Electrochemical Deposition and Re-oxidation of Au at Highly Oriented Pyrolytic Graphite. Stabilization of Au Nanoparticles on the Upper Plane of Step Edges

Journal Article · Wed Oct 01 04:00:00 EDT 2003 · Journal of Physical Chemistry B

OSTI ID:912014

Pinhero, Patrick Joseph; Lister, Tedd Edward; Boxley, Chett J; White, Henry S

The electrochemical deposition and reoxidation of Au on the basal plane of highly oriented pyrolytic graphite (HOPG) immersed in a 5 mM AuCl4-/6 M LiCl solution is reported. Scanning electron microscopy (SEM) and ex-situ atomic force microscopy (AFM) demonstrate that Au nanoparticles, ~3.3 nm in height and ~10 nm in diameter, are deposited at times less than ~1 s. The density of nanoparticles, 6 × 109 cm-2, is of the same order of magnitude as the surface point defect density, suggesting that point defects act as nucleation sites for Au electrodeposition. A small subset of the Au nanoparticles (~7%) continues to grow between 1 and 50 s, reaching a height of ~150 nm and a diameter of ~300 nm. At times greater than 50 s, the larger particles coalesce to yield a surface comprised of a low density (~2 × 106 cm-2) of micrometer-size Au crystallites surrounded by Au nanoparticles. Double potential step chronocoulometric experiments demonstrate that the electrodeposition of Au is chemically irreversible, a finding supported by SEM and AFM observations of Au nanoparticles and larger crystallites on the surface after long periods of reoxidation (>3600 s). Au nanoparticles are observed to be preferentially deposited on the upper plane of step edges, a consequence of the nonuniform surface electron density that results from relaxation of the graphite lattice near steps.

• Research Organization: Idaho National Laboratory (INL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC07-99ID13727
• OSTI ID: 912014
• Report Number(s): INEEL/JOU-02-00816
• Journal Information: Journal of Physical Chemistry B, Journal Name: Journal of Physical Chemistry B Journal Issue: 2 Vol. 107
• Country of Publication: United States
• Language: English

Related Subjects

99 GENERAL AND MISCELLANEOUS
ATOMIC FORCE MICROSCOPY
Au
DEPOSITION
ELECTRODEPOSITION
ELECTRON DENSITY
GRAPHITE
NUCLEATION
POINT DEFECTS
RELAXATION
SCANNING ELECTRON MICROSCOPY
STABILIZATION
electrochemical deposition
nanoparticles
pyrolytic graphite
reoxidation