Fig. 3.

Half-cell characterization of the catalysts. Linear sweep voltammetry curves of graphene nanoribbons on carbon nanotubes (GNR@CNT), N-doped GNR@CNT (N-GNR@CNT), and N-doped graphene nanoribbons (N-GNR) for a oxygen reduction reaction (ORR) activity, b peroxide reduction reaction (PRR) activity with 1.3 or 10 mM H₂O₂, and c ORR activity at 5, 25, and 35 °C in 0.1 M KOH; d ORR activity, e PRR activity with 1.3 or 10 mM H₂O₂, and f ORR activity at 5, 25, and 35 °C in 0.5 M H₂SO₄. Electrolyte was O₂-saturated, except for PRR experiments with Ar-saturated electrolyte. Rotating speed: 1600 rpm. Scan rate: 10 mV s⁻¹