Electron transfer at semiconducting metal dichalcogenide/liquid electrolyte interfaces

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:5718970

Howard, J N

Charge transfer at semiconductor/electrolyte interfaces is the critical process in photoelectrochemical systems. Many aspects of the theory for these interfaces have yet to be experimentally verified. There are few reliable measurements of the fundamental electron transfer rate at nonilluminated semiconductors. This situation stems from experimental limitations imposed by most semiconductor electrode surfaces. Layered metal dichalcogenide semiconductors have excellent properties as semiconductor electrodes, but edge sites and crystal defects must be masked so only the defect-free basal plane of the two-dimensional material is exposed to solution. Conventional epoxy encapsulation of the crystal epoxy can introduce deleterious effects. A minielectrochemical cell was developed to perform experiments in a single drop of electrolyte held against the working electrode. The electrochemical behavior and operational considerations of the cell for aqueous and nonaqueous systems were investigated. Spatially-resolved electrochemistry was demonstrated for n-WSe[sub 2] and highly ordered pyrolytic graphite. The minicell was used to investigate electron transfer at nonilluminated n-WSe[sub 2]/dimethylferrocene[sup +/0] interfaces. This semiconductor is resistant to corrosion and has stable interfacial energetics. Interfaces with excellent diode behavior could be obtained by probing different regions of the surface. Electron transfer at these high quality surfaces was studied over an extensive solution concentration range. The rate of electron transfer was independent of solution acceptor concentration from 5 [mu]M to 0.25 M. The electron transfer data can be explained by assuming a surface-state mediate mechanism. A second metal dichalcogenide, n-SnS[sub 2], was investigated to compare the behavior of this wide band gap material to the narrow band gap n-WSe[sub 2]. The n-SnS[sub 2] electrodes displayed undesirable electrochemical effects in several solvent systems.

• Research Organization: Colorado Univ., Boulder, CO (United States)
• OSTI ID: 5718970
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360606 -- Other Materials-- Physical Properties-- (1992-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400400* -- Electrochemistry
CARBON
CHALCOGENIDES
CHEMISTRY
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
ELECTROCHEMISTRY
ELECTRODES
ELECTROLYTES
ELECTRON TRANSFER
ELEMENTAL MINERALS
ELEMENTS
GRAPHITE
INTERFACES
MATERIALS
MINERALS
NONMETALS
REFRACTORY METAL COMPOUNDS
SELENIDES
SELENIUM COMPOUNDS
SEMICONDUCTOR MATERIALS
SURFACES
TRANSITION ELEMENT COMPOUNDS
TUNGSTEN COMPOUNDS
TUNGSTEN SELENIDES