| Proton exchange membrane fuel cells（PEMFCs）can convert chemical energy into electric energy in an efficient,environmentally friendly and zero emission way,provide an effective way to deal with energy crisis and environmental pollution.However,carbon,commonly used as support for PEMFCs electrocatalyst like Pt/C,are prone to be corroded resulting in reduced performance of PEMFCs.In particular,the corrosion of carbon was increased significantly during start-stop cycles or when reversed voltage happened,the potential normally reached over 1.5 V.To overcome it,CeO2,often used as free-radical scavenger,which show good stability under high potential and strong interaction with platinum,was supported on carbon to form composite.As carbon with high specific surface area is highly electro-conductive,the composite（CeO2/C）,out of the poor electroconductivity of CeO2,can be an ideal support for Pt based catalyst.In this paper,nitrogen doped carbon support materials were prepared with dopamine（DOPA）as nitrogen source,and the nitrogen content and type were characterized by X-ray photoelectron spectroscopy.CeO2 was deposited on the surface of nitrogen doped carbon to prepare CeO2/C composite supports.Finally,platinum nanoparticles were uniformly deposited on the support by methanol reduction method to obtain nano platinum catalyst.The structure and micro morphology of the catalysts were characterized by X-ray diffraction and transmission electron microscope,and the catalytic activity and durability of the catalyst for ORR were characterized by RRDE technique.The specific research contents are as follows:（1）Nitrogen doped carbon materials were prepared with DOPA as nitrogen source.The nitrogen content can be controlled from 1.0 to 3.5 at.%by adjusting the ratio of dopamine to carbon matrix XC-72;The uniformly dispersed CeO2 nanoparticles were deposited on nitrogen doped carbon carrier by alkali precipitation method.Except for a small amount of agglomerated particles,the grain size of CeO2 nanoparticles was about 1～3 nm.After heat treatment at 600℃,the grain size of CeO2 nanoparticles increased to 2～4 nm.（2）The Pt/NC catalysts were prepared by using methanol as reductant to reduce chloroplatinic acid on nitrogen doped carbon.The transmission electron microscope showed that the dispersed Pt nanoparticles had a particle size of 2～4 nm.With the increase of nitrogen content,Pt dispersed more evenly on the surface of the support,but there were still many largely agglomerated particles.The XRD results showed that the average particle size of platinum was about 5.6 nm.Adjusting methanol concentration,sodium citrate content and adding ethylene glycol can further improve the dispersion uniformity of Pt on carbon.The average grain size of platinum nanoparticles decreased from 5.6 nm to 3.3 nm,indicating that the dispersion of platinum has been greatly improved.（3）The mass specific activity of Pt/NC catalysts for ORR was better than that of commercial Pt/C（JM）,and the high potential corrosion resistance of Pt/NC catalysts was also better than Pt/C.When ethylene glycol was added,the Pt grain size was 3.3 nm,and the ECSA reached 64.9 m2·g-1,which was 24.2 m2·g-1 higher than that of commercial Pt/C.The im@0.9 V reached 248.6 mA·mg-1,which is 44.8 mA·mg-1 higher than that of commercial Pt/C.After 10000 scans at 1.0～1.2 V（vs.RHE）,the im@0.9 V decreased by 18%,while im@0.9 V of commercial Pt/C decreased by 48%.（4）The mass specific activity of Pt nanoparticles deposited on CeO2/NC support was lower than that of Pt/NC catalysts,and the performance of high potential corrosion resistance was further improved.The ECSA of Pt/CeO2/NC-600 is 27.7 m2·g-1,im@0.9 V of Pt/CeO2/NC-600 is 105.2 mA·mg-1,which has a certain gap compared with commercial Pt/C.But after 10000 scans at 1.0～1.2 V（vs.RHE）,the im@0.9 V increased to 114.3 mA·mg-1 and ECSA decreased by 24%,indicating that CeO2/NC supported platinum catalysts had good high potential corrosion resistance. |
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