【作者】 陈旭光；

【导师】 贺高红； 邵志刚；

【作者基本信息】 大连理工大学 ， 化学工程， 2009， 硕士

【摘要】 催化剂是质子交换膜燃料电池（PEMFC）最为重要的关键材料之一。目前,Pt/C是应用最为广泛的PEMFC催化剂,但是其仍面临着氧还原活性不高,稳定性较差,及成本过高等问题,限制了PEMFC整体的效率及商业化推广。本文首先确定了催化剂的制备方法并对Pt/C催化剂的制备进行了逐步放大,用以满足实验室对Pt基催化剂用量上的需求;后从引入助催化剂及新型载体两个方面出发,根据Pt与Ti同为d区元素的特点,尝试找到可以提升Pt基催化剂活性及稳定性的Ti系材料。首先,确定了催化剂的制备方法并对Pt/C催化剂的制备进行了逐步放大。对比了连续微波法（CM）、脉冲微波法（PM）及乙二醇回流法（EG-Reflux）所制备的Pt/C催化剂的电化学活性面积及Pt颗粒形貌,并比较了以不同C材料为载体的催化剂活性和结构,优选出制备方法（PM、EG-Reflux）及载体;对50%Pt担载量的Pt/C催化剂的制备进行了逐步放大,所得催化剂与商业化的Pt/C相比,电化学活性面积较大且颗粒较小;并且催化剂制备工艺稳定可靠。将自制催化剂制得电极,经过单池性能测试,催化剂可以满足使用要求。其次,制备了N及Sn掺杂的TiO₂（NTT）助催化剂,并利用X射线衍射（XRD）、透射电镜（TEM）、及X射线光电子能谱（XPS）等手段,对其晶形、形貌及元素组成进行了分析;以不同比例混入Pt/C催化剂后,对NTT/Pt/C共混催化剂进行了循环伏安动电位扫描和旋转圆盘电极测试,研究了其对Pt/C催化剂电化学活性面积及氧还原半波电位的影响;并在不同增湿条件下,在单电池中对NTT/Pt/C及Pt/C催化剂进行了测试。结果显示,NTT不仅可以促进Pt/C催化剂活性,并且其具有一定的保水能力,在低增湿工况下可以显著提升PEMFC的性能。最后,系统地研究了TiC及TiN作为Pt基催化剂载体的可能性。采用XRD、TEM以及比表面积及孔分布表征,对载体的晶形、形貌、比表面积及孔结构进行了分析;并采用动电位扫描法,研究了这两种载体的本征电化学稳定性。后以两种材料为载体,制备了不同Pt担载量的Pt/TiC、Pt/TiN催化剂,采用循环伏安法及旋转圆盘电极法测定了催化剂的电化学活性面积及氧还原活性;利用动电位扫描法及阶段电位氧化法评价了催化剂的电化学稳定性。结果表明,TiN及TiC及Vulcan XC-72碳粉三种材料相比,TiC与Vulcan XC-72碳粉材料电化学稳定性相当,皆优于TiN材料;担负Pt后,Pt/TiN与Pt/C催化剂氧还原活性相当,且优于Pt/TiC催化剂。更多还原

【Abstract】 The catalyst is one of the most significant key materials for Proton Exchange Membrane Fuel Cells（PEMFCs）.Presently,the Pt/C plays as the most widely used catalyst for PEMFCs, however,it also possesses several problems,such as high cost,low activity of oxygen reduction reaction（ORR） and stability,which stock the the efficiency and commercializing of PEMFCs. In this thesis,fisrtly,the methods for preparing catalyst were confirmed and the yield of Pt/C was step wisely scaled up,in order to meet the consumation of Pt-based catalyst at laboratory.Then focusing on the co-catalyst and novel support,some promising materials were studied aiming for improving Pt-based catalyst’s activity and stability.Firstly,the methods for preparing catalyst were confirmed and the yield of Pt/C was step wisely scaled up.Though comparing the activity and form of Pt/C,the optimum method and support were selected within different preparing methods（constant microwave,pulse microwave and EG refluxing） and carbon materials.The Pt/C with 50%Pt loading was prepared with stepwise yield target.Compared with the commercial Pt/C,the homemade catalyst showed smaller Pt particle size and bigger ECA.The quality of homemade catalyst was stable within repeated preparation.Moreover,it can be found from single cell test that the homemade catalyst is a promising catalyst for PEMFCs.Secondly,the N and Sn doped TiO₂（NTT） was prepared and characterized by XPS,TEM and XRD.The NTT/Pt/C catalyst,constituted by different contents of NTT,were tested by the cyclic voltammetry（CV） and the rotating disk electrode（RDE） method for investigating their electrochemically active surface area as well as their half-wave potential of ORR.The NTT/Pt/C catalysts were also tested within single cells with H₂/O₂ and H₂/Air under different humidity.The results indicated that through the addition of NTT,besides the activity of Pt/C could be improved,the performance of PEMFC under low humidity was also highly promoted mainly due to the water retention characteristic of NTT.Thirdly,TiC and TiN were systematically investigated to apply as the supports of Pt-based catalyst.The supports were characterized by XRD,TEM,BET to analyze their crystal form, profile,specific surface area and pore structure.The electrochemical stabilities of supports were tested by dynamic potential scanning.The Pt/TiC and Pt/TiN with various Pt loading were synthesized and tested by CV and RDE for investigating their electrochemical area（ECA） and activity of ORR;moreover their electrochemical stabilities were also tested by dynamic potential scanning and stepwise potential oxidation.The results indicated that within three kinds of mterials,the electrochemical stability of Vulcan XC-72 carbon particles could be commensurate with TiC,which excelled the TiN material.After Pt being loaded,the Pt/TiN and Pt/C possessed comparative activities for ORR and performed better than Pt/TiC.更多还原