OXIDATION OF FORMIC-ACID IN ACID-SOLUTION ON PT SINGLE-CRYSTAL ELECTRODES

The electrodes, particularly the Pt(100) plane. Focusing on the analys is of the voltammetric profiles, the effects of the experimental condi tions (formic acid concentration, upper and lower potential limits of the sweep, sweep rate, solution pH etc.) were examined extensively. Th e product survey was performed using the newly developed on-line diffe rential electrochemical mass spectrometry (DEMS). The following result s were obtained. (1) The surface species X(1) (linearly bonded CO) for med mainly in the hydrogen region and retarded the reaction strongly u p to ca. 0.8 V in the positive-going scan. When the X(1) coverage is l ower, the reaction occurred with a peak P-1 at ca. 0.4 V (process I). (2) After the removal of X(1) at ca. 0.8 V (peak P-2), no reaction occ urred up to a potential of 1.0 V, suggesting the presence of retarding process. (3) When the potential was reversed at 1.0 V, the retarding process remained beyond 0.8 V in the negative-going scan. The retardin g action decreased exponentially with the negative potential shift, an d correspondingly the reaction was accelerated. (4) The reaction conti nued to occur with a peak P-3 at ca. 0.6 V (process II). With further negative polarization, the reaction ceased beyond 0.3 V with a shoulde r corresponding to P-1 (process I). (5) Another retarding process was observed in the potential region between P-1 and P-3. The species X(2) responsible was electrochemically inactive. The behavior of X(1) and X(2), processes I and II, and the retarding process on Pt(100), togeth er with the DEMS results, were examined in detail.