The Electrochemical Performance Study Of Nitrogen And Sulfur Doped Porous Carbon Derived From Grafted Polymer

Due to the large specific surface area,excellent chemical and thermal stability,easy processing and good electrical conductivity,porous carbon are widely used in hot areas such as catalysis,adsorption,biosensors,energy storage and energy conversion.Oxygen reduction as one of the three important reactions in renewable energy technologies has sluggish kinetic.Metal catalyst,with high cost,is easy to corrosion and has many other shortcomings.By replacing metal catalyst,Porous carbon can reduce costs and promote the development of fuel cell and metal air battery technology.At present,there are two main approach to improve the electrocatalytic performance of porous carbon:?1?introduction of heteroatoms,a large number of active sites can be produced by the introduction of heteroatoms.?2?Optimizing morphology of the carbon.The porous structure facilitates proton conduction and reactant diffusion,which can improve the catalytic efficiency of porous carbon.Based on this,the following work is done:?1?The nitrogenous polyelectrolyte brushes were used as precursors.After carbonization,the porous carbon was obtained.By comparing the properties of porous carbon prepared by physical mixing,the effect of two kinds of preparation methods on the nitrogen content in porous carbon was studied.?2?Nitrogen-sulfur double doped porous carbon was synthetized by using poly?4-vinylpyridine?brushes as nitrogen source and 2-thiophene acetic acid as sulfur source.By comparing the catalytic performance of porous carbon prepared by different carbonization temperature,the optimum carbonization temperature was gained.?3?Polyelectrolyte brushes with different sizes of silica.The effects of different morphologies on porous carbon was studied by comparing catalytic performance.Conclusions has been drawn as follows?1?Through the BET,TEM test,carbon based on the polymer brush are porous,with the size of pore distribution mainly from 25 nm to 35 nm.The specific surface area of nitrogen-doped porous carbon is 360.566 m2/g.?2?The nitrogen content of porous carbon prepare by polymer brush is 3.07%and the degree doping is lower than that of carbon prepared by physical mixing.The nitrogen element tends to be stable?2.47%at 1000 ^??with the increasing of temperature,but the sulfur decrease sharply when the temperature is too high?1000^??.The elemental analysis of nitrogen-sulfur double-doped porous carbon from different sizes of silica shows that the porous carbon from 15nm has a higher content of nitrogen and sulfur,which are 3.24%and 7.28%,respectively.?3?XPS measurements shows that,the major nitrogen exists as pyridinic N and graphite nitrogen in nitrogen-doped porous carbon,which contributes to 55.8%and20%respectively.With the increasing of temperature,the content of pyridine nitrogen decrease in the nitrogen-sulfur doped carbon,while the graphite nitrogen increase.What's more,the sulfur element is predominantly present in the form of thiophene sulfur.?4?The electrochemical performance of nitrogen-doped carbonaceous materials is better than that of physical mixing by electrochemical test CV and ORR,with onset potential of 0.08V,the half-wave potential of-0.169 V and the limiting current density of 5.08 m/cm².Four-electron reaction is the dominant process for ORR.The durability test showed good electrochemical stability.After 10000 continuous CV cycles,the half-wave potential slightly shifts to the negative side by about 30 mV.The nitrogen-sulfur double-doped porous carbon prepared at 900 ^? show an onset potential of 0.03 V?vs.Hg/HgO?and four electron path for ORR.In addition,durability test results show good electrochemical stability.?5?CV and ORR of porous carbon prepared by different nanoscale templates indicate nitrogen-sulfur double-doped porous carbon prepared by 30 nm SiO₂ has a better electrochemical performance.