Nitrogen-doped Carbon Constructed Stable And Highly Dispersed Noble Metal Catalytic System For Glycerol Electrooxidation

As a key component of fuel cells,noble metal-based catalysts have attracted much attention for a long time because of their good catalytic activity.However,to realize its commercial usage successfully,it is necessary not only to pay attention to its catalytic activity,but also to improve its stability and reduce its cost.Therefore,"how to reduce the loading of noble metals and thus reduce the cost of catalysts under the premise of improving the catalytic performance of catalysts" has become a problem that needs to be solved urgently.Researchers have done a lot of research and efforts to find that reducing the particle size of precious metal particles can expose more surface atoms and have lower coordination number,showing a larger electrochemical active surface area.Thus the catalytic activity of the catalyst is enhanced and the utilization efficiency of the unit precious metal is improved.However,when the particle size is very small,the noble metal particles are not easily anchored on the common carbon carrier,and the stability of the catalyst decreases due to the agglomeration between the components.Therefore,it is of far-reaching significance to develop and study catalytic systems with low noble metal loadings and high catalytic activity while maintaining good stability.In this dissertation,the main purpose of the preparation of highly efficient and low-cost fuel cell anode catalysts is to reduce the amount of noble metal used as the starting point,combined with the excellent performance of functionalized support,in order to obtain an ultra-dispersed noble metal catalyst system which was constructed with nitrogen-doped carbon support.Firstly,the catalytic effect of nitrogen-doped porous carbon support on Pd Cu alloy in electrooxidation of glycerol was studied.Then,the preparation process of ultra-dispersed Pt Pd particles was studied.Finally,both nitrogen-doped support and ultra-dispersed structures were introduced.In the final catalyst,a nitrogen-doped support supported ultra-dispersed noble metal catalyst system was successfully constructed and applied in the electrooxidation of glycerol.In these three parts,physical tests were used to characterize all the prepared catalysts.And their electrochemical performance were examined with electrochemical tests.Part I: Pd3 Cu coupling with nitrogen-doped mesoporous carbon to boost performance in glycerol oxidationIn this part,the nitrogen-doped porous carbon support was successfully prepared by template assisted method,and the Pd Cu alloy was supported by polyol assisted method.The Pd3Cu/NMC electrocatalyst was obtained and applied for the electrooxidation of glycerol.The results show that Pd3Cu/NMC exhibits higher oxidation peak current,better stability and lower activation energy than Pd/C in electrocatalytic glycerol oxidation under the same test conditions.This is due to the strong superposition effect between nitrogen doping,mesoporous structure and alloy interaction.The results prove that the nitrogen-doped carbon support is effective in anchoring noble metal nanoparticles.Part II: Carbon-supported efficient ultra-small Pt Pd particles as electrocatalyst towards glycerol electrooxidationIn this part,Pt Pd nanoparticles with small particle size and high dispersion were successfully prepared by acid etching,and supported on carbon support as an effective electrocatalyst for the catalytic electrooxidation of glycerol.The results of physical characterization show that the particle size of the catalyst is about 0.6 nm.Electrochemical tests show that the catalytic performance of Pt Pd-6/C not only exhibits the highest mass activity and stability,but also shows the best CO tolerance due to the combination of the advantages of small particle size and alloy effect.The effective method of preparation of ultra-small particles is explored through this part,and it is also proved that reducing the particle size of noble metals can effectively improve the utilization efficiency of unit noble metal.Part III: Amorphous ultra-dispersed Pt clusters supported on nitrogen functionalized carbon as a catalyst for glycerol electrooxidationIn this part,combining the advantages of nitrogen-functionalized support and ultra-dispersed Pt,the ultra-dispersed electrocatalyst AU-Pt/PMC is successfully synthesized by strict etching process.Physical characterization showed that the catalyst had amorphous structure.The results show that the AU-Pt/PMC electrocatalyst has about 24.3 times stability and 5.1 times activity compared with commercial Pt/C in the electrocatalytic oxidation of glycerol.This good performance can be explained by the unique superdispersion structure of the catalyst and the superposition effect between the platinum cluster and the strong metal-support interaction of PMC.This part of the experiments achieved the stabilization of ultrasmall particles through the stabilization of the new support,which provided the resulting catalyst good catalytic performance.It also shows that it is of great practical significance to construct a new catalytic system based on it.