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

We investigated the diffusion process of H₂O₂ generated during O₂ reduction at a Pt microdisk electrode used as a generator for scanning electrochemical microscopy (SECM). First, the amount of O₂ consumption and generated H₂O₂ at the Pt generator electrode are estimated using a detector electrode installed in the SECM. Based on the results, a large amount of O₂ consumption and generated H₂O₂ are detected at the center of each generator electrode. According to the measurement, the O₂ starvation and H₂O₂ detection currents can be defined. Subsequently, the O₂ starvation and H₂O₂ 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 H₂O₂ diffusion process is changed for the generator diameter of less than 50 μm. Finally, the O₂ starvation and H₂O₂ detection measurements were conducted using a Nafion-coated Pt microdisk electrode. The amount of O₂ consumption is not suppressed, while the amount of generated H₂O₂ decreases with the Nafion layer prepared on the Pt electrode. This result indicates that the thickness of the H₂O₂ diffusion layer in the H₂SO₄ solution is dramatically diminished by coating the Nafion layer on the Pt generator.