First-principles study of CO catalytic oxidation on Pd-doped single wall boron nitride nanotube

The carbon monoxide (CO) catalytic oxidation reaction is a model reaction which is important in serials of technical and industrial applications. In this study, density functional theory (DFT) is employed to explore the catalytic oxidation of CO on Pd-doped boron nitride nanotube (BNNT). The electronic structures and thermodynamic parameters of CO and O-2, which are adsorbed on BNNT substrate with Pd embedded at the N- and B- vacancy, are examined in detail. It is revealed that the BNNT substrate with vacancy strongly stabilizes the Pd adatom. Benefit from the B vacancy defect, the Pd atom binds strongly with BNNT. The interaction energy of 3.74 eV is strong enough to prevent the aggregation of Pd atom. With B vacancy, Pd atom accepts extra electron from the substrate, causing O-2 to bind stronger than CO molecule. An additional charge is transferred to O-2 when CO and O-2 are co-adsorbed on the substrate. This additional charge thus strengthens the O-2 and CO adsorption and changes the electronic structure properties of the tube. Four proposed CO oxidation mechanisms (Eley-Rideal (ER), Langmuir-Hinshelwood (LH), termolecular Eley-Rideal (TER), and termolecular Langmuir-Hinshelwood (TLH)) are studied by calculating the reaction energy barriers along the minimum-energy pathway. It is found that a large reaction barrier exists in the rate-limiting step of the ER mechanism. It is then suggested that the most probable mechanisms for CO oxidation on Pd doped boron vacancy BNNT (Pd-Bv/BNNT) could be the LH mechanism and the new TER and TLH mechanisms under experimental circumstances. (C) 2017 Published by Elsevier B.V.