Fig. 5. (a) Cathodic polarization curve of Co@NPC and a commercial Pt/C catalyst, performed at a scan rate of 5 mV s−1 in 1 M NaOH solution; (b) Tafel plots for Co@NPC and Pt/C; (c) durability test for Co@NPC through CV before and after the 1000th cycle; (d) chronoamperometric test for Co@NPC, performed at a constant potential.
