Synthesis of active iron-based electrocatalyst for the oxygen reduction reaction and its unique electrochemical response in alkaline medium

Efficient iron-based electrocatalyst for the oxygen reduction reaction (ORR) in alkaline medium was synthesized by facilely modifying single-walled carbon nanotubes (SWCNTs) with iron tetrasulfophthalocyanine (FeTSPc). The resulting FeTSPc/SWCNTs composite was characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV–vis absorption spectrum, Fourier transform infrared spectroscopy (FTIR) and Raman spectrum, which confirmed that FeTSPc could be strongly supported onto SWCNTs through π–π interaction. Cyclic voltammetry and rotating disk electrode results revealed that the ORR catalyzed by FeTSPc/SWCNTs presented a direct four-electron pathway with a very positive onset potential (+0.05 V vs Ag/AgCl, 3 M KCl), cathodic peak potential (−0.10 V vs Ag/AgCl, 3 M KCl) and a large kinetic rate constant (2.31 × 10−2 cm s−1). Besides, FeTSPc/SWCNTs displayed an even better specificity, long-term stability, tolerance to methanol crossover effect and resistance toward CO poisoning effect than the commercial Pt/C catalyst (40%). Further, the catalytic mechanism of ORR and the unique electrochemical behavior of the active sites in FeTSPc/SWCNTs were also been elucidated.