SURFACE-REACTIONS WITH HOT-ELECTRONS AND HOT HOLES IN METALS

Electrochemical reactions (oxidation or reduction) start when the electronic levels of the redoxsystem within the electrolyte cross the Fermi level E-F of the electrode - from below to above E-F in the case of the oxidation and from above to below in the case of reduction. This energetic shift of the redox level is effected by changing the electrochemical potential of the electrode. Hot electrons above E-F or hot holes below E-F incident at the metal-electrolyte interface from the metal side may induce reduction and oxidation, respectively, at electrochemical potentials where no reactions occur with the electrode in its electronic ground state. This is related to surface photochemistry, believed to be induced by intermediate hot electrons. In the present work hot electrons and hot holes are injected into a thin silver film electrode by tunnelling within a metal-insulator-silver contact. The results presented here confirm the new unusual reactions, provided there is either atomic scale roughness or a suitable redox level at the silver-electrolyte interface.