Dissociation And Oxidation Mechanism Of Methanol On Al₁₂N₁₂ Cage:A DFT Study

In recent few years,the DMFC?direct methanol fuel cell?is considered to be an efficient and nonpolluting power source in virtue of its excellent characters,such as quick start-up in room temperature,environmental friendliness,abundant source as well as the high hydrogen-to-carbon ratio.The catalytic decomposition of CH₃OH is one of the crucial steps in DMFC,therefore an efficient catalyst to enhance the reaction is desirable.Among those DMFC anode materials,fullerene-like structures are drawing scientific researchers'increasing attention due to their specific physical and chemical properties with potential applications in many aspects.In this work,we selected fullerene-like Al₁₂N₁₂2 and Al₁₂N₁₂Pt nanocage as the direct methanol fuel cell's anode catalyst to simulate the decomposition and oxidation process of methanol.The density functional theory?DFT?has been used to investigate the methanol adsorption,decomposition and oxidation as well as the water adsorption and decomposition on the clean and Pt-encapsulated Al₁₂N₁₂2 cages.On the anode catalytic layer,methanol solution is mainly oxidized by water to form carbon dioxide,electrons and protons.The electrode reaction equation is as CH₃OH-6e^-+H₂O?6H⁺+CO₂.It is shown that platinum metal atom can be encapsulated within the Al₁₂N₁₂2 cage thus forming Pt-encapsulated Al₁₂N₁₂2 cage electrocatalyst.According to the reaction results,CH₃OH and H₂O both prefer to be adsorbed on the Al atom top site.Two dehydrogenation pathways have been presented.One pathway starts with O-H bond broken?pathway I?and the other starts with C-O bond broken?pathway II?.Calculated results show that O-H bond scission is the significantly favorable reaction pathway than C-O bond scission on the cage surface.Furthermore,the structures of the intermediates,transition states and products,the corresponding energy barriers and reaction energies are confirmed.The results also show that the adsorption energies and energy barriers of CH₃OH and H₂O dissociation are cut down slightly with the aid of the platinum atom.Nevertheless,Pt-encapsulated Al₁₂N₁₂2 cage makes the potential energy surface changes smooth than pure Al₁₂N₁₂2 cage.In conclusion,Al₁₂N₁₂2 and Pt-encapsulated Al₁₂N₁₂2 cages could be served as effective catalysts to take the hydrogen atoms off the methanol and oxidize the CO molecules into CO₂ molecules.We hope that the results of this study could be useful for designing and developing of catalyst materials.