Towards Efficient Oxygen Reduction Reaction: One-Step Synthesis of Co-N Catalysts with Polyhexamethylene Guanidine as Nitrogen Precursor

Developing non-noble metal catalysts that exhibit oxygen reduction reaction (ORR) activity comparable to or exceeding that of platinum-based catalysts remains a significant challenge. This research presents the successful fabrication of novel cobalt-nitrogen (Co-N) catalysts through a straightforward one-step synthesis method. This method involves stirring a mixture of cobalt (II) nitrate, polyhexamethylene guanidine (PHMG) as a nitrogen source, and carbon spheres at ambient temperature. By varying the mass ratio of PHMG to cobalt salt, three distinct catalyst formulations were produced. The catalyst with an optimal PHMG-to-cobalt nitrate ratio of 2:1 (Co-PHMG-2@C) exhibited exceptional electrocatalytic activity for the oxygen reduction reaction (ORR) in alkaline electrolytes. This catalyst demonstrated a high onset potential of 0.97 V and a half-wave potential of 0.82 V versus the reversible hydrogen electrode (RHE), favorably comparable to those of the benchmark Pt/C catalyst (1.02 V vs. RHE). Furthermore, Co-PHMG-2@C displayed superior stability and resistance to methanol poisoning. The scalability of this synthesis technique offers a promising pathway for cost-effective and environmentally friendly production of carbon nanomaterials for applications in fuel cells and other electrochemical energy devices.