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Surface reactivity enhancement on a Pd/Bi2Te3 heterostructure through robust topological surface states.

He QL, Lai YH, Lu Y, Law KT, Sou IK - Sci Rep (2013)

Bottom Line: We present a study of the surface reactivity of a Pd/Bi2Te3 thin film heterostructure.The topological surface states from Bi2Te3, being delocalized and robust owing to their topological natures, were found to act as an effective electron bath that significantly enhances the surface reactivity of palladium in the presence of two oxidizing agents, oxygen and tellurium respectively, which is consistent with a theoretical calculation.A partially inserted iron ferromagnetic layer at the interface of this heterostructure was found to play two competing roles arising from the higher-lying d-band center of the Pd/Fe bilayer and the interaction between the ferromagnetism and the surface spin texture of Bi2Te3 on the surface reactivity and their characteristics also demonstrate that the electron bath effect is long-lasting against accumulated thickness of adsorbates.

View Article: PubMed Central - PubMed

Affiliation: William Mong Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, Hong Kong, SAR China.

ABSTRACT
We present a study of the surface reactivity of a Pd/Bi2Te3 thin film heterostructure. The topological surface states from Bi2Te3, being delocalized and robust owing to their topological natures, were found to act as an effective electron bath that significantly enhances the surface reactivity of palladium in the presence of two oxidizing agents, oxygen and tellurium respectively, which is consistent with a theoretical calculation. The surface reactivity of the adsorbed tellurium on this heterostructure is also intensified possibly benefitted from the effective transfer of the bath electrons. A partially inserted iron ferromagnetic layer at the interface of this heterostructure was found to play two competing roles arising from the higher-lying d-band center of the Pd/Fe bilayer and the interaction between the ferromagnetism and the surface spin texture of Bi2Te3 on the surface reactivity and their characteristics also demonstrate that the electron bath effect is long-lasting against accumulated thickness of adsorbates.

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Schematic illustrations of the energy band structures and the temporal evolvements of the oxidation of Te of S#4 under the impacts of a higher-lying d-band center [for the region W/Fe (left)] and the TSSs [for the region W/O Fe (right)].(a) The interaction between the adsorbates and the d electrons on the surface of Pd causes an upswing of the energy of the d-band center, Ed, leading to split-off bonding and antibonding states in the energy spectrum22. The upshifted antibonding states above the Fermi level EF become mostly empty, which enhances the surface adsorption. The upward shift of the TSSs in the region W/O Fe indicates that the surface electrons are transferred out of the TSSs, which promotes the Ten clusters and O2 molecules toward dissociative adsorption on Pd12. (b) The temporal evolutions of the oxidation of Te in the region W/Fe and W/O Fe under the effect of a higher-lying d-band center of Pd/Fe and the TSSs respectively. The arrows shown in this diagram represent the high-lying d-band effect (blue) and the extending of the surface electrons (red).
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f5: Schematic illustrations of the energy band structures and the temporal evolvements of the oxidation of Te of S#4 under the impacts of a higher-lying d-band center [for the region W/Fe (left)] and the TSSs [for the region W/O Fe (right)].(a) The interaction between the adsorbates and the d electrons on the surface of Pd causes an upswing of the energy of the d-band center, Ed, leading to split-off bonding and antibonding states in the energy spectrum22. The upshifted antibonding states above the Fermi level EF become mostly empty, which enhances the surface adsorption. The upward shift of the TSSs in the region W/O Fe indicates that the surface electrons are transferred out of the TSSs, which promotes the Ten clusters and O2 molecules toward dissociative adsorption on Pd12. (b) The temporal evolutions of the oxidation of Te in the region W/Fe and W/O Fe under the effect of a higher-lying d-band center of Pd/Fe and the TSSs respectively. The arrows shown in this diagram represent the high-lying d-band effect (blue) and the extending of the surface electrons (red).

Mentions: The experimental results obtained on S#4 as described in the last two paragraphs provide the evidence that though the role of a higher-lying d-band center of Pd/Fe win against the electron bath effect from the BT thin film at an initial stage of the enhancement of the surface reactivity, the latter will take over the former at a later stage. This observation in fact can be explained by our previous prediction that the accumulation of Te-oxide will gradually diminish the role of the higher-lying d-band center, while the role of the electron bath effect originated from the TI persists assuming the electrons of TSSs can partially tunnel onto the surface of Te-oxide layer. The long-lasting enhancement of the surface reactivity attributed to the facilitation through the electron bath of TSSs may find novel important applications in surface science, gas sensing and catalysis. Fig. 5 illustrates the energy band structures and the temporal evolvements of the oxidation of Te of S#4 under the impacts of a higher-lying d-band center and the TSSs, which are based on the experimental results obtained in this work.


Surface reactivity enhancement on a Pd/Bi2Te3 heterostructure through robust topological surface states.

He QL, Lai YH, Lu Y, Law KT, Sou IK - Sci Rep (2013)

Schematic illustrations of the energy band structures and the temporal evolvements of the oxidation of Te of S#4 under the impacts of a higher-lying d-band center [for the region W/Fe (left)] and the TSSs [for the region W/O Fe (right)].(a) The interaction between the adsorbates and the d electrons on the surface of Pd causes an upswing of the energy of the d-band center, Ed, leading to split-off bonding and antibonding states in the energy spectrum22. The upshifted antibonding states above the Fermi level EF become mostly empty, which enhances the surface adsorption. The upward shift of the TSSs in the region W/O Fe indicates that the surface electrons are transferred out of the TSSs, which promotes the Ten clusters and O2 molecules toward dissociative adsorption on Pd12. (b) The temporal evolutions of the oxidation of Te in the region W/Fe and W/O Fe under the effect of a higher-lying d-band center of Pd/Fe and the TSSs respectively. The arrows shown in this diagram represent the high-lying d-band effect (blue) and the extending of the surface electrons (red).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750537&req=5

f5: Schematic illustrations of the energy band structures and the temporal evolvements of the oxidation of Te of S#4 under the impacts of a higher-lying d-band center [for the region W/Fe (left)] and the TSSs [for the region W/O Fe (right)].(a) The interaction between the adsorbates and the d electrons on the surface of Pd causes an upswing of the energy of the d-band center, Ed, leading to split-off bonding and antibonding states in the energy spectrum22. The upshifted antibonding states above the Fermi level EF become mostly empty, which enhances the surface adsorption. The upward shift of the TSSs in the region W/O Fe indicates that the surface electrons are transferred out of the TSSs, which promotes the Ten clusters and O2 molecules toward dissociative adsorption on Pd12. (b) The temporal evolutions of the oxidation of Te in the region W/Fe and W/O Fe under the effect of a higher-lying d-band center of Pd/Fe and the TSSs respectively. The arrows shown in this diagram represent the high-lying d-band effect (blue) and the extending of the surface electrons (red).
Mentions: The experimental results obtained on S#4 as described in the last two paragraphs provide the evidence that though the role of a higher-lying d-band center of Pd/Fe win against the electron bath effect from the BT thin film at an initial stage of the enhancement of the surface reactivity, the latter will take over the former at a later stage. This observation in fact can be explained by our previous prediction that the accumulation of Te-oxide will gradually diminish the role of the higher-lying d-band center, while the role of the electron bath effect originated from the TI persists assuming the electrons of TSSs can partially tunnel onto the surface of Te-oxide layer. The long-lasting enhancement of the surface reactivity attributed to the facilitation through the electron bath of TSSs may find novel important applications in surface science, gas sensing and catalysis. Fig. 5 illustrates the energy band structures and the temporal evolvements of the oxidation of Te of S#4 under the impacts of a higher-lying d-band center and the TSSs, which are based on the experimental results obtained in this work.

Bottom Line: We present a study of the surface reactivity of a Pd/Bi2Te3 thin film heterostructure.The topological surface states from Bi2Te3, being delocalized and robust owing to their topological natures, were found to act as an effective electron bath that significantly enhances the surface reactivity of palladium in the presence of two oxidizing agents, oxygen and tellurium respectively, which is consistent with a theoretical calculation.A partially inserted iron ferromagnetic layer at the interface of this heterostructure was found to play two competing roles arising from the higher-lying d-band center of the Pd/Fe bilayer and the interaction between the ferromagnetism and the surface spin texture of Bi2Te3 on the surface reactivity and their characteristics also demonstrate that the electron bath effect is long-lasting against accumulated thickness of adsorbates.

View Article: PubMed Central - PubMed

Affiliation: William Mong Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, Hong Kong, SAR China.

ABSTRACT
We present a study of the surface reactivity of a Pd/Bi2Te3 thin film heterostructure. The topological surface states from Bi2Te3, being delocalized and robust owing to their topological natures, were found to act as an effective electron bath that significantly enhances the surface reactivity of palladium in the presence of two oxidizing agents, oxygen and tellurium respectively, which is consistent with a theoretical calculation. The surface reactivity of the adsorbed tellurium on this heterostructure is also intensified possibly benefitted from the effective transfer of the bath electrons. A partially inserted iron ferromagnetic layer at the interface of this heterostructure was found to play two competing roles arising from the higher-lying d-band center of the Pd/Fe bilayer and the interaction between the ferromagnetism and the surface spin texture of Bi2Te3 on the surface reactivity and their characteristics also demonstrate that the electron bath effect is long-lasting against accumulated thickness of adsorbates.

Show MeSH