【作者】 李晓峰；

【导师】 张海宁；

【作者基本信息】 武汉理工大学 ， 材料科学与工程， 2017， 硕士

【摘要】 多孔碳材料由于比表面积大,良好的化学和热稳定,易加工和良好的导电性性,而广泛应用于催化,吸附,生物传感器,储能和能量转换等热门领域。氧还原反应作为可再生能源技术中重要的三个反应之一,动力学缓慢,而具有良好氧还原性能的金属催化剂,具有成本高,易腐蚀等许多缺点。多孔碳材料代替金属催化剂,可以降低成本,推动燃料电池和金属空气电池技术的发展。目前,提高多孔碳材料的电催化性能的主要有两个途径:（1）引入杂原子,杂原子的引入产生大量的活性位点,提高碳材料的催化活性,（2）优化碳材料的形貌,更多的孔结构,有利于质子传导和反应物的扩散,提高多孔碳材料的催化效率。本文开展以下工作:（1）以含氮的聚电解质刷为前体,高温碳化来制备掺氮多孔碳。并通过对比物理混合所制备的多孔碳的性质,评价两种制备方法对多孔碳中氮元素的影响。（2）以聚4-乙烯基吡啶刷为氮源,2-噻吩乙酸为硫源,合成氮硫双掺杂多孔碳材料,通过不同碳化温度得到的多孔碳的催化性能,得到最佳的碳化温度。（3）以不同尺寸大小的二氧化硅来合成聚电解质刷,通过研究测试电化学性能,研究不同形貌的对多孔碳的催化性能的影响。得到如下结论:（1）通过BET,TEM的测试,基于聚合物刷的碳材料均为多孔结构,孔径分布主要在25 nm-35 nm。利用接枝技术所制备的氮掺杂多孔碳比表面积为360.5660 m2/g。（2）通过元素分析测试,利用接枝技术所制备的多孔碳氮元素含量为3.07%,掺杂程度低于物理混合碳材料的。不同碳化温度所制备的氮硫双掺杂碳的元素分析中,温度越高,氮元素逐渐趋于稳定（在1000 ^℃含2.47%）,硫元素在温度过高（1000 ^℃）时损失严重。不同尺寸SiO₂制备多孔碳的元素分析,表明15 nm制备的氮硫含量更高,分别为3.24%和7.28%。（3）通过XPS测试,氮掺杂多孔碳的中吡啶氮（55.8%）和石墨氮（20%）含量较多。不同碳化温度所得氮硫双掺碳中,温度越高,吡啶氮减少,石墨氮含量增加;硫主要以噻吩硫的形式存在。（4）通过电化学测试CV和ORR,聚合物刷制备氮掺杂碳材料电化学性能优于物理混合,起始电势0.08 V,半波电势为-0.169 V,极限电流密度5.08mA/cm²。氧还原为四电子路径。耐久性测试表明良好的电化学稳定性,10000圈加速后,半波电势相左移动30 mV。不同碳化温度制备的氮硫双掺杂多孔碳中,900 ^℃制备多孔碳的电化学性能最好,起始电势达起始电势为0.03 V（vs.Hg/HgO）,且氧还原经历四电子过程。耐久性测试结果说明电化学稳定性。（5）通过不同纳米尺寸模板制备多孔碳的CV和ORR测试。15 nm SiO₂的氮硫双掺杂多孔碳的电化学性能更好。更多还原

【Abstract】 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.更多还原