A comparative theoretical study for the methanol dehydrogenation to CO over Pt3 and PtAu2 clusters

Abstract

The density functional theory (DFT) calculations are carried out to study the mechanism details and the ensemble effect of methanol dehydrogenation over Pt(3) and PtAu(2) clusters, which present the smallest models of pure Pt clusters and bimetallic PtAu clusters. The energy diagrams are drawn out along both the initial O-H and C-H bond scission pathways via the four sequential dehydrogenation processes, respectively, i.e., CH(3)OH → CH(2)OH → CH(2)O → CHO → CO and CH(3)OH → CH(3)O → CH(2)O → CHO → CO, respectively. It is revealed that the reaction kinetics over PtAu(2) is significantly different from that over Pt(3). For the Pt(3)-mediated reaction, the C-H bond scission pathway, where an ensemble composed of two Pt atoms is required to complete methanol dehydrogenation, is energetically more favorable than the O-H bond scission pathway, and the maximum barrier along this pathway is calculated to be 12.99 kcal mol(-1). In contrast, PtAu(2) cluster facilitates the reaction starting from the O-H bond scission, where the Pt atom acts as the active center throughout each elementary step of methanol dehydrogenation, and the initial O-H bond scission with a barrier of 21.42 kcal mol(-1) is the bottom-neck step of methanol decomposition. Importantly, it is shown that the complete dehydrogenation product of methanol, CO, can more easily dissociate from PtAu(2) cluster than from Pt(3) cluster. The calculated results over the model clusters provide assistance to some extent for understanding the improved catalytic activity of bimetal PtAu catalysts toward methanol oxidation in comparison with pure Pt catalysts.

Platinum catalyzed hydrodeoxygenation of guaiacol in illumination of cresol production: a density functional theory study

“…Furthermore, recent works [ 29 , 30 ] based on such small catalyst clusters have proved their catalytic performances compared to their experimental or theoretical counterparts, but these works were carried out for different components. Therefore, the reliability of the Pt 3 catalyst model for the present kind of study may require its testing by experimental kinetic analysis of HDO of guaiacol which accompanies the productions of cresols along with other hydrodeoxygenated products.…”

“…The Pt 3 catalyst cluster [ 30 ] has been checked for its ground state configuration by running wave function stability analysis and the ground state laid in singlet spin state. Similarly, the complex of Pt 3 and guaiacol has been checked for its ground state and it also laid in the singlet state.…”

Bamboo shaped carbon nanotube supported platinum electrocatalyst synthesized by high power ultrasonic-assisted impregnation method for methanol electrooxidation and related density functional theory calculations

“…Similar to previous studies, a dehydrogenation mechanism where H atoms were removed in step from the methanol molecule was studied [49,50]. The adsorption of different possible intermediates (CH 3 OH, CH 2 OH, CHOH, COH, CO, H) on different CNTs was considered in order to calculate the reaction energies for the methanol decomposition reaction.…”

The catalytic activity of PtnCum (n+m=3, m≠3) clusters for methanol dehydrogenation to CO

“…To develop DMFCs and provide comprehensive mechanistic insights, a large number of studies have been devoted to understand the methanol oxidation reaction processes on Pt electrodes. Two possible reaction paths for dehydrogenation of methanol to CO are proposed, one is methyl-adsorption (H-adsorption) initiated C-H bond cleavage [15][16][17], and the other is oxygen-adsorption (O-adsorption) initiated O-H bond cleavage [17][18][19][20][21][22].…”