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Catalytic activities of noble metal atoms on WO3 (001): nitric oxide adsorption.

Ren X, Zhang S, Li C, Li S, Jia Y, Cho JH - Nanoscale Res Lett (2015)

Bottom Line: This relatively stronger bonding of NO to the W atom is found to be associated with the larger charge transfer of 0.43 e (Cu) and 0.33 e (Ag) from the surface to adsorbed NO.On such an Au-WO3(001) complex, the NO molecule is found to form a bond to the Au atom with E ads = -1.32 eV.Because of a large electronegativity of Au atom, the adsorbed NO molecule captures the less electrons (0.04 e) from the surface compared to the Cu and Ag catalysts.

View Article: PubMed Central - PubMed

Affiliation: International Laboratory for Quantum Functional Materials of Henan, and School of Physics and Engineering, Zhengzhou University, Zhengzhou, 450001 China ; School of Mechanical and Electrical Engineering, Henan Institute of Science and Technology, Xinxiang, 453003 China.

ABSTRACT
Using first-principles density functional theory calculations within the generalized gradient approximation, we investigate the adsorption of NO molecule on a clean WO3(001) surface as well as on the noble metal atom (Cu, Ag, and Au)-deposited WO3(001) surfaces. We find that on a clean WO3 (001) surface, the NO molecule binds to the W atom with an adsorption energy (E ads) of -0.48 eV. On the Cu- and Ag-deposited WO3(001) surface where such noble metal atoms prefer to adsorb on the hollow site, the NO molecule also binds to the W atom with E ads = -1.69 and -1.41 eV, respectively. This relatively stronger bonding of NO to the W atom is found to be associated with the larger charge transfer of 0.43 e (Cu) and 0.33 e (Ag) from the surface to adsorbed NO. However, unlike the cases of Cu-WO3(001) and Ag-WO3(001), Au atoms prefer to adsorb on the top of W atom. On such an Au-WO3(001) complex, the NO molecule is found to form a bond to the Au atom with E ads = -1.32 eV. Because of a large electronegativity of Au atom, the adsorbed NO molecule captures the less electrons (0.04 e) from the surface compared to the Cu and Ag catalysts. Our findings not only provide useful information about the NO adsorption on a clean WO3(001) surface as well as on the noble metal atoms deposited WO3(001) surfaces but also shed light on a higher sensitive WO3 sensor for NO detection employing noble metal catalysts.

No MeSH data available.


Charge density difference for the most stable configurations of NO adsorption. NO molecule adsorbed on the (a) clean, (b) Cu-deposited, (c) Ag-deposited, and (d) Au-deposited WO3 (001) surfaces. The gain and loss of electrons are drawn in bright and dark colors with an isosurface of 0.005 e/Å3, respectively.
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Fig3: Charge density difference for the most stable configurations of NO adsorption. NO molecule adsorbed on the (a) clean, (b) Cu-deposited, (c) Ag-deposited, and (d) Au-deposited WO3 (001) surfaces. The gain and loss of electrons are drawn in bright and dark colors with an isosurface of 0.005 e/Å3, respectively.

Mentions: To evaluate charge transfer in the S1 configuration, we perform Bader charge analysis for NO before and after its adsorption on the WO3(001) surface [37,38]. The results for a free NO molecule and adsorbed NO on various substrates are given in Table 1. We find that, upon NO adsorption on a clean WO3(001) surface, the electrons in the N (O) atom increase (decrease) from 4.44 (6.56) to 4.84 (6.35) e, giving rise to an increase of 0.19 e in adsorbed NO molecule. This fact shows that adsorbed NO molecule captures electrons from the WO3(001) surface, indicating that NO behaves as a charge accepter. Indeed, the charge density difference, defined as ∆ρ = ρNO/WO3 − (ρNO + ρWO3), clearly shows a charge transfer from the O (in NO molecule) and W atoms to the N atom; see Figure 3a. As a consequence of the additional electrons in NO in the NO/WO3(001) system, the bond length dN-O of NO molecule slightly increases to 1.181 Å, compared to that (1.170 Å) of a free NO molecule; see Table 1.Table 1


Catalytic activities of noble metal atoms on WO3 (001): nitric oxide adsorption.

Ren X, Zhang S, Li C, Li S, Jia Y, Cho JH - Nanoscale Res Lett (2015)

Charge density difference for the most stable configurations of NO adsorption. NO molecule adsorbed on the (a) clean, (b) Cu-deposited, (c) Ag-deposited, and (d) Au-deposited WO3 (001) surfaces. The gain and loss of electrons are drawn in bright and dark colors with an isosurface of 0.005 e/Å3, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385050&req=5

Fig3: Charge density difference for the most stable configurations of NO adsorption. NO molecule adsorbed on the (a) clean, (b) Cu-deposited, (c) Ag-deposited, and (d) Au-deposited WO3 (001) surfaces. The gain and loss of electrons are drawn in bright and dark colors with an isosurface of 0.005 e/Å3, respectively.
Mentions: To evaluate charge transfer in the S1 configuration, we perform Bader charge analysis for NO before and after its adsorption on the WO3(001) surface [37,38]. The results for a free NO molecule and adsorbed NO on various substrates are given in Table 1. We find that, upon NO adsorption on a clean WO3(001) surface, the electrons in the N (O) atom increase (decrease) from 4.44 (6.56) to 4.84 (6.35) e, giving rise to an increase of 0.19 e in adsorbed NO molecule. This fact shows that adsorbed NO molecule captures electrons from the WO3(001) surface, indicating that NO behaves as a charge accepter. Indeed, the charge density difference, defined as ∆ρ = ρNO/WO3 − (ρNO + ρWO3), clearly shows a charge transfer from the O (in NO molecule) and W atoms to the N atom; see Figure 3a. As a consequence of the additional electrons in NO in the NO/WO3(001) system, the bond length dN-O of NO molecule slightly increases to 1.181 Å, compared to that (1.170 Å) of a free NO molecule; see Table 1.Table 1

Bottom Line: This relatively stronger bonding of NO to the W atom is found to be associated with the larger charge transfer of 0.43 e (Cu) and 0.33 e (Ag) from the surface to adsorbed NO.On such an Au-WO3(001) complex, the NO molecule is found to form a bond to the Au atom with E ads = -1.32 eV.Because of a large electronegativity of Au atom, the adsorbed NO molecule captures the less electrons (0.04 e) from the surface compared to the Cu and Ag catalysts.

View Article: PubMed Central - PubMed

Affiliation: International Laboratory for Quantum Functional Materials of Henan, and School of Physics and Engineering, Zhengzhou University, Zhengzhou, 450001 China ; School of Mechanical and Electrical Engineering, Henan Institute of Science and Technology, Xinxiang, 453003 China.

ABSTRACT
Using first-principles density functional theory calculations within the generalized gradient approximation, we investigate the adsorption of NO molecule on a clean WO3(001) surface as well as on the noble metal atom (Cu, Ag, and Au)-deposited WO3(001) surfaces. We find that on a clean WO3 (001) surface, the NO molecule binds to the W atom with an adsorption energy (E ads) of -0.48 eV. On the Cu- and Ag-deposited WO3(001) surface where such noble metal atoms prefer to adsorb on the hollow site, the NO molecule also binds to the W atom with E ads = -1.69 and -1.41 eV, respectively. This relatively stronger bonding of NO to the W atom is found to be associated with the larger charge transfer of 0.43 e (Cu) and 0.33 e (Ag) from the surface to adsorbed NO. However, unlike the cases of Cu-WO3(001) and Ag-WO3(001), Au atoms prefer to adsorb on the top of W atom. On such an Au-WO3(001) complex, the NO molecule is found to form a bond to the Au atom with E ads = -1.32 eV. Because of a large electronegativity of Au atom, the adsorbed NO molecule captures the less electrons (0.04 e) from the surface compared to the Cu and Ag catalysts. Our findings not only provide useful information about the NO adsorption on a clean WO3(001) surface as well as on the noble metal atoms deposited WO3(001) surfaces but also shed light on a higher sensitive WO3 sensor for NO detection employing noble metal catalysts.

No MeSH data available.