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Greatly Enhancing Catalytic Activity of Graphene by Doping the Underlying Metal Substrate.

Guo N, Xi Y, Liu S, Zhang C - Sci Rep (2015)

Bottom Line: When a Zn atom is doped into the substrate, the catalytic activity of the supported graphene is greatly enhanced, and the reaction barrier of the catalyzed CO oxidation is reduced to less than 0.5 eV.Intriguing reaction mechanism of catalyzed CO oxidation is revealed.These studies suggest a new class of graphene-based catalysts and pave the way for future applications of graphene in solid-state catalysis.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Graphene Research Centre, National University of Singapore, Singapore 117542.

ABSTRACT
Graphene-based solid-state catalysis represents a new direction in applications of graphene and has attracted a lot of interests recently. However, the difficulty in fine control and large-scale production of previously proposed graphene catalysts greatly limits their industrial applications. Here we present a novel way to enhance the catalytic activity of graphene, which is highly efficient yet easy to fabricate and control. By first-principles calculations, we show that when the underlying metal substrate is doped with impurities, the catalytic activity of the supported graphene can be drastically enhanced. Graphene supported on a Fe/Ni(111) surface is chosen as a model catalyst, and the chemical reaction of CO oxidation is used to probe the catalytic activity of graphene. When the underlying Fe/Ni(111) substrate is impurity free, the graphene is catalytically inactive. When a Zn atom is doped into the substrate, the catalytic activity of the supported graphene is greatly enhanced, and the reaction barrier of the catalyzed CO oxidation is reduced to less than 0.5 eV. Intriguing reaction mechanism of catalyzed CO oxidation is revealed. These studies suggest a new class of graphene-based catalysts and pave the way for future applications of graphene in solid-state catalysis.

No MeSH data available.


(a) Atomic model of graphene supported on Fe/Ni (111) (Ni in dark red, Fe in grey, C in black). Five layers of Ni are included in the model. The supercell includes 4 × 4 of pristine unit cell of graphene and 15 Å of vacuum in the direction perpendicular to the graphene surface; (b,c) are the top and side views of the isosurface of charge redistribution caused by the adsorption of graphene. The isosurface value of 0.008 e/Å3. The accumulation (depletion) of electrons is denoted by yellow (green).
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f1: (a) Atomic model of graphene supported on Fe/Ni (111) (Ni in dark red, Fe in grey, C in black). Five layers of Ni are included in the model. The supercell includes 4 × 4 of pristine unit cell of graphene and 15 Å of vacuum in the direction perpendicular to the graphene surface; (b,c) are the top and side views of the isosurface of charge redistribution caused by the adsorption of graphene. The isosurface value of 0.008 e/Å3. The accumulation (depletion) of electrons is denoted by yellow (green).

Mentions: The atomic model of graphene on Fe/Ni (111) is shown in Fig. 1a where five layers of Ni are included in the supercell to make sure that the correct surface properties of Ni (111) can be obtained. In structure optimizations, three bottom layers of Ni are fixed to bulk structures. Our DFT calculations show that the Ni-Fe and graphene-Fe bond lengths are around 2.48 Å and 2.15 Å, respectively. The adsorption energy of graphene is estimated to be 0.42 eV per carbon pair. All of these results agree very well with previous studies21. In Fig. 1b,c, we plot the isosurface of charge redistribution caused by the graphene adsorption. The formation of chemical bonding between graphene and the top Fe layer can be clearly seen from the figures. Note that we also tested the effects of vdW interactions by the so-called DFT+D22 calculations. The DFT+D method gives unreasonably high adsorption energy of graphene (more than 1.27 eV per carbon pair). We therefore do not consider vdW interactions in the rest part of the paper.


Greatly Enhancing Catalytic Activity of Graphene by Doping the Underlying Metal Substrate.

Guo N, Xi Y, Liu S, Zhang C - Sci Rep (2015)

(a) Atomic model of graphene supported on Fe/Ni (111) (Ni in dark red, Fe in grey, C in black). Five layers of Ni are included in the model. The supercell includes 4 × 4 of pristine unit cell of graphene and 15 Å of vacuum in the direction perpendicular to the graphene surface; (b,c) are the top and side views of the isosurface of charge redistribution caused by the adsorption of graphene. The isosurface value of 0.008 e/Å3. The accumulation (depletion) of electrons is denoted by yellow (green).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4496776&req=5

f1: (a) Atomic model of graphene supported on Fe/Ni (111) (Ni in dark red, Fe in grey, C in black). Five layers of Ni are included in the model. The supercell includes 4 × 4 of pristine unit cell of graphene and 15 Å of vacuum in the direction perpendicular to the graphene surface; (b,c) are the top and side views of the isosurface of charge redistribution caused by the adsorption of graphene. The isosurface value of 0.008 e/Å3. The accumulation (depletion) of electrons is denoted by yellow (green).
Mentions: The atomic model of graphene on Fe/Ni (111) is shown in Fig. 1a where five layers of Ni are included in the supercell to make sure that the correct surface properties of Ni (111) can be obtained. In structure optimizations, three bottom layers of Ni are fixed to bulk structures. Our DFT calculations show that the Ni-Fe and graphene-Fe bond lengths are around 2.48 Å and 2.15 Å, respectively. The adsorption energy of graphene is estimated to be 0.42 eV per carbon pair. All of these results agree very well with previous studies21. In Fig. 1b,c, we plot the isosurface of charge redistribution caused by the graphene adsorption. The formation of chemical bonding between graphene and the top Fe layer can be clearly seen from the figures. Note that we also tested the effects of vdW interactions by the so-called DFT+D22 calculations. The DFT+D method gives unreasonably high adsorption energy of graphene (more than 1.27 eV per carbon pair). We therefore do not consider vdW interactions in the rest part of the paper.

Bottom Line: When a Zn atom is doped into the substrate, the catalytic activity of the supported graphene is greatly enhanced, and the reaction barrier of the catalyzed CO oxidation is reduced to less than 0.5 eV.Intriguing reaction mechanism of catalyzed CO oxidation is revealed.These studies suggest a new class of graphene-based catalysts and pave the way for future applications of graphene in solid-state catalysis.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Graphene Research Centre, National University of Singapore, Singapore 117542.

ABSTRACT
Graphene-based solid-state catalysis represents a new direction in applications of graphene and has attracted a lot of interests recently. However, the difficulty in fine control and large-scale production of previously proposed graphene catalysts greatly limits their industrial applications. Here we present a novel way to enhance the catalytic activity of graphene, which is highly efficient yet easy to fabricate and control. By first-principles calculations, we show that when the underlying metal substrate is doped with impurities, the catalytic activity of the supported graphene can be drastically enhanced. Graphene supported on a Fe/Ni(111) surface is chosen as a model catalyst, and the chemical reaction of CO oxidation is used to probe the catalytic activity of graphene. When the underlying Fe/Ni(111) substrate is impurity free, the graphene is catalytically inactive. When a Zn atom is doped into the substrate, the catalytic activity of the supported graphene is greatly enhanced, and the reaction barrier of the catalyzed CO oxidation is reduced to less than 0.5 eV. Intriguing reaction mechanism of catalyzed CO oxidation is revealed. These studies suggest a new class of graphene-based catalysts and pave the way for future applications of graphene in solid-state catalysis.

No MeSH data available.