VOLTAMMETRY IN THE ABSENCE OF A SOLUTION-PHASE WITH SOLIDS PREPARED BY A SOL-GEL PROCESS AS THE ELECTROLYTES - FACILITATION OF AN ELECTROCATALYTIC ANODIC PROCESS IN THE PRESENCE OF AMMONIA

An interdigitated microelectrode (IME) coated with a glassy polymer of V2O5 by a sol-gel process is demonstrated to serve as a solid electro lyte for voltammetric studies in the absence of a contacting solution phase. The oxidation of iron(II) 1,10-phenanthroline immobilized there in occurs at the same potential as in solution-phase experiments at a Pt working electrode; however, the current limiting process in the sol id-state system is dependent on the time scale of the experiment. Cycl ic voltammetry at scan rates of 0.1 to 1.0 V s(-1) yields currents lim ited by planar diffusion, but below 3 mV s(-1) the peak currents are i ndependent of scan rate. This steady-state behavior in the coated IME is indicative of current limitation by semi-cylindrical diffusion to t he 10 mu m x 5 mm Pt surfaces at slow scan rates; potential step chron oamperometry verifies this interpretation. When one set of Pt fingers in the IME is a quasi-reference and the other set is modified with a p olymeric ruthenium oxide catalyst, the presence of ammonia in the surr ounding gas phase causes an anodic process. Indirect evidence that thi s process is the electrocatalytic oxidation of ammonia is presented. T his anodic behavior is not observed when the voltammetry is performed in a conventional solution cell under otherwise-identical conditions.