Microelectrode-based hydrogen peroxide detection during oxygen reduction at Pt disk electrode

We investigated the diffusion process of H 2O 2 generated during O 2 reduction at a Pt microdisk electrode used as a generator for scanning electrochemical microscopy (SECM). First, the amount of O 2 consumption and generated H 2O 2 at the Pt generator electrode are estimated using a detector electrode installed in the SECM. Based on the results, a large amount of O 2 consumption and generated H 2O 2 are detected at the center of each generator electrode. According to the measurement, the O 2 starvation and H 2O 2 detection currents can be defined. Subsequently, the O 2 starvation and H 2O 2 detection currents are measured by varying the generator size. As a result, these currents decrease with a decrease in the generator electrode size, however, the H 2O 2 diffusion process is changed for the generator diameter of less than 50 μm. Finally, the O 2 starvation and H 2O 2 detection measurements were conducted using a Nafion-coated Pt microdisk electrode. The amount of O 2 consumption is not suppressed, while the amount of generated H 2O 2 decreases with the Nafion layer prepared on the Pt electrode. This result indicates that the thickness of the H 2O 2 diffusion layer in the H 2SO 4 solution is dramatically diminished by coating the Nafion layer on the Pt generator.