A mechanistic periodic DFT study of CH, CO, and OH dissociations in methanol: M-doped carbon nanotubes (M=Pt, B, Al, N, P) versus Pt(100), Pt(110) and Pt(111) surfaces

Abstract

• CO, CH, and OH dissociations in methanol are studied by using Pt(100), Pt(110), Pt(111), and doped CNT. • Dissociations are studied from both thermodynamics and kinetics points of view. • Theory shows that proposed SACs have less barrier energy for C−O dissociation compared to pure Pt surfaces. Periodic density functional theory is used to study adsorption and first step dissociation of methanol on M-doped carbon nanotubes (M = B, Al, Pt, N, and P) as a single atom catalyst (SAC). Data are compared with the adsorption and dissociation of methanol on Pt(100), Pt(110), and Pt(111). Only the first step of methanol dehydrogenation is investigated by considering three models of dissociations containing CH 3 + OH, CH 3 O + H, and CH 2 OH + H. The second model of dissociation is endothermic on all facets of Pt catalyst, but exothermic on B-, Al-, and Pt-doped carbon nanotube. The model of dissociation of CH 2 OH + H is more thermodynamically favorable on Pt(100), Pt(111), and Pt-doped carbon nanotube comparing to two other models. The most exothermic reaction belongs to the CH 3 + OH model on Al-doped carbon nanotube with -1.00 eV energy. Transition state calculations show that the barrier energy of C‒O dissociation on Al-doped carbon nanotube is 1.55 eV which is less than the barrier energies of C‒O dissociation on Pt(100), Pt(110), and Pt(111) which are 2.29, 2.45, and 1.96 eV. This shows that Al-doped carbon nanotube is a good candidate for alkylation catalyst. On the other hand B-doped carbon nanotube is a good non-metal catalyst for hydrogen production through O‒H dissociation.