DFT Investigation of High Temperature Water Gas Shift Reaction on Chromium-Iron Mixed Oxide Catalyst

摘要

As part of high temperature water gas shift reaction mechanism, CO and H_2O adsorptions on Fe_3O_4(111) and chromium atom substituted Fe_3O_4 (111) slab surfaces are investigated by means of periodic DFT approach using the Vienna Ab-initio Simulation Package (VASP). Fe_3O_4 bulk structure has been computed including the Hubbard (U) parameter to describe the on-site interaction of iron 3d electrons. Ooct1 is studied among the six Fe_3O_4 (111) terminations. Cr atom substitution on this surface is also examined. Cr atoms prefer to locate at top octahedral iron atom layer. Adsorption energies of CO on Ooct1 and Ooct2Cr are found as -96 kcal/mol and -47 kcal/mol. Water adsorption on Ooct1 surface is molecular with -54.88 kcal/mol adsorption energy. On the other hand, water adsorption on Ooct2Cr surface is dissociative with nearly same adsorption energy, -55.12 kcal/mol, indicating the catalytic effect of chromium atom.