DFT Study of Hydrogen-Assisted Dissociation of CO by HCO, COH, and HCOH Formation on Fe(100)

Abstract

DFT calculations using the GGA-PBE exchange correlation functional were used to investigate the effect of the hydrogen in the assisted CO dissociation on the Fe(100) surface. The formation mechanisms of the primary products CH, OH, CH2, and H2O involved in the Fischer-Tropsch synthesis have been studied. Three different routes were investigated passing through the HCO, COH, or HCOH intermediates. The energy barriers of the reactions were estimated using the nudged elastic band method (NEB). The energy profiles of assisted and double-assisted dissociations of CO are presented. The formation energies of HCO, COH, and HCOH intermediates are estimated to be endothermic with activation energies of 0.90, 1.07, and 2.13 eV, respectively. The formation of CH2 is energetically more favorable with the global reaction energy estimated to be -1.10 eV. The other CH, OH, and H2O intermediates have also endothermic formation energies with respect to the Fe(100)/(CO + H) system. The chemical bonding of the adsorbed intermediates and reactants was analyzed based on the population analysis, electron localization function, and pseudodifferential charge density. A comparison with direct CO dissociation leads to the conclusion that hydrogen-assisted processes constitute viable routes for CO dissociation on Fe (100) and alkanes formation.