Co基多级纳米线阵列的设计及其全分解水性能的研究

发布时间：2018-05-02 11:50

本文选题：Co基纳米线 + Ni/Fe-水滑石　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：近年来,由于环境污染的加重和传统化石燃料的短缺,人们越来越重视清洁能源的使用。在各种新能源中,与太阳能和风能相比,氢能具有便于储存、不受气象条件影响等优点。若实现氢能的大范围应用,可以在很大程度上缓解、解决化石燃料短缺和环境污染等难题。在各种制氢方法中,电解水制取氢气具有能量利用率高和操作简单等优点,是最有希望成为一种大范围应用的生产氢气的方法。但是,在实际生产过程中,需要使用到贵金属催化剂,由于其价格昂贵无法进行大规模生产。因此,制备一种可代替贵金属且价格低廉的高效催化剂,对于电解水制氢的工业化生产至关重要。过渡金属氧化物,由于具有良好的催化性能、低廉的价格被认为是贵金属氧化物催化剂的一种有效替代品。其中Co_3O_4和Ni/Fe-水滑石等催化剂,由于具有良好的催化性能、易于制备等优点已经被广泛研究。催化反应通常发生在催化剂的表面,因此催化剂的几何结构将会对催化性能产生较大的影响。通常,氧化物催化剂材料由于导电性差或催化剂比表面积较小等缺点,而影响催化性能的发挥。本文采用水热法,通过在还原气氛煅烧的方式分别制备导电性良好的Co_3O_(4-x)和Co纳米线阵列,最后将上述纳米线阵列与高催化活性的Ni/Fe-水滑石复合构建多级阵列电极,两种材料起到协同效应从而提高Co基催化剂的性能,多级结构可以最大程度的暴露催化剂的活性表面,增大活性位点与电解液的接触面积,从而提高催化效率。首先,通过水热法在不锈钢网上原位生长出Co基纳米线前驱体,将前驱体在空气中高温煅烧转化为Co_3O_4纳米线阵列,再经NaBH4处理在Co_3O_4引入氧空位,随后通过电沉积的方式,成功地在阵列表面生长Ni/Fe-水滑石纳米片,构建Co_3O_(4-x)@LDH多级结构。电化学测试结果表明,其在30 mA×cm-2电流密度下析氧过电位为272 m V,Tafel斜率为85.5 mV×dec-1;在10 mA×cm-2电流密度下析氢过电位为-284 mV,Tafel斜率为-72 m V×dec-1,催化性能均优于未处理的Co_3O_(4-x)纳米线阵列。随后,为了进一步提高催化剂导电性,将Co基纳米线前驱体在氢氩气氛下高温处理,制备金属Co纳米线阵列,金属Co纳米阵列具有更好的导电性。在Co纳米线表面电沉积Ni/Fe-水滑石纳米片,成功构建Co@LDH多级结构并测试其Co@LDH多级结构的全解水性能。结果表明,在30 m A×cm-2电流密度下析氧过电位为262 mV,Tafel斜率为39.8 m V×dec-1,析氢过电位为-265 mV,Tafel斜率为-65 mV×dec-1,在经过50000 s的反应后催化活性基本不变,展示出了良好的稳定性。
[Abstract]:In recent years, more and more attention has been paid to the use of clean energy due to the worsening of environmental pollution and the shortage of traditional fossil fuels. Compared with solar and wind energy, hydrogen energy has the advantages of convenient storage and no influence of meteorological conditions. If the hydrogen energy is widely used, it can alleviate the shortage of fossil fuels and solve the problems of environmental pollution to a great extent. Among the various hydrogen production methods, electrolytic water for hydrogen production has the advantages of high energy efficiency and simple operation, which is the most promising method for hydrogen production in a wide range of applications. However, in the actual production process, precious metal catalysts need to be used, because of their high prices can not be large-scale production. Therefore, it is very important for the industrial production of hydrogen by electrolytic water to prepare a high efficient catalyst which can replace precious metals. Transition metal oxides are considered as an effective substitute for noble metal oxide catalysts due to their good catalytic properties. Among them, Co_3O_4 and Ni / Fe- hydrotalcite catalysts have been widely studied because of their good catalytic performance and easy preparation. The catalytic reaction usually takes place on the surface of the catalyst, so the geometry of the catalyst will have a great influence on the catalytic performance. Usually, the performance of oxide catalysts is affected because of their poor conductivity or low specific surface area. In this paper, by hydrothermal method and calcination in the reduction atmosphere, we prepared CoSZ _ 3O _ (4-x) and Co nanowire arrays with good electrical conductivity respectively. Finally, the nanowire arrays were combined with Ni / Fe-hydrotalcite with high catalytic activity to form multistage array electrodes. The two kinds of materials play a synergistic effect so as to improve the performance of Co-based catalysts. The multilevel structure can maximize the exposure of the active surface of the catalyst and increase the contact area between the active sites and the electrolyte thus improving the catalytic efficiency. First of all, Co nanowire precursors were grown in situ on stainless steel by hydrothermal method. The precursors were calcined in air at high temperature to form Co_3O_4 nanowire arrays, then oxygen vacancies were introduced into Co_3O_4 by NaBH4 treatment, and then electrodeposited. The Ni / Fe-hydrotalcite nanocrystals were successfully grown on the surface of the array and the multilevel structure of Co_3O_(4-x)@LDH was constructed. The results of electrochemical measurement show that the overpotential of oxygen evolution is 272mV / cm-2 at 30 Ma 脳 cm-2 current density, the slope is 85.5 MV 脳 dec-1 and the overpotential of hydrogen evolution is -284mV / cm-2 Tafel slope of -72mV 脳 dec-1 at the current density of 10mA 脳 cm-2, which is superior to the untreated Co3OOt4-x nanowire array. Then, in order to further improve the conductivity of the catalyst, the Co nanowire precursor was treated in hydrogen argon atmosphere at high temperature to prepare the metal Co nanowire array, and the metal Co nanowire array had better electrical conductivity. Ni / Fe- hydrotalcite nanocrystals were electrodeposited on the surface of Co nanowires. The multistage structure of Co@LDH was successfully constructed and its Co@LDH multilevel structure was tested. The results show that the slope of oxygen evolution overpotential is 39.8 MV 脳 dec-1 at 30 Ma 脳 cm-2 current density, and the slope of hydrogen evolution overpotential is -65 MV 脳 dec-1 at 30 Ma 脳 cm-2 current density. After the reaction of 50000 s, the catalytic activity is almost unchanged, showing good stability.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;O643.36

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