CPRM: a new method for quantitative detection of peroxide formation during oxygen reduction using the rotating ring-disc electrode technique

Abstract

A new procedure to detect peroxide formation quantitatively during oxygen reduction using the rotating ring-disc electrode (RRDE) technique is described. The new procedure is called the Cyclic Potential Ring Measurement (CPRM) method. In this technique, the ring electrode is continuously cycled between 850 mV and 1600 mV versus RHE at a sweep rate of 500 mV s . Concurrently, the disc electrode is stepped potentiostatically in the potential region of oxygen reduction. For oxygen reduction on gold, the CPRM technique indicates 100% peroxide formation in the first wave region whereas the conventional RRDE technique indicated only 20 to 30% peroxide formation. The continuous sweeping of the ring electrode in the CPRM technique regenerates continuously a fresh, active ring electrode surface that is less susceptible to interference from low levels of impurities in the solution. Consequently, the CPRM technique provides a more stable, reproducible ring surface for peroxide detection than the conventional technique. To insure that the potential sweeping of the ring does not affect its response adversely, we measured the electrode collection coefficient with a model system (Fe(CN) 3− 6/Fe(CN) 4− 6), in which low levels of solution impurities would not interfere. The collection coefficient measured using the CPRM and conventional techniques with the model system agreed within ±2.4%.