Metal Oxide (Co(3)O(4) and Mn(3)O(4)) Impregnation into S, N-doped Graphene for Oxygen Reduction Reaction (ORR)

To address aggravating environmental and energy problems, active, efficient, low-cost, and robust electrocatalysts (ECs) are actively pursued as substitutes for the current noble metal ECs. Therefore, in this study, we report the preparation of graphene flakes (GF) doped with S and N using 2-5-dimercapto-1,3,4-thiadiazole (S(3)N(2)) as precursor followed by the immobilization of cobalt spinel oxide (Co(3)O(4)) or manganese spinel oxide (Mn(3)O(4)) nanoparticles through a one-step co-precipitation procedure (Co/S(3)N(2)–GF and Mn/S(3)N(2)–GF). Characterization by different physicochemical techniques (Fourier Transform Infrared (FTIR), Raman spectroscopy, Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD)) of both composites shows the preservation of the metal oxide spinel structure and further confirms the successful preparation of the envisaged electrocatalysts. Co/S(3)N(2)–GF composite exhibits the best ORR performance with an onset potential of 0.91 V vs. RHE, a diffusion-limiting current density of −4.50 mA cm(−2) and selectivity for the direct four-electron pathway, matching the results obtained for commercial Pt/C. Moreover, both Co/S(3)N(2)–GF and Mn/S(3)N(2)–GF showed excellent tolerance to methanol poisoning and good stability.