A DFT+U study of acetylene selective hydrogenation on oxygen defective anatase (101) and rutile (110) TiO2 supported Pd4 cluster

Abstract

The reaction mechanisms for selective acetylene hydrogenation on three different supports, Pd(4) cluster, oxygen defective anatase (101), and rutile (110) titania supported Pd(4), cluster are studied using the density functional theory calculations with a Hubbard U correction (DFT+U). The present calculations show that the defect anatase support binds Pd(4) cluster more strongly than that of rutile titania due to the existence of Ti(3+) in anatase titania. Consequently, the binding energies of adsorbed species such as acetylene and ethylene on Pd(4) cluster become weaker on anatase supported catalysts compared to the rutile supported Pd(4) cluster. Anatase catalyst has higher selectivity of acetylene hydrogenation than rutile catalyst. On the one hand, the activation energies of ethylene formation are similar on the two catalysts, while they vary a lot on ethyl formation. The rutile supported Pd catalyst with lower activation energy is preferable for further hydrogenation. On the other hand, the relatively weak adsorption energy of ethylene is gained on anatase surface, which means it is easier for ethylene desorption, hence getting higher selectivity. For further understanding, the energy decomposition method and micro-kinetic analysis are also introduced.

Density functional theory study of ethylene adsorption on clean anatase TiO2 (001) surface

“…Aside from the numerous studies that have been done onethylene adsorption on metal andtransition metal surfaces [6,[12][13][14][15][16][17][18], ethylene adsorption on metal oxide surface is a topic that also received quite significant amount of attention [9,[19][20][21][22]. In particular for ethylene interaction with TiO 2 , several studies -in which most of them are experimental works -have been carried out [7,9,19,20,[23][24][25].…”

First-principles kinetic modeling in heterogeneous catalysis: an industrial perspective on best-practice, gaps and needs

“…Models that gradually start to integrate support effects rely typically either on fully periodic film formulations, in which several layers of the active phase are deposited on a periodically modeled support, 24 or on approaches in which finite clusters are deposited on a periodically modeled support. [25][26][27][28][29] The first approach is most interesting from a computational point of view, as it only requires relatively small unit cells. On the other hand, results obtained in this way may be severely affected by the (spurious) strain that is imposed by the lattice mismatch between the active phase and the support, or by a falsified charge transfer due to electrostatic effects between the periodic image cells.…”

Ultra-stable metal nano-catalyst synthesis strategy: a perspective

“…In addition, Wang et al [67] systematically studied the crystal plane effect on the stability of NPs using anatase (101) and rutile (110) TiO 2 by density functional theory (DFT) calculation. They found that the absorption energies of the Pd 4 cluster on defective anatase (101) and rutile (110) TiO 2 showed an obvious difference (-4.53 and -3.19 eV, respectively), which indicates a stronger interaction between Pd 4 cluster and anatase (101) TiO 2 compared to that of the rutile (110) TiO 2 .…”