Cobalt Embedded N‐Doped Carbon Spheres Derived From Cassava Starch for Enhanced Oxygen Reduction Reaction in Alkaline Medium

ABSTRACT Cathodic oxygen reduction reaction (ORR) is essential for fuel cells and metal‐air batteries. The sluggishness of ORR necessitates the synthesis of effective and durable catalysts to intensify the reaction process without compromising cost‐effectiveness. Here, cobalt and cobalt oxides were embedded on N‐doped carbon microspheres (Co─N─C/CS) using cassava starch as a carbon source. The catalyst exhibits a surface area of 388.73 m 2 g −1 , with a predominantly mesoporous texture. The presence of the Co─N bond, along with pyridinic and graphitic nitrogen, contributes to the ORR activity by enhancing the density of active sites. The catalyst achieves a limiting current density of −4.64 mA cm −2 with an onset potential of 0.91 V (vs RHE). The calculated electron transfer value of 3.74 indicates the 4e‐ pathway ORR mechanism supported by Co─N─C/CS. Moreover, the catalyst demonstrates a high stability in 0.1 M KOH with 99% of current retention after 14 000 s, exceeding commercial Pt/C. Relatively high methanol tolerance was also observed for Co─N─C/CS by the addition of 3 M methanol in the electrolyte during current‐time response, highlighting its suitability as a cathode catalyst for direct methanol fuel cells (DMFC).