OSCILLATORY BEHAVIOR IN THE ELECTROCHEMICAL OXIDATION OF FORMIC-ACID ON PT(100)

The electrochemical oxidation of formic acid on Pt was studied in acidic supporting electrolyte using single-crystal electrodes. Very well-defined periodic (not chaotic) current oscillations on a stationary Pt(100) electrode were observed under both potentiodynamic and potentiostatic conditions. The oscillatory behavior is strongly dependent on the Pt surface structure and is seen on the (100) surface but not on the (111) surface. The periodicity, the amplitude, and the absolute magnitude of the current oscillations depends on at least three variables, electrode potential and potential history, formic acid concentration, and the anion of the supporting electrolyte. The pH of the electrolyte was not found to be an important variable, nor was mass transport, e.g. rotation or stirring. The behavior is extremely complex and difficult to analyze in terms of known electrode processes.