Cobalt/nitrogen doped porous carbon as catalysts for efficient oxygen reduction reaction: Towards hybrid enzymatic biofuel cells

Electrochemical oxygen reduction reaction (ORR) represents a crucial cathodic process of different fuel cells. The development of highly active and stable noble metal-free ORR electrocatalysts remains as one of major challenges. Herein, we report cobalt/nitrogen co-doped porous carbon materials (Co-N-C) originated from well-designed bimetal-organic frameworks (Zn100-xCox-ZIF) as efficient ORR electrocatalysts in both pH-neutral and alkaline solutions. The compositional and structural features, and the corresponding ORR activity can be tailored by tuning the Zn/Co ratio in the precursor. Remarkable features of large surface-area and suitable graphitization degree and well-dispersed Co-N-C moieties, enable a high catalytic efficiency. The optimized electrocatalyst registers considerable ORR performance with a high half-wave potential of 0.65 V vs RHE and a saturated current density of 5.30 mA cm−2 close to the value of the commercial Pt/C in 0.1 M pH 7.0 PBS, along with considerable operational stability and tolerance to glucose. A preliminary one-compartment hybrid glucose/O2 enzymatic biofuel cell, consisting of the Co-N-C-10 abiotic cathode and a glucose oxidizing bioanode, is constructed and tested. Furthermore, Co-N-C presents reasonable ORR electrocatalytic activity and operational stability in alkaline condition.