Studies On Electrospun Carbon Nanofibers And Its Electrocatalytic Properties

Proton exchange membrane fuel cell?PEMFC?is a kind of new energy technology,with extensive application prospects.But high cost and poor durability of noble metal catalysts hinder the commercialization.Moreover,the carbon powder support is prone to agglomeration,corrosion and leads to poor conductivity and high mass transfer resistance.In order to solve these problems,this thesis introduces new nano carbon fiber prepared by electrospinning with large surface area,high porosity and good conductivity.The effects of polymer type and mass fraction,spinning voltage,speed,distance,temperature,humidity and other factors on the morphology and properties of carbon fiber are studied.Based on polymer fiber material,Pt/CNF?carbon nanofiber,CNF respectively?and Fe/N/CNF catalysts are prepared by one-step electrospinning method.The main conclusions are as follows:?1?Polymer species determine the basic properties of the fiber material.Among PVP,PVA,PAN and PI polymer materials,the performances of the spun and carbonized fibers of PAN and PI are best,having the specific surface area of 535 and572 m²/g,respectively.The PVP fiber are most easy to prepare,but the carbonized fiber are weaker and the specific surface area is lower.?2?Pt/CNF catalysts were successfully prepared by electrospinning H₂Pt Cl₆/PVP solution,the specific surface area of the catalyst is about 290 m²/g and the Pt loading is about 18 wt.%,the catalyst shows excellent activity for oxygen reduction reaction,with0.71 V for the half-wave potential.?3?A series of Fe/N/CNFs catalysts with different iron loadings were prepared by pyrolysis of PI nanofibers loaded with Fe and N precursors.The catalyst with 3 wt.%Fe loading shows the highest activity towards oxygen reduction reaction dominated by the four electron process.The fiber diameter is between 200³00 nm,and the specific surface area of the Fe/N/CNFs-3 catalyst is 447 m²/g.The initial and half-wave potentials of Fe based catalysts are 13.7 and 100.1 mV lower than that of the commercial Pt/C respectively.Moreover,the Fe based catalysts only have 13.4 and 76.3mV negative shifts after 5000 cycles,but 114.7 and 270 mV for Pt/C,respectively.It indicates that the Fe/N/CNF electrocatalyst possesses high activity and excellent electrochemical stability.