新型碳基材料载铂电催化甲醇氧化性能研究
发布时间：2018-08-29 16:52
【摘要】：随着全球化石燃料的枯竭和环境污染问题日益严重,人们极力寻找一种新的能源来取代之。直接甲醇燃料电池(DMFCs)拥有极好的能量转化率且对环境无污染,受到了人们广泛的关注。直接甲醇燃料电池主要使用贵金属Pt为催化剂,但Pt面临着全球储量稀少和价格高等问题,制约了直接甲醇燃料电池的大规模应用。近年来,研究者开始把催化剂载体和助剂作为研究重点,来降低贵金属的使用量。其中多孔碳、碳化物和异质原子掺杂是研究的热点。在本论文中,我们使用多孔石墨(烯)半球、埃米尺度碳化钒和竹状氮掺杂碳化钨作为催化剂载体,来提高Pt的利用率以及Pt与载体结合的稳定性,从而达到同时提高电催化甲醇氧化反应活性和稳定性的目的。1、利用实心核多孔壳二氧化硅小球(SCMSSs)为模版,葡萄糖为碳源,氯化镍为石墨化催化剂,经1000℃加热、除模板和除杂质,制得了碗状多孔石墨(半球)(GLBs);同时与未石墨化的多孔碳(BLCs)进行比较。以它们为载体制备了Pt/GLB和Pt/BLC催化剂。物理表征结果表明,这种GLBs的直径和SCMSSs的直径一致,即前者完美的反向复制了SCMSSs的形貌,形成了多孔结构和较大的比表面积,促进了Pt颗粒的均匀分散且降低了Pt的粒径。电化学测试表明,Pt/GLB催化甲醇氧化的峰电流密度(2075 mA mg_(Pt)~(-1))是商业Pt/C(723mA mg_(Pt)~(-1))的2.87倍,是Pt/BLC(1846 mA mg_(Pt)~(-1))的1.12倍,且Pt/GLB具有显著提高的稳定性和抗毒化性能。2、通过调节钒酸钠和离子交换树脂的配比制得了不同形貌的碳-碳化钒(C-V_8C_7)复合材料。物理表征结果表明,随着钒酸钠用量增加,碳化钒从平均宽度为0.8 nm的棒状转变为粒径为10 nm左右的颗粒状,且团聚现象愈加明显。在这些碳化钒材料上负载Pt制得相应的Pt/C-V_8C_7催化剂。电化学测试结果显示,棒状Pt/C-V_8C_7(1605 mA mg_(Pt)~(-1))催化甲醇氧化的峰电流密度是颗粒状Pt/C-V_8C_7(1377 mA mg_(Pt)~(-1))的1.78倍,是商业Pt/C(775 mA mg_(Pt)~(-1))的2.07倍。更有意义的是,在0.4 V时,棒状Pt/C-V_8C_7催化甲醇氧化的电流密度是Pt/C的9倍,表明前者在低电位下具有更高的优势。另外,两个Pt/C-V_8C_7均比商业Pt/C具有更高的催化甲醇氧化的稳定性。分析认为,碳化物和贵金属之间存在的电子转移,改变了Pt的表面电子结构,提高了Pt和载体间的作用力,从而能够同时提高Pt/C-V_8C_7电催化活性和稳定性。3、使用三聚氰胺作为氮源和碳源,偏钨酸铵为钨源,制备了N掺杂的碳化钨(NWC-1);另外,在制备过程中添加FeCl_3改变材料性质,制得NWC-2;Fe的存在还能够提高材料的石墨化度。以它们为载体载Pt制得Pt/NWC-1和Pt/NWC-2催化剂,两者Pt颗粒的尺寸均约为1.0 nm;但FeCl_3的存在使得NWC-2的形貌的更加均一,Pt在其表面的分散也相应的更加均匀。电化学测试表明,Pt/NWC-2具有比Pt/NWC-1更高的催化甲醇氧化活性和稳定性,以及更好的导电性;这归因于NWC-2具有较高的石墨度和较均一的结构。
[Abstract]:With the depletion of fossil fuels and environmental pollution in the world, people are looking for a new energy to replace it. Direct methanol fuel cell (DMFCs) has attracted much attention for its excellent energy conversion and no pollution to the environment. Noble metal Pt is mainly used as catalyst for direct methanol fuel cell (DMFC). However, Pt is faced with the problems of scarcity of global reserves and high price, which restricts the large-scale application of DMFC. In recent years, researchers began to focus on catalyst carriers and auxiliaries to reduce the use of precious metals. Among them, porous carbon, carbides and heteroatoms doping are the focus of research. In this thesis, porous graphite (ene) hemispheres, Emmy scale vanadium carbide and bamboo nitrogen doped tungsten carbide were used as catalyst supports to improve the utilization of Pt and the stability of Pt binding to the support. In order to improve the activity and stability of methanol oxidation by electrocatalysis simultaneously, the solid core porous shell silica pellet (SCMSSs) was used as template, glucose as carbon source, nickel chloride as graphitization catalyst, and heated at 1000 鈩，
本文编号：2211818
[Abstract]:With the depletion of fossil fuels and environmental pollution in the world, people are looking for a new energy to replace it. Direct methanol fuel cell (DMFCs) has attracted much attention for its excellent energy conversion and no pollution to the environment. Noble metal Pt is mainly used as catalyst for direct methanol fuel cell (DMFC). However, Pt is faced with the problems of scarcity of global reserves and high price, which restricts the large-scale application of DMFC. In recent years, researchers began to focus on catalyst carriers and auxiliaries to reduce the use of precious metals. Among them, porous carbon, carbides and heteroatoms doping are the focus of research. In this thesis, porous graphite (ene) hemispheres, Emmy scale vanadium carbide and bamboo nitrogen doped tungsten carbide were used as catalyst supports to improve the utilization of Pt and the stability of Pt binding to the support. In order to improve the activity and stability of methanol oxidation by electrocatalysis simultaneously, the solid core porous shell silica pellet (SCMSSs) was used as template, glucose as carbon source, nickel chloride as graphitization catalyst, and heated at 1000 鈩，
本文编号：2211818
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