Chemical Activation of Gold Surface by Mechanical Contacts

Abstract

Tribochemical activation of gold surface is reviewed. When the surface layers such as metal oxides and organic contaminants removed mechanically, nascent surfaces which have defects and dangling bonds are formed. Gold surface was activated by friction in a vacuum chamber, and chemisorption and surface reactions of organic compounds were monitored with a quadrupole mass spectrometer. Gold becomes to be active by mechanical contacts. Compounds such as olefins, aromatics and organic sulfides chemisorbed more easily than polar compounds such as carboxylic acids on the nascent gold surface. Olefins and benzene chemisorbed on nascent gold surface followed by hydrogen evolution as a dehydrogenation product of olefins. The formation rate of hydrogen was proportional to sliding velocity that is formation rate of nascent surface. Hydrogenation of the olefins also observed on nascent gold surface. The dehydrogenation and hydrogenation occurred on nascent gold surface even at room temperature. Surface defects formed by mechanical contacts may act as an active site for the reaction.