Figure 4.

(A) Pt-group-metal (PGM)-free oxygen reduction reaction (ORR) catalyst, N-TaTiOx/C, was immobilized with 6CFL and Nafion® on an indium-tin oxide (ITO) electrode, and an inverted microscope was used to monitor the fluorescence spectra of 6CFL. The measured fluorescence spectrum is shown. (B) ORR polarization curve of N-TaTiOx/C dispersed on a Nafion® film with oxygen-saturated 0.1 M H₂SO₄ electrolyte at a scan rate of 10 mV/s. (C) Fluorescence decay of 6CFL with and without 5% H₂O₂ added in the electrolyte solution in the theta capillary (no catalyst present on ITO). (D) Fluorescence decay of 6CFL measured using Ar and O₂-saturated 0.1 M H₂SO₄ electrolyte with N-TaTiOx/C on ITO. The working electrode potential was maintained at 0.3 V vs. reversible hydrogen electrode (RHE).