A Composite of Pyrrole-Doped Carbon Black Modified with Co₃O₄ for Efficient Electrochemical Oxygen Reduction Reaction

Low-cost catalysts with high performance toward the oxygen reduction reaction (ORR) in energy conversion systems are intensively desired. Here, we report the preparation of a composite catalyst that is composed of pyrrole-doped carbon black (py-CB) and Co₃O₄ nanoparticles (NPs). The synergetic effect of Co₃O₄ and pyrrole on CB particles endows the obtained py-CB/Co₃O₄ hybrid with pronounced catalytic activity toward the ORR. The onset potential of the hybrid is 0.88 V vs. RHE and the half-wave potential is only 60 mV negative from that of the commercial Pt/C catalyst. The diffusion-limit current density of this catalyst reaches 5.47 mA cm⁻², which is very close to that of Pt/C. The electron-transfer number of ORR on the py-CB/Co₃O₄ is 3.9, indicating a desirable four-electron reduction pathway. Moreover, the hybrid catalyst exhibits a much higher durability toward the ORR than the commercial Pt/C catalyst. The py-CB/Co₃O₄ composite catalyst is highly competitive compared to other carbon-based catalysts, owing to its high activity, excellent stability, and especially the use of inexpensive CB and the ease of preparation. This work may open a new avenue for the design and preparation of ORR catalysts based on cheap and commercially available CB.