Metals, band theory water

Applications have been reported for photoelectrochemical experiments, for example, splitting of water [11], local generation of photoelectrodes by spatially selective laser excitation [12], and steady-state electrochemiluminescence at a band electrode array [13,14]. Band electrodes prepared from very thin films approaching molecular dimensions have been used to assess the limits of theory describing electrode kinetics at ultramicroelectrodes [9]. Spectroelectrochemical applications have been extensively reviewed [1], In an intriguing approach, thin, discontinuous metal films have been prepared on a transparent semiconductor substrate they are essentially transparent under conditions in which a continuous metal film containing the same quantity of metal would be expected to substantially absorb [15]. 

Here, X is th so-called surface potential corresponding with the electrostatic potential step resnlting from the inhomogeneous charge distribution on the surface. This surface dipole can be calculated for metals on the basis of more or less refined theories and depends veiy much on the band stmcture. In order to get some idea of the possible size of snch snrface potentials, one shonld realize that a layer of water molecules with each molecule oriented perpendicular to an atom of a surface with 10 atoms per square centimeter would correspond with a X potential of about 3.8 V. 

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