钯银钴和银钴金属合金纳米催化剂的合成及其电化学性能研究
发布时间：2018-10-14 19:13
【摘要】：由于化石燃料的过度消耗及自然资源匮乏等原因使得新能源及可持续能源的开发利用迫在眉睫。Li电池虽然现在占据市场较大的份额,但是仍有很多技术问题。燃料电池是一种只需定期充入燃料就可以将燃料的化学能直接转化为电能的装置,并能够不断地提供能量,且无污染,转化率高,是一种理想的能量转换方式。催化剂是燃料电池中最关键的一部分,主流催化剂中贵金属Pt和Pd的含量往往较高,这就导致电池的成本增加,这一问题极大的限制了燃料电池的发展及应用。因此,本着催化剂具有低成本高催化性能的研究目标,本文通过有机合成制备出具有成本低电催化性能好的金属合金纳米催化剂AgCo和Co掺杂的PdAgCo。我们首先通过电化学工作站进行循环伏安扫描(CV),然后对PdAgCo和AgCo分别进行直接甲酸氧化测试(FAO),氧还原测试(ORR)以及稳定性测试,并通过透射电镜(TEM),高倍电镜(HRTEM),X射线衍射(XRD)对催化剂的形貌、结构、物相及组成进行了表征和分析。(1)本文通过固定加入反应体系的表面还原剂(油胺OA)的量,分别合成了单分散的Pd AgCo和Pd Ag纳米颗粒,透射电镜下可以看到,PdAg合金纳米催化剂是直径为6 nm左右的颗粒,大小比较均一,Co掺杂的PdAgCo是粒径为8 nm左右的纳米球体,粒径也相对比较均一。XRD数据显示,在PdAg纳米颗粒主要以111面的PdAg合金的形式存在的,在PdAgCo/C纳米颗粒中尽管只有少量的Co元素掺杂进去,也形成了三金属的合金纳米颗粒。电化学测试结果表明PdAgCo/C(1 133.249 mAmgPd-1)的甲酸氧化催化性能是商业Pd/C(483.563 mAmgPd-1])的2.4倍以及双金属PdAg/C(680.741 mAmgPd-1)的1.7倍,即少量Co元素的掺杂对双金属PdAg的甲酸氧化性能也有较大的提高。此实验中的油胺是一种长链有机还原剂,除了能够控制颗粒形貌外,还起到封端剂的作用。(2)通过简单的操作步骤,在有机液相中还原制备了一系列不同煅烧温度的AgCo和不同负载载体的AgCo,来比较其电催化性能。透射电镜(TEM)显示部分AgCo纳米颗粒为8nm左右的类球形颗粒,而部分AgCo纳米颗粒则发生了融合。XRD数据确认了所制备材料部分为fcc结构的AgCo合金。电化学测试表明:金属Ag和Co发生融合的最佳煅烧温度是550℃,在此温度条件下将活性炭载体更换为ZIF-8,可得到AgCo/ZIF-8-550℃纳米颗粒,该颗粒的电化学活性优于AgCo/C-550℃纳米颗粒的。(3)结合理论计算的指导,我们还通过控制不同的煅烧啊烧升温速度,来获得最佳催化性能的AgCo催化剂,即分别以5℃/min、8℃/min和10℃/min煅烧AgCo/ZIF-8纳米催化剂至550℃。电化学测试表明,合成的AgCo/ZIF-8-550℃在煅烧速度为8℃/min州其具有比较好的氧还原(ORR)活性和稳定性。
[Abstract]:Because of the excessive consumption of fossil fuels and the shortage of natural resources, it is urgent to develop and utilize new and sustainable energy. Although Li batteries now occupy a large market share, there are still many technical problems. Fuel cell is a kind of device which can directly convert the chemical energy of fuel into electric energy by filling fuel periodically, and it can provide energy continuously, without pollution and high conversion rate, so it is an ideal energy conversion mode. Catalyst is the most important part of fuel cell. The content of noble metal Pt and Pd in the mainstream catalyst is often higher, which leads to the increase of the cost of fuel cell. This problem greatly limits the development and application of fuel cell. Therefore, in line with the research goal of low cost and high catalytic performance of catalysts, metal alloy nano-catalysts AgCo and PdAgCo. doped with Co were prepared by organic synthesis. We first performed cyclic voltammetry scanning (CV), on an electrochemical workstation and then performed direct formic acid oxidation test (FAO), oxygen reduction test (ORR) and stability test on PdAgCo and AgCo respectively. The morphology, structure, phase and composition of the catalyst were characterized and analyzed by transmission electron microscope (TEM),) high power electron microscope (HRTEM), X ray diffraction (XRD). (1) the amount of surface reductant (oleamine OA) was fixed in the reaction system. Monodisperse Pd AgCo and Pd Ag nanocrystals were synthesized respectively. The results of transmission electron microscopy showed that the PdAg alloy nanocrystalline catalyst was about 6 nm in diameter and uniform in size, and Co doped PdAgCo was a nano-sphere with a diameter of about 8 nm. XRD data show that PdAg nanoparticles mainly exist in the form of 111-plane PdAg alloy, and in PdAgCo/C nanoparticles, even though only a small amount of Co elements are doped in them, tri-metal alloy nanoparticles are formed. The results of electrochemical measurement show that the catalytic performance of PdAgCo/C (1 133.249 mAmgPd-1) for formic acid oxidation is 2. 4 times of that for commercial Pd/C (483.563 mAmgPd-1) and 1. 7 times for bimetallic PdAg/C (680.741 mAmgPd-1). The oleamine in this experiment is a kind of long chain organic reductant, which can not only control the morphology of particles, but also act as an entrapment agent. (2) through simple operation steps, A series of AgCo calcined at different temperatures and AgCo, supported on different supports were prepared by reduction in organic liquid phase to compare their electrocatalytic properties. Transmission electron microscopy (TEM) showed that some AgCo nanoparticles were spherical particles about 8nm, while some AgCo nanoparticles were fused. XRD data confirmed that some of the prepared AgCo nanoparticles were AgCo alloys with fcc structure. The electrochemical test showed that the optimal calcination temperature for fusion of metal Ag and Co was 550 鈩，
本文编号：2271381
[Abstract]:Because of the excessive consumption of fossil fuels and the shortage of natural resources, it is urgent to develop and utilize new and sustainable energy. Although Li batteries now occupy a large market share, there are still many technical problems. Fuel cell is a kind of device which can directly convert the chemical energy of fuel into electric energy by filling fuel periodically, and it can provide energy continuously, without pollution and high conversion rate, so it is an ideal energy conversion mode. Catalyst is the most important part of fuel cell. The content of noble metal Pt and Pd in the mainstream catalyst is often higher, which leads to the increase of the cost of fuel cell. This problem greatly limits the development and application of fuel cell. Therefore, in line with the research goal of low cost and high catalytic performance of catalysts, metal alloy nano-catalysts AgCo and PdAgCo. doped with Co were prepared by organic synthesis. We first performed cyclic voltammetry scanning (CV), on an electrochemical workstation and then performed direct formic acid oxidation test (FAO), oxygen reduction test (ORR) and stability test on PdAgCo and AgCo respectively. The morphology, structure, phase and composition of the catalyst were characterized and analyzed by transmission electron microscope (TEM),) high power electron microscope (HRTEM), X ray diffraction (XRD). (1) the amount of surface reductant (oleamine OA) was fixed in the reaction system. Monodisperse Pd AgCo and Pd Ag nanocrystals were synthesized respectively. The results of transmission electron microscopy showed that the PdAg alloy nanocrystalline catalyst was about 6 nm in diameter and uniform in size, and Co doped PdAgCo was a nano-sphere with a diameter of about 8 nm. XRD data show that PdAg nanoparticles mainly exist in the form of 111-plane PdAg alloy, and in PdAgCo/C nanoparticles, even though only a small amount of Co elements are doped in them, tri-metal alloy nanoparticles are formed. The results of electrochemical measurement show that the catalytic performance of PdAgCo/C (1 133.249 mAmgPd-1) for formic acid oxidation is 2. 4 times of that for commercial Pd/C (483.563 mAmgPd-1) and 1. 7 times for bimetallic PdAg/C (680.741 mAmgPd-1). The oleamine in this experiment is a kind of long chain organic reductant, which can not only control the morphology of particles, but also act as an entrapment agent. (2) through simple operation steps, A series of AgCo calcined at different temperatures and AgCo, supported on different supports were prepared by reduction in organic liquid phase to compare their electrocatalytic properties. Transmission electron microscopy (TEM) showed that some AgCo nanoparticles were spherical particles about 8nm, while some AgCo nanoparticles were fused. XRD data confirmed that some of the prepared AgCo nanoparticles were AgCo alloys with fcc structure. The electrochemical test showed that the optimal calcination temperature for fusion of metal Ag and Co was 550 鈩，
本文编号：2271381
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