Fe–N/C catalysts synthesized by heat-treatment of iron triazine carboxylic acid derivative complex for oxygen reduction reaction

Abstract

4,4′,4′′-s-Triazine-1,3,5-triyltri-p-aminobenzoic acid (H₃TATAB) was used as a ligand to prepare an iron–TATAB (Fe–TATAB) complex for the development of an effective oxygen reduction reaction (ORR) catalyst. The activity of the catalyst depended on weight ratios between the Fe–TATAB complex and carbon black and heat-treated temperatures. The results showed that the Fe–N_70%/C-800 catalyst (the weight ratio of Fe complex to carbon black was 70 : 30 and the catalyst was pyrolyzed at 800 °C) had good catalytic activity toward ORR with the onset potential at 0.91 V vs. RHE and a kinetic current density of 4.3 mA cm⁻² at 0.6 V vs. RHE in alkaline medium. Moreover, the Fe–N_70%/C-800 catalyst had better tolerance to methanol crossover effect in comparison with commercial Pt/C (20%). The morphology and composition of the catalysts were characterized by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) as well as X-ray photoelectron spectroscopic (XPS). The electrocatalytic activities were demonstrated by cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometric measurements and stability accelerated tests. According to rotating disk electrode (RDE) measurements and Koutecky–Levich analysis, the overall electron transfer number in the catalyzed ORR was found to be 3.7–3.9 and the ORR process was mainly a four-electron pathway. The results indicate that the Fe–N_70%/C-800 catalyst may be a promising cathode catalyst for ORR.