CO Methanation and Ethane Hydrogenolysis over Ni Thin Films Supported on W ( 110 ) and W ( 100 )

Conclusions The application of the mixed monolayer approach to gold electrodes coated with highly organized long-chain hydrocarbon amphiphiles enables us a t this point to obtain complete blocking of the electrode, or, by controlling the adsorption conditions, to leave a certain amount of natural pinholes. Both cases are of considerable interest from an electrochemical point of view. In the present work we have exploited the latter possibility, Le., the electroactive pinholes in Au/monolayer electrodes with 0 close to (but less than) unity. Such electrodes provide unique arrays of ultramicroelectrodes with an average diameter of 5-10 nm, probably the smallest microelectrodes which have so far been characterized and used. It was shown that Au/monolayer electrodes can effectively facilitate various electrochemical measurements, including kinetic studies of very rapid electrode reactions. We have used such electrodes for the determination of several very large heterogeneous rate constants ko, the highest being 5.0 cm/s. However, ko values greater than 10 cm/s can be measured quite conveniently with the present system. A complete blocking of electrodes with a single organized monolayer will be important in electrochemical experiments involving electron transfer via electron tunneling, as well as the future implementation of selective ionic or electronic conductivity in organized monomolecular systems. These directions are presently pursued in our laboratory.