Greatly enhanced adsorption and catalytic activity of Au and Pt clusters on defective graphene.

Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore.
The Journal of Chemical Physics (Impact Factor: 3.12). 05/2010; 132(19):194704. DOI: 10.1063/1.3427246
Source: PubMed

ABSTRACT We report an investigation on CO oxidation catalyzed by Au(8) or Pt(4) clusters on defective graphene using first-principles approach based on density functional theory. The simplest single-carbon-vacancy defect on graphene was found to play an essential role in the catalyzed chemical reaction of CO oxidation. When supported on a defect-free graphene sheet, the reaction barrier of CO oxidation catalyzed by Au(8) (Pt(4)) clusters was estimated to be around 3.0 eV (0.5 eV), and when adsorbed on defective graphene, the reaction barrier was greatly reduced to around 0.2 eV (0.13 eV).

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    ABSTRACT: Theoretical studies on the structure, stability, and magnetic properties of icosahedral TM13 (TM = Fe, Co, Ni) clusters, deposited on pristine (defect free) and defective graphene sheet as well as graphene flakes, have been carried out within a gradient corrected density functional framework. The defects considered in our study include a carbon vacancy for the graphene sheet and a five-membered and a seven-membered ring structures for graphene flakes (finite graphene chunks). It is observed that the presence of defect in the substrate has a profound influence on the electronic structure and magnetic properties of graphene-transition metal complexes, thereby increasing the binding strength of the TM cluster on to the graphene substrate. Among TM13 clusters, Co13 is absorbed relatively more strongly on pristine and defective graphene as compared to Fe13 and Ni13 clusters. The adsorbed clusters show reduced magnetic moment compared to the free clusters.
    The Journal of Chemical Physics 08/2014; 141(7):074707. · 3.12 Impact Factor
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    ABSTRACT: We demonstrate efficient physical functionalization of single layer graphene with Au nanoparticles mediated by in-plane defects in graphene grown by a chemical vapor deposition technique. The effect of ultra thin Au layer on the single layer, bi layer and few layer graphene with intrinsic defects was studied by resonance Raman spectroscopy and high resolution transmission electron microscopy (HRTEM). We observed a striking enhancement in the intensity of sharp D and D' bands after sputter deposition of ultra thin Au layer on graphene. In contrast, G and 2D bands shows lower enhancement in intensity and change in line width due to the charge transfer from Au to the graphene and strong interaction between the Au and graphene layers, respectively. X-ray photo electron spectroscopy (XPS) analysis shows 40% decrease in integrated intensity ratio of sp3 and sp2 bands in C−1s spectra after Au functionalization indicating bonding of Au atoms preferentially at the defect sites in graphene. This was further substantiated by HRTEM imaging and position dependent Raman spectral line shape analysis. The calculations of inter defect distance and areal defect density from the Raman analysis on the graphene-Au hybrid are in close agreement with the HRTEM analysis. Further, Raman spectral line shape dependence of Au functionalization on the number of layers in graphene reveals that Au functionalised single layer graphene behaves like a pristine bilayer graphene due to strong interaction between Au and graphene layer. These results open up possibilities for efficient physical functionalization of graphene with foreign atoms through defect engineering for novel applications of graphene in catalysis, biosensors, optoelectronic and photonic devices.
    The Journal of Physical Chemistry C 06/2014; · 4.84 Impact Factor
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    ABSTRACT: The stability of doped graphene sheets and a catalytic platinum (Pt) film on the doped sheets was investigated for a variety of dopants, using the first-principles calculations in the density functional theory. It was shown that the doping (dopant-substitution) energy increases as the differences of atomic radius and valency increase between the dopant atom and the host carbon atom. On the other hand, the adsorption energy of the Pt film becomes larger on doped graphene sheets, compared to that on undoped graphene sheet. We found a strong correlation between the adsorption and doping energies: the adsorption energy increases as the doping energy increases. This correlation occurs because the Pt-film adsorption partially releases hetero-valency-induced doping-energy loss through electron redistribution and atom-position change. We showed that cation–anion dopant pairs in the graphene sheet are also effective to stabilize adsorbed Pt films.
    Surface Science. 01/2014; 621:7–15.

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