Preparation Of PdCo Catalysts For ORR By Electro-spinning Method

Electrocatalyst is one of the key materials of proton exchange membrane fuel cell(PEMFC), which has important significance on the stability as well as service life and cost, etc. of the PEMFC. Therefore, To develop cathode catalysts with low cost, well stable performance for the PEMFC has both important theoretical significance and application values.In the study, electrocatalysts were prepared by electrostatic spinning method. First nano fibers with Pd and Co ions were synthesized by electrostatic spinning, and then reduced and calcinated under nitrogen atmosphere in a tube furnace. A series of electrocatalysts with different atomic ratio between Pd and Co were fabricated. Field emission scanning electron microscope(FE-SEM),Scanning electron microscope(SEM),X-Ray powder diffraction(XRD), etc. were applied to characterize the influences of spinning solution concentration, spinning voltage and distance on the morphology of nano fibers. The effects of calcination time and temperature on morphology of the electrocatalyst were also studied. The optimal experiment conditions were as follows: When the concentration of PVP in the spinning was 11%, spinning voltage 18 kV and the distance 18 cm, the nano-fibers displayed the best morphology with smooth surface and smallest radius; When calcination temperature was 550℃ and calcination 5 hours, both the morphology and the electrochemical properties of electrocatalysts were the best.Finally electrochemical properties of Pd/C and PdCo/C and mixture of PdCo/C and Pt/C were tested and compared. PdCo/C showed better electrochemical properties than Pd/C, especially the PdCo/C catalyst with an atomic ratio between Pd and Co of 3:1 illustrated the best performance in ORR and excellent methanol tolerance. Mix catalysts of Pd3Co1/C and Pt/C with different mass ratio were also prepared and tested. When the content of Pd3Co1 was smaller than 20% in the mixture, ECS, anti-aging performance and stability of the mix catalyst were all better than those of Pt/C in acidic surrounding. Stability were tested by chronoamperometry. After 2400 s, the current density of Pd3Co1/C(10% wt) and Pt/C mix-catalyst reached 1.30 mA/cm2, while the Pt/C was 0.34 mA/cm2.