镍铁氢氧化物及其复合材料的析氧催化性能研究

发布时间：2018-05-27 03:43

本文选题：层状双金属氢氧化物 + OER　；参考：《安徽师范大学》2017年硕士论文

【摘要】：析氧反应(OER)作为水分解和可充电电池的一个重要反应,引起人们更加关注清洁能源的高效存能。优化OER催化剂的常见的方法是寻找新型的催化材料以及优化原有材料的化学成分和结构。然而,水分解的能量效率不高主要是由于OER反应的动力学缓慢。因此,我们急需寻找一种能够降低过电位以及加速OER反应的高效稳定的催化剂。最先作为OER催化剂的是贵金属材料,如RuO2等。但是其价格昂贵限制了应用。因此,我们将需要寻找一种矿产资源丰富、催化效率高的催化剂,这仍将是未来一段时间我们所将面临的挑战。以镍/铁为基础的化合物自上个世纪以来就作为高效的析氧催化剂。它们是最有前途的催化物质之一,以非贵金属为基础的催化剂显现出了比较高催化活性,甚至可能赶超贵金属等材料。本篇论文以镍铁氢氧化物及复合材料为对象,为大家提供了一种简单的方法。同时对镍铁双金属氢氧化物及其复合材料进行形貌、组成进行表征,并对其能够用作析氧电极催化剂进行电化学性能讨论,主要内容如下:1、优化了双金属氢氧化物纳米片的合成策略,以硝酸铁/镍溶液为原料,直接使用硼氢化钠进行还原得到纳米铁/镍金属单质,纳米粒子在水溶液中进一步反应,迅速得到目标产物镍铁-LDH。同时,这种方法可以通过调控母液中金属的比例,从而获得不同铁/镍比例的双金属氢氧化物。此外,由于Fe元素对材料的掺杂,使得制备的铁/镍双金属纳米片在电化学性能有一定的提升。在所有比例中,当Ni、Fe比例为6:4时,电流密度为20mA/cm2时过电位为0.24V。2、我们提出了一种可以迅速地制备大量NiFe-LDH/碳纳米管复合材料的方法。以碳纳米管为基底,调控CNTs与母液的相对浓度,使LDH能够均匀地生长在基底上,这不仅LDH纳米片的形状得到规整,还提高了稳定性,相比于单一的NiFe-LDH片状材料,其稳定性能够成倍增长。与传统的合成路线相比较,该方法简单高效且产量大,为产品的量产化提供了一定的参考价值。3、在前文中合成铁/镍-LDH的实验基础上,采用同样地制备方法制备了FeCoNi三元纳米材料。这种合成方法不仅条件温和、环境友好,同样在合成三元氢氧化物纳米片时也能很好地调控金属比例,这种方法也为合成其他单元或多元过渡金属氢氧化物提供了一定的依据,具有一定的普适性。同时,在不同比例的三元金属氢氧化物中,当Fe、Co、Ni比例为4:4:2时,其催化性能在这组材料中达到最优,电流密度值为10mA/cm2时过电位数值为0.273V,当电流密度值为20mA/cm2时过电位为0.282V。
[Abstract]:As an important reaction of water decomposition and rechargeable batteries, oxygen evolution reaction (Oer) has attracted more attention to the efficient energy storage of clean energy. The common way to optimize OER catalyst is to find new catalytic materials and optimize the chemical composition and structure of the original materials. However, the low energy efficiency of water decomposition is mainly due to the slow kinetics of OER reaction. Therefore, we urgently need to find an efficient and stable catalyst that can reduce overpotential and accelerate OER reaction. Precious metal materials such as RuO2 are the first catalysts for OER. But its high price limits its application. Therefore, we will need to find a catalyst with rich mineral resources and high catalytic efficiency, which will remain a challenge for us for some time to come. Nickel / iron based compounds have been used as efficient catalysts for oxygen evolution since the last century. They are one of the most promising catalysts. Catalysts based on non-precious metals show high catalytic activity and may even catch up with precious metals and other materials. In this paper, nickel-iron hydroxide and composite materials as the object, provide a simple method for everyone. At the same time, the morphology and composition of Ni-Fe bimetallic hydroxide and its composites were characterized, and the electrochemical properties of Ni-Fe bimetallic hydroxides as oxygen evolution electrode catalysts were discussed. The main contents are as follows: 1. The synthesis strategy of bimetallic hydroxide nanocrystals was optimized. Using ferric nitrate / nickel solution as raw material, sodium borohydride was directly used to reduce the nanocrystalline iron / nickel metal, and the nanoparticles reacted further in aqueous solution. The target product, Ni-Fe LDH, was obtained rapidly. At the same time, bimetallic hydroxides with different Fe / Ni ratios can be obtained by adjusting the proportion of metal in mother liquor. In addition, due to the doping of Fe to the material, the electrochemical properties of the prepared Fe / Ni bimetallic nanocrystals were improved to a certain extent. In all proportion, when the nio Fe ratio is 6:4, the overpotential is 0.24 V. 2 when the current density is 20mA/cm2, we propose a method to fabricate a large number of NiFe-LDH/ carbon nanotube composites rapidly. With carbon nanotubes as the substrate, the relative concentration of CNTs and mother liquor is regulated, so that LDH can grow on the substrate uniformly. This not only improves the shape of LDH nanoparticles, but also improves the stability, compared with the single NiFe-LDH sheet material. Its stability can multiply. Compared with the traditional synthetic route, this method is simple and efficient, and has a large yield, which provides a certain reference value for the mass production of the product. On the basis of the experiment of synthesizing Fe / Ni LDH in the previous paper, FeCoNi ternary nanomaterials were prepared by the same method. This synthetic method not only has mild conditions and is environmentally friendly, but also can control the proportion of metal well in the synthesis of ternary hydroxide nanocrystals. This method also provides a basis for the synthesis of other units or multielement transition metal hydroxides. It has certain universality. At the same time, in the different proportion of ternary metal hydroxides, when the ratio of Fe and Ni is 4:4:2, the catalytic performance is optimal in this group of materials. The overpotential value is 0.273V when the current density is 10mA/cm2, and 0.282V when the current density is 20mA/cm2.
【学位授予单位】：安徽师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TB33

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