Introduction to Surface Chemistry and Catalysis by Gabor A. Somorjai & Yimin Li

Author:Gabor A. Somorjai & Yimin Li [Somorjai, Gabor A.]
Language: eng
Format: mobi
Publisher: Wiley
Published: 2011-06-09T16:00:00+00:00

5.6.2 The Solid–Solid Interface

When two different metal surfaces are brought into contact, the surface space charges that were present at their interfaces with a vacuum will be modified. The electrons from the metal of lower work function will flow into the other metal until an interface potential develops that opposes further electron flow. This is called the contact potential and is related to the work function difference of the two metals (Fig. 5.7). The contact potential depends on the materials that make up the solid–solid interface, as well as on the temperature. This temperature dependence is used in thermocouple applications, where the reference junction is held at one temperature while the other junction is in contact with the sample. The temperature difference induces a potential (called the Seebeck effect), because electron flow from the hot to the cold junction. The potential can be calibrated to measure the temperature. Conversely, the application of an external potential between the two junctions can give rise to a temperature difference (Peltier effect) that can be used for heat removal (refrigeration).

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