Computational understanding of Fe-Pt synergy in promoting guaiacol hydrodeoxygenation

Abstract

The synergistic action of Fe-Pt bimetallic catalyst for the hydrodeoxygenation (HDO) of guaiacol was studied by density functional theory calculations, with a focus on exploring the effect of size of supported Pt clusters on Fe(211). Energetically favorable adsorption configurations of guaiacol on stable Pt4/Fe(211) and Pt10/Fe(211) surface models were identified, and the adsorption strength enhanced with increasing the Pt cluster size which was caused by different charge transfer between the guaiacol molecule and catalyst surface. Three possible paths of C-O bonds cleavage for guaiacol HDO to different aromatic compounds were examined involving demethoxylation, dehydroxylation and demethylation. On both the Pt4/Fe(211) and Pt10/Fe(211) surfaces, phenol formation from direct CAr–OCH3 cleavage was kinetically most favorable whereas the direct CArO-CH3 cleavage to form catechol was hindered due to large barriers. The electronic property analysis including Crystal Orbital Hamiltonian Population (COHP) and Bader charge explained the intrinsic differences in reaction performance on the two Fe-Pt surfaces. Different size of Pt clusters causes dissimilar changes in the electronic properties of Fe catalyst surface, thereby affecting the adsorption and reaction property. Small supported Ptn clusters is conducive to the selective deoxygenation of guaiacol. The stabilization of Fe step surface as well as the facilitation of surface H* species formation and CAr-O bond activation by the introduction of Pt cluster are expected to significantly contribute to the Fe-Pt synergy in HDO catalysis.