A newly designed thin-layer cell allows the use of differential electrochemical mass spectrometry (DBMS) for the identification of volatile electrochemical desorption products from single-crystal electrodes. The sensitivity Is In the range of a percent of a monolayer. This Is demonstrated for the case of preadsorbed benzene on a Pt(111) electrode. Contrary to the case of a polycrystalline electrode, benzene Is mainly desorbed as such without H/D exchange; only a minor part Is hydrogenated to cyclohexane, which Is the main desorption product from a polycrystalline electrode. Oxidation of the adsorbate occurs In two well-separated steps: In the double-layer region a partially oxidized adsorbed intermediate Is formed, which Is oxidized to C02 In the oxygen adsorption region.

We describe the construction of a beetle‐type scanning tunneling microscope optimized for in situ measurements. The influence of the crystal preparation technique on the surface structure is reported. Whereas annealing of platinum single crystals in iodine vapour yields smooth surfaces for the low index faces, which are protected from contamination in air by the adsorbed iodine, facetting occurs in the case of stepped surfaces. — The iodine adlattices are resolved both in air and electrolyte: Pt(111) (3 × 3)‐I and Pt(100) (√2 × 5√2)R45°I, thus confirming previous LEED results.

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Amperometric electrochemical gas sensors have the advantage of combining good sensitivity and selectivity at relatively low cost. However, their use is restricted to the detection of gases that are very reactive at potentials positive of that at which oxygen is reduced. We describe here a new detection method for less reactive species such as benzene and halogenated hydrocarbons, which cannot be directly oxidized. Instead, the species is continuously adsorbed at a potential below 0.5 V and then oxidized at potentials where oxygen coadsorbs. The oxidation current is corrected for the oxygen adsorption current by performing an additional potential cycle, in which no adsorption is allowed to occur. We have so far obtained sensitivities in the lower ppm range for benzene, toluene, tetrachloroethene, epichlorohydrin, and vinyl acetate; for saturated halogenated hydrocarbons such as CFCl 3 , it is still below 1000 ppm.