Research On I/C Impacts The Oxygen Reduction Performance Of Catalyst

Proton exchange membrane fuel cell is a kind of clean and environmental protection power systems.Pt catalyst with high loads is an important factor which causes the high cost of the cell.current lower catalyst Pt loads is one of the main direction of catalyst research.Whether using binary and ternary alloy catalysts to replace Pt/C catalyst or preparation of new type membrane electrode,their fundamental purpose is to increase the catalytic activity of Pt and improve the utilization rate of Pt under the condition of limited content of Pt.This paper first prepared Pt nanoparticles with good dispersibility by the method of electrochemical deposition as a kind of low Pt electrode,studied the deposition process impact on the size of the nanoparticles,and get the following conclusions:(1)Compared the substrate and depositing process impacting on the size and morphology of Pt nanoparticles by electrochemical methods.Pt nanoparticles are big obtained by potentiostatic deposition.we got Pt nanoparticles about 10 nm on the glassy carbon by pulse current deposition.In fact,the utilization ratio of Pt catalyst is low.In order to study the factors which affect the activity of Pt catalyst in proton exchange membrane fuel cell,this article respectively took Pt/C electrode and membrane electrode as the research object and mainly studied how the I/C ratio in the electrode affect the catalytic activity of low Pt electrode and get the following conclusions:(2)In the preparation process of catalyst,changing the I/C ratio does not change the electrochemical activity area and the corresponding roughness factor of the electrode.It shows that the existence of nafion will not affect the activity sit of catalyst on the electrode without gas.(3)In the catalyst ink,when I/C is small,the content of nafion does not affect the oxygen reduction activity of catalyst,including limiting current and current density under 0.9 V voltage.However,when the I/C ratio increased to more than 0.4 or greater,the oxygen reduction activity of catalyst will be significantly reduced with the increase of the content of nafion.It shows that when the content of nafion is too much,then it will hinder the transmission of oxygen,which reduces the rate of oxygen reduction reaction and reduces the utilization of Pt.(4)Different from the result on the rotating disk,the I/C has a best value in membrane electrode of fuel cell.The I/C ratio is too low or too high all will lead to a drop in performance of fuel cell.In this paper,it is concluded that the I/C ratio of 0.8 is most appropriate in membrane electrode,the performance,power density and internal resistance are all the best.The reason is that there is no liquid electrolyte in fuel cell environment and only the solid electrolyte which is ionomer can conduct the proton.So,from the perspective of the oxygen transfer,lower I/C ratio is better;But from the perspective of conducting proton,higher I/C ratio is better.Integrating two factors resulted in the best I/C ratio.(5)For different I/C of membrane electrode,the electrochemical active area is basically the same,but the active area is reduced when the I/C is 1.2.The reason may be that too much nafion in the catalytic layer results in decrease of electrical conductivity of the electrode,which leads to the decrease of the active area.