Density Functional Theory Studies of the Methanol Decomposition Reaction on Graphene-Supported Pt₁₃ Nanoclusters

Abstract

Defective graphene has been shown experimentally to be an excellent support for transition-metal electrocatalysts in direct methanol fuel cells. Prior computational modeling has revealed that the improved catalytic activity of graphene-supported metal clusters is in part due to increased resistance to catalyst sintering and to CO poisoning, but the increased reaction rate for the methanol decomposition reaction (MDR) is not yet fully explained. Using density functional theory, we investigate the adsorption and reaction thermodynamics of MDR intermediates on defective graphene-supported Pt13 nanoclusters with realistic, low-symmetry morphologies. We find that the support-induced shifts in catalyst electronic structure correlate well with an overall change in adsorption behavior of MDR intermediates and that the reaction thermodynamics are modified in a way that suggests the potential of greater catalytic activity. We also show that adsorption energy predictors established for traditional heterogeneous catalysis studies of MDR on macroscopic crystalline facets are equally valid on catalyst nanoclusters (supported or otherwise) with irregular, low-symmetry surface morphologies. Our studies provide theoretical insights into experimental observations of enhanced catalytic activity of graphene-supported Pt nanoclusters for MDR and suggest promising avenues for further tuning of catalytic activity through engineering of catalyst–support interactions.

A Theory/Experience Description of Support Effects in Carbon-Supported Catalysts

“…334 Alloying Pt with other TMs (Fe, Co, Ni, Cu and Pd) also reinforce this downshift. 336 Gasper et al 337 have found that the support-induced shifts in catalyst electronic structure correlates well with an overall change in adsorption behavior of methanol decomposition reaction intermediates, and that the reaction thermodynamics are modified in a way that suggests the potential of greater catalytic activity for Pt13 on graphene ML with SV. Interestingly, in the same work, it was shown that adsorption energy predictors [338][339][340] established for traditional heterogeneous catalysis studies of methanol decomposition reaction on macroscopic crystalline facets are equally valid on supported nanocatalysts with irregular surface morphologies, see Figure 13.…”

“…Interestingly, in the same work, it was shown that adsorption energy predictors [338][339][340] established for traditional heterogeneous catalysis studies of methanol decomposition reaction on macroscopic crystalline facets are equally valid on supported nanocatalysts with irregular surface morphologies, see Figure 13. 337 Copyright 2016 from the American Chemical Society.…”

Enhanced Catalysis of Pt 3 Clusters Supported on Graphene for N–H Bond Dissociation

“…40,41 In particular, graphene with carbon defects can provide anchor sites for supporting clusters and increase the stabilization of cluster bonding at the interface. 42,43 It is important to understand the interaction between the cluster and support so as to unravel the reaction mechanism and ultimately improve the catalytic performance.…”

Platinum single-atom adsorption on graphene: a density functional theory study

“…[10][11][12][13] Particularly interesting are Pt clusters supported by graphitic materials, such as carbon black, carbon nanotubes, and graphene, which have been extensively studied both experimentally, [14][15][16][17][18][19][20] and theoretically. [21][22][23][24][25][26][27][28][29][30][31][32][33][34] A better catalytic activity of small Pt clusters supported by graphene sheets has been demonstrated experimentally. 16,17 These results lead to the hypothesis that downsizing the Pt clusters to single atoms can enhance the catalytic activity.…”

“…36 The vacancies usually formed during the preparation are expected to have strong interactions with the Pt atoms as demonstrated in several theoretical studies. 23,31,32 Back et al have predicted the great potential of a single atom catalyst supported on defective graphene for CO 2 electroreduction applications. 37 However, the dispersion of the single Pt atoms on graphene is limited to the number of point defects.…”