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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) O2 (O in red) adsorbed on graphene supported on Zn doped Fe/Ni (111). The adsorption energy of O2 is around 0.42 eV. The isosurface of charge redistribution caused by O2 adsorption is superimposed. (b,c) are side views of charge redistribution. (d) projected density of states (PDOS) of O2 molecule before (upper) and after (lower) adsorption. The PDOS of O2 before adsorption is calculated by putting the molecule 5 Å away from the graphene in the same supercell.
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f3: (a) O2 (O in red) adsorbed on graphene supported on Zn doped Fe/Ni (111). The adsorption energy of O2 is around 0.42 eV. The isosurface of charge redistribution caused by O2 adsorption is superimposed. (b,c) are side views of charge redistribution. (d) projected density of states (PDOS) of O2 molecule before (upper) and after (lower) adsorption. The PDOS of O2 before adsorption is calculated by putting the molecule 5 Å away from the graphene in the same supercell.

Mentions: We show in Fig. 3a the most stable adsorption configuration of O2 on graphene that is supported on Zn doped Fe/Ni (111). The adsorption energy of O2 in this case is calculated to be around 0.42 eV. The O-O bond of the O2 molecule is significantly elongated to 1.48 Å (compared with 1.24 Å in gas phase). We also tested other inequivalent adsorption sites near the Zn impurity (Figure S1 in the supporting information), and found that the site shown in Fig. 3a is the only one that shows chemisorption of O2. When far away from the impurity atom, there is no binding of O2. Note that CO still does not bind to graphene after doping. We also considered cases of doping multiple Zn atoms in the supercell and found that when two Zn impurities are close to each other, only one O2 is adsorbed on graphene (see Figure S2 in the supporting information). The adsorption energy O2 is calculated from equation, , where is the energy of the supported graphene and an O2 that is 5 Å away from graphene surface.


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

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

(a) O2 (O in red) adsorbed on graphene supported on Zn doped Fe/Ni (111). The adsorption energy of O2 is around 0.42 eV. The isosurface of charge redistribution caused by O2 adsorption is superimposed. (b,c) are side views of charge redistribution. (d) projected density of states (PDOS) of O2 molecule before (upper) and after (lower) adsorption. The PDOS of O2 before adsorption is calculated by putting the molecule 5 Å away from the graphene in the same supercell.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: (a) O2 (O in red) adsorbed on graphene supported on Zn doped Fe/Ni (111). The adsorption energy of O2 is around 0.42 eV. The isosurface of charge redistribution caused by O2 adsorption is superimposed. (b,c) are side views of charge redistribution. (d) projected density of states (PDOS) of O2 molecule before (upper) and after (lower) adsorption. The PDOS of O2 before adsorption is calculated by putting the molecule 5 Å away from the graphene in the same supercell.
Mentions: We show in Fig. 3a the most stable adsorption configuration of O2 on graphene that is supported on Zn doped Fe/Ni (111). The adsorption energy of O2 in this case is calculated to be around 0.42 eV. The O-O bond of the O2 molecule is significantly elongated to 1.48 Å (compared with 1.24 Å in gas phase). We also tested other inequivalent adsorption sites near the Zn impurity (Figure S1 in the supporting information), and found that the site shown in Fig. 3a is the only one that shows chemisorption of O2. When far away from the impurity atom, there is no binding of O2. Note that CO still does not bind to graphene after doping. We also considered cases of doping multiple Zn atoms in the supercell and found that when two Zn impurities are close to each other, only one O2 is adsorbed on graphene (see Figure S2 in the supporting information). The adsorption energy O2 is calculated from equation, , where is the energy of the supported graphene and an O2 that is 5 Å away from graphene surface.

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.