Semiconductor Electrochemistry and Photoelectrochemistry

The degradation of materials does not only occur with metals but also with semiconductors or insulators. Furthermore, many metals are covered with oxide and hydroxide films, which have semiconductor properties. Therefore concepts have to be developed to treat semiconductor electrochemistry. 

Band model of (a) a metal, (b) intrinsic, (c) n-type, and (d) p-type semiconductor with Fermi energy Ep valence band VB, conduction band CB, and donor and acceptor levels. 

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From a materials perspective, the field of semiconductor electrochemistry and photoelectrochemistry has evolved from the use of semiconductor single crystals to polycrystaUine thin films and, more recently, to nanocrystalline films. The latter have been variously termed membranes, nanoporous or nanophase films, meso-porous films, nanostructured films, and so on they are distinguished from their polycrystalhne electrode predecessors by the crystallite size (nm versus pm in the former) and hy their permeability to the electrolyte phase. These films are referred to as nanocrystalline in the following sections. These features render three-dimensional geometry to nanocrystalline films as opposed to the flat or two-dimensional (planar) nature of single crystal or polycrystalline counterparts. 

Research in the author s laboratory on semiconductor electrochemistry and photoelectrochemistry since 1995 is funded, in part, by the Office of Basic Energy Sciences, the US Department of Energy. A number of talented and dedicated coworkers and colleagues have been involved in collaborative research with the author over the past twenty years their names appear in the publications cited from this laboratory. I also thank the University of Texas at Arlington for providing the facilities and infrastructure. I am grateful to Prof S. Licht for comments on an earlier version of the manuscript. Last but not least, I thank Ms. Gloria Madden and Ms. Rita Anderson for assistance in the preparation of this chapter. 

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