Mo2C/MWCNT催化剂制备及其电催化氧化甲醇性能

Preparation of Mo2C/MWCNT catalysts and its performance in electrocatalytic oxidation of methanol

  • 摘要: 随着经济的快速发展,化石燃料需求量的逐年增加以及环保问题的日益突出,能源问题显然已成为焦点问题。亟需加快能源结构转型、提高能源利用率以及开发绿色新能源技术。同时国家也对新能源表现出极高的关注度,大力支持发展新能源产业。直接甲醇燃料电池是一种新型的能量转换装置,可以直接把化学能转化为电能,因其不受卡诺循环限制、能量密度高,清洁环保等优点引起研究者的广泛关注。直接甲醇燃料电池的阳极催化剂是其最关键的组成部分,其催化性能的优劣直接影响电池的性能。目前的商业催化剂主要为贵金属,昂贵的价格、复杂的制备过程以及易受中间体毒化等问题严重制约其商业化。Mo的碳化物由于其独特的d带电子结构,表现出与贵金属类似的催化活性。分别将MoO2、MoO3和Mo2C负载于多壁碳纳米管时,Mo2C负载于多壁碳纳米管的催化剂甲醇电氧化活性最高。为探究载体表面活性位点对甲醇电催化氧化的影响,以不同质量比的钼酸铵和多壁碳纳米管为前驱体,制备了具有一维纳米结构的Mo2C/MWCNT催化剂,并评价其电催化氧化甲醇性能。利用X射线衍射仪、扫描电镜、透射电镜等测试手段对催化剂形貌及结构进行分析。结果显示,0.7 V(vs. Hg/HgO)电压时,前驱体钼酸铵和MWCNT的质量比为1∶1时(Mo2C/MWCNT−1)催化剂的甲醇电催化氧化性能最佳,其电流密度为185 mA/cm2,且10 h后仍保留了初始催化活性的76.19%。此时Mo2C均匀分散在多壁碳纳米管管壁,粒径约3~12 nm。另外,较小的电荷转移电阻有利于甲醇电催化氧化性能的提高。

     

    Abstract: With the rapid economic development, the increasing demand for fossil fuels and the growing importance of environmental issues, the energy issue has clearly become a focal point. There is an urgent need to speed up the transformation of the energy structure, improve energy utilization and develop new green energy technologies. At the same time, the government also pays great attention to new energy and strongly supports the development of the new energy industry. Direct methanol fuel cell is a new type of energy conversion device that can directly convert chemical energy into electric energy, and has attracted great attention from researchers due to its advantages of not being limited by the Carnot cycle, high energy density, cleanliness and environmental protection. The anode catalyst of direct methanol fuel cell is the most critical component, and its catalytic performance directly affects the performance of the cell. The current commercial catalysts are mainly made of precious metals, and their commercialization is severely restricted by the high price, complicated preparation process, and susceptibility to intermediate poisoning. Carbides of Mo exhibit catalytic activities similar to those of noble metals due to their unique d-band electronic structures. In this study, the MoO2, MoO3 and Mo2C were loaded on multi-walled carbon nanotubes, respectively, the highest methanol electrooxidation activity was observed for the catalysts with Mo2C loaded on multi-walled carbon nanotubes. To study the effect of carrier surface sites on the electrocatalytic oxidation of methanol, the electrocatalytic oxidation performance of methanol was evaluated by using the Mo2C/MWCNT catalysts with one-dimensional nanostructures, which were prepared by using ammonium molybdate and multi-walled carbon nanotubes with different mass ratios as precursors. The X-ray diffractometer, scanning electron microscope, and transmission electron microscope were utilized to analyze the morphology and structure of the catalysts. The results showed that the best methanol electrocatalytic oxidation performance of the catalyst was achieved at 0.7 V (vs. Hg/HgO) with the mass ratio of precursor ammonium molybdate and MWCNT of 1:1 (Mo2C/MWCNT-1), and the current density was 185 mA/cm. The current density retained 76.19% of the initial catalytic activity after 10 h. The Mo2C was homogeneously dispersed in the walls of the multi-walled carbon nanotubes with the particle sizes of about 3~12 nm. In addition, the smaller charge transfer resistance was favorable to the methanol electrocatalytic oxidation performance.

     

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