An Electrocatalyst Derived from Graphitic Carbon Nitride–Metal Organic Framework Hybrid for Efficient Electrochemical Oxygen Reduction Reaction

Transition metal nanoparticles embedded in heteroatom-doped carbon nanostructures demonstrate excellent catalytic activity in energy conversion applications as opposed to platinum group metals (PGMs). Here, we report the design of a Co nanoparticle encapsulated within an N,S dual-doped carbon nanofiber (Co@NSCNF) obtained from an N,S-codoped g-C3N4–MOF (ZIF-67) composite precursor for an efficient electrochemical oxygen reduction reaction (ORR). The unique combination of the composite precursor facilitates N,S dual doping in a defect-rich carbon nanostructure with enhanced porosity, which further boosts the ORR activity in both alkaline and acidic media. The Co@NSCNF (TS) catalyst obtained from thiosemibarbazide (TS)-derived g-C3N4 demonstrates superior ORR activity with E1/2 ≈ 0.871 V vs RHE and stability in 0.1 M KOH, surpassing Pt/C (20 wt %). Furthermore, the catalyst exhibits very good 4e- selectivity with n ≥ 3.8 in the potential range of 0.2–1.0 V. The catalyst, owing to its robust nature, retains >94% of its current during the current–time response test at 0.8 V for 25 h and shows excellent tolerance to methanol crossover. The Co@NSCNF (TS) catalyst with its superior ORR performance can be a potential alternative to PGM-based catalysts for renewable energy applications.