalyst considering the various possible reaction pathways: Theoretical study using DFT-D method

Abstract

Abstract The density of state (DOS) analysis was carried out for the two Pd(111) and Pd(100) surfaces previously studied and the Pd(110) surface which is used here to compare their reactivity and argue the choice of Pd( 110) as a catalyst in the present work. The investigation of the dehydrogenation and the adsorption mechanism of methanol on the Pd(110) surface has been performed by self-consistent periodic density functional theory with dispersion correction (DFT-D). Different adsorption sites of the relevant intermediates on the surface have been identified. It was found that CH3OH and CH2OH prefer to adsorb on the top site (t_ Pd), CH2O adsorb via O and C on the top site (t_ Pd), while CH3O, CHOH, CHO, and CO species adsorb on the bridge short site (bs_PdPd), COH and H on the hollow1 site (h1_Pd3). In addition, a complete reaction network comprising four reaction pathways was constructed and analyzed, which indicated that the initial cleavage of the C—H bond of CH3OH appears to be more favorable than the cleavage of the O—H bond on the Pd(110) surface from the point of view of activation barriers. It has been also shown that CH3OH→CH2OH→CH2O→CHO→CO is the most possible dehydrogenation pathway on Pd(110) surface. The remarkable differences in the activity and the predominant reaction pathway on Pd(100) and Pd(110) indicate that the dehydrogenation of methanol is sensitive to the orientation of the crystal planes (h k l).