Reaction mechanism of ethylene glycol decomposition on Pt model catalysts: A density functional theory study

Understanding and controlling bond beak sequence is important in catalytic processes. The DFT-GGA method combined with slab model was performed to study the ethylene glycol decomposition on various Pt model catalysts such as close-packed Pt(111), stepped Pt(211) and a more open one, Pt(100). Calculation results show that the adsorption energies of ethylene glycol and other decomposition species depend on the coordination number of surface atom, that is, low coordination number correspond to high adsorption energy. Moreover, it was found that final products of ethylene glycol decomposition are CO and H-2 on all model catalysts, but the reaction mechanism varies: On Pt(111), the first step is O-H bond scission, followed by C-H bond cleavage, namely C2H6O2 -> HOCH2CH2O + H -> HOCH2CHO + 2H -> HOCH2CO +3H -> OCH2CO + 4H -> OCHCO + 5H -> CO + HCO + 5H -> 2CO + 6H -> 2CO + 3H(2); On Pt(211) and Pt(100), however, it is a second O-H bond cleavage that follows the initial O-H bond scission, that is, C2H6O2 -> HOCH2CH2O+H -> OCH2CH2O + 2H -> OCHCH2O +3H -> OCHCHO -> 2HCO + 4H -> 2CO + 6H -> 2CO + 3H(2) on Pt(211), and C2H6O2 -> HOCH2CH2O + 4H -> OCH2CH2O +2H -> OCHCH2O+3H -> OCCH2O+4H -> CO+H2CO+4H -> CO+HCO+5H -> 2CO+6H -> 2CO+3H(2) on Pt(100) For the catalytic order of ethylene glycol to form H-2, it may be determined based on the rate-controlling step, and it is Pt(111)>Pt(211)>Pt(100). (C) 2016 Elsevier B.V. All rights reserved.