Synthesis of Fe nanoparticles on polyaniline covered carbon nanotubes for oxygen reduction reaction

• We disclosed in situ synthesis to achieve Fe–PANI/CNT structure.
• The regular structure was obtained by pretreating FeCl3 with citric acid.
• These Fe–PANI/CNT structures exhibited beneficial ORR behaviors.
• These Fe–PANI/CNT structures still confront surface red-ox couple and conductive problems exhibited in their high Tafel slopes.

Fe nanoparticles immobilized on polyaniline-covered carbon nanotube (CNT) surfaces (Fe NPs–PANI/CNT) are prepared by reducing FeCl3 in the mixing solution of aniline and CNT. Significantly, the structure of such composites can be effectively optimized by pretreating FeCl3 with sodium citrate (CA). In the absence of CNTs, we found these two routes have large differences in reduction behaviors and different PANI states with varied conductivities. Therefore, the self-assembly mechanism in the preparation is proposed and the controlled self-assembly manner in the pretreating route is disclosed. Under acid condition, both catalysts demonstrate high oxygen reduction reaction (ORR) activity with four-electron pathway, and high electrochemical durability, revealing a promising application in the proton exchange membrane fuel cells. However, the high Tafel slopes relating to the surface red-ox couple and porous conductivity are still the main obstacles to improve their ORR dynamic, and more efforts on these aspects are needed to drive non-noble catalyst application in future.

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