Scanning Tunneling Microscopy Observation of Sulfur Electrodeposits on Graphite Single Crystals
The early stages of sulfur deposit growth on highly oriented pyrolytic graphite (HOPG) caused by HS- electrooxidation in a neutral buffered solution have been investigated using electrochemical techniques and ex situ scanning tunneling microscopy (STM). In this system sulfur deposition has been obse...
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| Autores principales: | , , , |
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| Formato: | Articulo |
| Lenguaje: | Español |
| Publicado: |
1996
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| Materias: | |
| Acceso en línea: | http://sedici.unlp.edu.ar/handle/10915/126521 https://pubs.acs.org/doi/pdf/10.1021/la940759m?rand=8l3p6czd |
| Aporte de: |
| Sumario: | The early stages of sulfur deposit growth on highly oriented pyrolytic graphite (HOPG) caused by HS- electrooxidation in a neutral buffered solution have been investigated using electrochemical techniques and ex situ scanning tunneling microscopy (STM). In this system sulfur deposition has been observed at −0.80 V vs SCE, i.e. a potential more negative than the reversible potential for the HS-/S reaction. The charge density was equivalent to an average surface coverage by sulfur atoms θ ≅ 1/3 monolayer (ML). Ex situ atomic resolution STM images of the layer electrodeposited at −0.8 V show sulfur submonolayers and large uncovered HOPG domains. Sulfur electroadsorption layers appear as a diluted (√3×√3) surface phase with S atoms atop C atoms of the graphite hexagons and the S−S interatomic distance d(S−S) = 0.42 nm. Further addition of S atoms to a diluted sulfur phase resulted in the formation of sulfur trimers with three S atoms placed atop the three C atoms constituting the graphite hexagons. In this case d(S−S) = 0.24 nm. Neighbor trimers originate a filled hexagonal lattice. Ex situ STM images of overpotential deposited sulfur also show submonolayer sulfur domains with a second hexagonal (√3×√3)R30° sulfur lattice with d(S−S) = 0.42 nm. A further increase of θ produces either a new honeycomb lattice with d(S−S) = 0.24 nm or a rectangular lattice formed by rows of S atoms with d(S−S) = 0.21 nm and row separation d(S−S) = 0.37 nm. |
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