镍基非贵金属催化剂的制备及电催化水分解性质研究

发布时间：2018-03-19 19:17

本文选题：镍基材料　切入点：电沉积　出处：《中国科学技术大学》2015年硕士论文　论文类型：学位论文

【摘要】：电催化或光催化水分解制氢,是解决能源危机和环境污染的有效途径之一。贵金属催化剂具有较高的催化水分解的活性,但是由于贵金属低储量、高成本的特点,限制了其大规模应用。因此,寻找有效的非贵金属材料催化剂变得尤为重要。近年来,人们一直在尝试改进非贵金属催化剂的催化性能,包括：降低催化水分解的过电势、提高催化活性、提高能量转换效率、提高稳定性等。本文通过两种途径来提高镍基材料的催化性能：(1).通过电沉积法,将镍基材料生长在碳纳米管修饰电极上,用于催化水分解。(2).合成双金属氧化物NiCo2O4纳米线,对其催化水氧化的性能进行分析。在阳极电势下,在含有镍离子的硼酸钾(KBi)缓冲溶液中,镍基材料通过电沉积生长到了MWCNTs/ITO上。电化学测试显示NiOx-MWCNTs电催化剂材料具有很好的催化活性和较低的过电势(-200mV)。 NiOX催化剂材料通过扫描电子显微镜(SEM)、 X射线能量散射谱(EDX)和X射线光电子能谱(XPS)测试进行了进一步的表征。在含有镍离子的KBi溶液中,在还原电势下(-1.2V vs. Ag/AgCl),电沉积到MWCNTs上的镍基薄膜能够有效的用于产氧反应(OER)和产氢反应(HER)。在还原状态下,H2-NiOx-MWCNTs催化剂薄膜能够在低过电势下有效地催化产氢反应。当转换为氧化条件时(+1.1V vs. Ag/AgCl), MWCNTs上的无定形H2-NiOx薄膜转换成了另一种无定形材料(O2-NiOx),能够有效地用于水氧化反应。NiOx-MWCNTs催化剂通过SEM,透射电子显微镜(TEM), EDX和XPS进行了表征。结果显示O2-NiOx-MWCNTs薄膜的O含量高于H2-NiOx-MWCNTs薄膜的O含量。NiOx-MWCNTs具有良好的稳定性,当电势在还原状态和氧化状态之间转换时,薄膜的催化性能能够既催化水还原产氢又催化水氧化产氧。此外,我们利用简单的两步法,合成了NiCo2O4纳米线阵歹(NWAs)。NiCo2O4NWAs催化剂作为工作电极催化水氧化时,表现出了很高的活性和良好的稳定性。在同样条件下,NiCo2O4NWAs的电流密度甚至高于纳米Ir02催化剂的电流密度。利用球差显微镜TEM对NiCo2O4纳米线进行了原子层面的分析,发现NiCo2O4纳米线中存在高指数活性面及大量的表面原子台阶,这可能是NiCo2O4纳米线催化剂具有低过电势和高催化活性的主要原因。该体系中的法拉第效率大于95%。
[Abstract]:Electrocatalysis or photocatalytic water decomposition to produce hydrogen is one of the effective ways to solve the energy crisis and environmental pollution. Precious metal catalysts have high catalytic activity for water decomposition, but due to the low storage and high cost of precious metals, Therefore, it is very important to find effective catalysts for non-precious metal materials. In recent years, people have been trying to improve the catalytic performance of non-noble metal catalysts, including reducing the overpotential of catalytic water decomposition, improving catalytic activity and energy conversion efficiency. In this paper, the catalytic performance of nickel-based materials was improved by means of two ways. Nickel based materials were grown on carbon nanotube modified electrodes by electrodeposition, which were used to catalyze water decomposition. NiCo2O4 nanowires were synthesized. The catalytic performance of water oxidation was analyzed. At anodic potential, in potassium borate buffer solution containing nickel ion, Nickel based materials were grown on MWCNTs/ITO by electrodeposition. Electrochemical tests showed that NiOx-MWCNTs electrocatalysts had good catalytic activity and lower overpotential (~ 200mV). NiOX catalyst materials were characterized by scanning electron microscopy (SEM) and X-ray energy scattering. The spectra were characterized by EDX) and X-ray photoelectron spectroscopy (XPS). In KBi solution containing nickel ion, The nickel based films deposited on MWCNTs can be effectively used for oxygen production and hydrogen production under the reduction potential of 1.2V vs. AgClN. In the reduced state, the H2-NiOx-MCNTs catalyst films can effectively catalyze the hydrogen production reaction at low over-potential. The amorphous H2-NiOx film on MWCNTs was converted into another amorphous material, O _ 2-NiOxO _ (2), which can be effectively used in water oxidation reaction. NiOx-MWCNTs catalyst was characterized by SEM, TEM, TEM, EDX and XPS when the oxidation conditions were changed to (1.1 V vs. AgCl _ (1)). The O content of O2-NiOx-MWCNTs film is higher than that of H2-NiOx-MWCNTs film. When the potential changes between the reduction state and the oxidation state, the catalytic performance of the film can not only catalyze the water to produce hydrogen, but also to oxidize the oxygen of the water. In addition, NiCo2O4 nanowire array catalyst NWAs.NiCo2O4NWAs was synthesized by a simple two-step method as a working electrode to catalyze water oxidation. Under the same conditions, the current density of NiCo2O4NWAs is even higher than that of nanocrystalline Ir02 catalysts. The atomic analysis of NiCo2O4 nanowires was carried out by spherical differential microscope (TEM). It is found that there are high exponent active surfaces and a large number of surface atomic steps in NiCo2O4 nanowires, which may be the main reasons for the low overpotential and high catalytic activity of NiCo2O4 nanowire catalysts. The Faraday efficiency in the system is greater than 95%.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O614.813;TQ116.2

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