【作者】 贾荣利；

【导师】 王成扬；

【作者基本信息】 天津大学 ， 化学工艺， 2005， 博士

【摘要】 直接甲醇燃料电池(DMFC)具有能量密度高、操作温度低等优点,尤其是使用液体燃料更能够降低DMFC系统装置的复杂性,因此被认为是便携式移动移动电源的首选。DMFC阳极主要是使用炭载铂或炭载铂合金作为电催化剂。但是,由于在阳极催化甲醇氧化脱H的过程会产生CO而吸附在催化剂的表面活性位上,从而降低了甲醇电氧化的速率。因此,制备高活性的阳极电催化剂是提高DMFC性能的关键因素之一。沥青基超细炭粉(PCSP)是在碳质中间相的成核和中间相小球体的形成过程中,从含有中间相球体的中间相沥青中分离中间相炭微球(MCMB)的同时获得了大量的粒径小于1.0μm的小的碳质颗粒,是碳质中间相球体形成和长大的构筑单元。除我们课题组外,还没有发现其它的关于对此类炭材料研究方面的相关报道。由于缺少对PCSP性质的深刻认识和实际应用方面的基础研究,MCMB工业化生产过程中生成了大量的PCSP副产品目前没有任何应用的价值。为了能够将PCSP加以有效利用、降低DMFC的成本、提高DMFC阳极电催化剂性能,本文采用石墨化沥青基超细炭粉(GPCSP)作为一种新型的Pt基电催化剂的载体进行了基础性研究,并期望GPCSP的特殊性质能够提高Pt基电催化剂的甲醇电氧化性能。首先利用KOH活化、HNO3氧化、空气氧化和高温N2处理等方式对GPCSP进行了前处理。KOH活化、HNO3氧化和空气氧化处理后,GPCSP的比表面积均有不同程度的增加,并且在GPCSP表面形成了一定数量的含氧官能团;高温N2处理后,GPCSP比表面积变化不大,石墨化程度得到增加,表面含氧官能团的数量明显降低。10 wt% Pt/GPCSP电催化剂的甲醇电氧化实验结果显示,未经过前处理的GPCSP为载体的Pt/S0电催化剂的活性比以Vulcan XC-72炭黑为载体的Pt/CB电催化剂的活性高出30 %,达到850 mA·mgPt-1。Pt/GPCSP电催化剂显示更高甲醇电氧化活性的原因是由于GPCSP载体具有特殊的性能,如高的导电性能和石墨化程度等。同时,载体的前处理对Pt/GPCSP电催化剂的的活性都有不同程度的影响,其中Pt/SKN系列电催化剂的活性最高。Pt/GPCSP电催化剂经过300℃处理后,活性稍微有些降低;而经过900℃处理后,活性降低一倍以上。10 wt(Pt+Ru)% Pt-Ru/GPCSP合金电催化剂中Pt:Ru原子比都接近85:15,Pt-Ru合金相中Ru的含量为1-2 %左右,大量的Ru是以非晶态Ru氧化物的形式存在。甲醇电氧化实验结果显示,Pt-Ru/S0合金电催化剂的活性比Pt-Ru/CB合金电催化剂高23 %,比Pt/S0电催化剂高110 %,达到1790 mA·mgPt-1。Pt-Ru/SKN系列电催化剂具有最高的活性。Pt-Ru/GPCSP合金电催化剂经过300℃处理后,活性有所增加;经过900℃处理后,活性明显降低。10 wt(Pt+Co)% Pt-Co/GPCSP合金电催化剂中Pt:Co原子比都接近80:20,Pt-Co合金相中Co的含量为3-4 %左右,大量的Co是以非晶态Co氧化物的形式存在。甲醇电氧化实验结果显示,Pt-Co/S0合金电催化剂的活性比Pt-Co/CB合金电催化剂高20 %,比Pt/S0电催化剂高136 %,达到2010 mA·mgPt-1。Pt-Co/SKN系列电催化剂具有最高的活性。Pt-Co/GPCSP合金电催化剂经过300℃处理后,活性有所增加;经过900℃处理后,活性明显降低。更多还原

【Abstract】 Direct methanol fuel cells (DMFC) are the most suitable for mobile and portable electronic applications because of their high energy density, relatively low operating temperature, and the convenience of a liquid fuel that, thereby, enables a greatly simplified system design. Carbon supported platinum is commonly used as the anode electrocatalyst. However, one of the problems is sluggish methanol oxidation kinetics at the anode, which is made worse by the progressive loss of catalytically active sites by CO-like reaction intermediates that are generated during the stepwise dehydrogenation of methanol. Therefore, the efforts to icrease the efficiency of DMFC still focused on improvement in the performance of anode electrocatalyts.Pitch-based carbon submicron-particles (PCSP) was small carbonanous particles with the size <1.0μm, and separated from mesocarbon mcirobeads (MCMB), which was obtained during the formation and development process of carbonaceous mesophase. PCSP was considered as the basic units of the formation and development of MCMB. However, a large amount of PCSP, which was the byproduct produced during the industrial manufacture of MCMB, is of no use for application due to lacking of profound knowledge of its properties and of the basic research of its application. In order to utilize PCSP effectively, reduce the cost of DMFC and improve the anode electrocatalyst performance, in this paper, exploratory researches were done by using the graphitic PCSP (GPCSP) as the novel supports for Pt-based electrocataysts, and it is expected for GPCSP supported Pt-based electrocatalysts to obtain high performance of methanol electro-oxidation.First, GPCSP was treated by KOH activation, HNO3 oxidation, air oxidation, and thermal treatment in N2 flow, respectively. After KOH activation, HNO3 and air oxidation, the specific surface area of GPCSP increased, and oxygen-contained groups were formed on the surface of GPCSP. After thermal treatment, the specific surface area of GPCSP changed slightly, and the amount of oxygen-contained groups decreased obviously.The analysis of methanol oxidation showed that the mass specific activity of 10 wt% Pt/S0 electrocatalyst was 850 mA·mgPt-1, with a 30 % increase than that of 10wt% Pt/CB electrocatalyst. This increase in the activity of methanol oxidation for Pt/GPCSP electrocatalysts was attributed to the characteristics of the support, such as the high conductivity and graphitized degree. The performance of the Pt/GPCSP electrocatalysts was affected by using the different pre-treated supports. Among the all electrocatalysts, the Pt/SKN electrocatalysts showed the most highly catalytic activity for the oxidation of methanol. The activity of Pt/GPCSP electrocatalysts decreased slightly after the thermal treatment in N2 flow at 300℃; and after thermal treatment at 900℃, its activity decreased obviously.The atomic compostions for 10 wt(Pt+Ru)% Pt-Ru/GPCSP electrocatalysts were nearly 85:15. But there was a large excess of unalloyed amorphous Ru oxide, with only about 1-2 % of the Ru alloyed with Pt. The analysis of methanol oxidation showed that the mass specific activity of Pt-Ru/S0 electrocatalyst was 1790 mA·mgPt-1, with a 23 % increase than that of Pt-Ru/CB electrocatalyst and a 110 % increase than that of Pt/S0 electrocatalyt. Among the all electrocatalysts, the Pt-Ru/SKN electrocatalysts showed the most highly catalytic activity for the oxidation of methanol. The activity of Pt-Ru/GPCSP electrocatalysts increased slightly after the thermal treatment at 300℃; while after thermal treatment at 900℃, its activity decreased obviously.The atomic compostions for 10 wt(Pt+Co)% Pt-Co/GPCSP electrocatalysts were nearly 80:20. But there was a large excess of unalloyed amorphous Co oxide, with only about 3-4 % of the Co alloyed with Pt. The analysis of methanol oxidation showed that the mass specific activity of Pt-Co/S0 electrocatalyst was 2010 mA·mgPt-1, with a 20 % increase than that of Pt-Co/CB electrocatalyst and a 136 % increase than that of Pt/S0 electrocatalyt. Among the all electrocatalysts, the Pt-Co/SKN electrocatalysts showed the most highly catalytic activity for the oxidation of methanol. The activity of Pt-Co/GPCSP electrocatalysts increased slightly after the thermal treatment at 300℃; while after thermal treatment at 900℃, its activity decreased obviously.更多还原