镍基层状金属氢氧化物电催化剂的结构与性能调控研究

发布时间：2018-06-28 15:28

本文选题：水分解 + 电化学　；参考：《中国科学技术大学》2017年硕士论文

【摘要】：电催化水解被认为是可持续与可再生能源转移和储存的一个重要的途径。然而,电解水的效率很大程度上被析氧反应(OER)的多电子动力学迟缓效应所限制。众所周知,诸如IrOx和RuOx的贵金属材料被认为是一类高活性的OER电催化剂。然而它们的造价昂贵且数量稀少,这很大程度上阻止了它们大规模应用。因此,寻找用来替代贵金属进行OER反应的低成本且持久性强的电催化剂是必要的。本文利用在常温下的共沉淀方法,制备出具有高效电催化性能的氢氧化镍纳米片和铬掺杂镍铁水滑石纳米片电催化剂材料,并分别通过增加缺陷位数和电子离域作用从本质上提升了镍基催化材料的电催化析氧性能。具体研究内容如下:1.电子离域促进层状氢氧化物电催化析氧性能研究对于可持续的能量转换和存储来说发展高性能的析氧反应(OER)电催化剂非常重要。通过掺杂未配对d电子的过渡金属离子,使活性位点附近的电子离域分布,显著地促进镍铁层状双金属氢氧化物(LDH)中活性位点的电子给予并且将电荷转移势垒降低了一个量级以此来获得高性能的OER性能。实验结果表明,铬掺杂的镍铁氢氧化物可以在过电势为235 mV时获得10 mA.cm-2的电流并且获得了约为39mV/dec的低塔菲尔斜率。X射线吸收近边谱(XANES)和理论计算揭示了铬和镍离子间d轨道的重叠可以通过移位镍活性位点的电子结构将约0.3个电子通过π给予从Ni2+转移到邻近的Cr (Fe)离子中,明显降低了水分子的自由吸附能到-1.45 eV,从而获得了高效的OER性能。2.氢氧化镍纳米片电催化析氧性能研究寻求低成本以及高效率的电催化析氧反应(OER)催化剂是我们的目标,因为其在能源储存和清洁能源方面具有应用潜力。通过制备多缺陷的Ni(OH)2纳米片,它较小的特性并具有克服尺度效应的部分能力,且具有更多的表面活性位点并且参与了反应,因此在OER方面表现了好性能。结果显示在1MKOH与0.1M KOH下仅需要285 mV和330 mV的过电势驱动就可以达到10 mA.cm2并且塔菲尔斜率优于IrO2。实验结果表明Ni(OH)2纳米片在不同碱性条件下表现稳定,并且展示了可以在1MKOH条件下连续运行超过15h性能不降的良好稳定性。
[Abstract]:Electrocatalytic hydrolysis is considered to be an important pathway for sustainable and renewable energy transfer and storage. However, the efficiency of electrolytic water is largely limited by the multi-electron kinetic retardation effect of oxygen evolution reaction (OER). It is well known that noble metal materials such as IrOx and RuOx are considered to be a class of highly active OER electrocatalysts. But they are expensive and scarce, which largely prevents them from being used on a large scale. Therefore, it is necessary to find low-cost and durable electrocatalysts to replace precious metals for OER reaction. In this paper, nickel hydroxide nanocrystalline and chromium doped nickel ferronickel hydrotalcite nanocrystalline electrocatalysts were prepared by coprecipitation at room temperature. By increasing the number of defect sites and electron delocalization, the electrocatalytic oxygen evolution properties of nickel based catalysts were improved. The specific contents of the study are as follows: 1. Electron delocalization is very important for the development of high performance oxygen evolution (OER) electrocatalysts for sustainable energy conversion and storage. By doping transition metal ions with unpaired d electrons, the electrons near the active sites are distributed outside the domain. The activity sites in Ni-Fe layered bimetallic hydroxides (LDH) were significantly promoted to give electrons and to reduce the charge transfer barrier by an order of magnitude to obtain high performance OER properties. The experimental results show that, Chromium-doped Ni-Fe hydroxides can obtain a current of 10 mA.cm-2 at an overpotential of 235mV, and a low Taffer slope of about 39mV / dec. X-ray absorption near side spectra (XANES) and theoretical calculations reveal the weight of d orbitals between chromium and nickel ions. About 0.3 electrons can be transferred from Ni _ 2 to the adjacent Cr (Fe) ion by 蟺-giving by translocation of the electronic structure of the active site of nickel. The free adsorption energy of water molecule was reduced to -1.45 EV, and the high performance of OER was obtained. Research on Electrocatalytic oxygen Evolution performance of Nickel hydroxide Nanochip Electrocatalytic Oxygenation (OER) Catalysts with low cost and High efficiency are our goals because of their potential applications in energy storage and clean energy. By preparing Ni (OH) _ 2 nanocrystals with many defects, it has small properties and partial ability to overcome the scale effect, and has more surface active sites and participates in the reaction, so it has good performance in OER. The results show that the overpotential drive of 285mV and 330mV can reach 10 mA.cm2 at 1MKOH and 0.1mKOH, and the Tafer slope is better than that of IrO2. The experimental results show that the Ni (OH) _ 2 nanocrystals are stable under different alkaline conditions, and show good stability that the properties of Ni (OH) _ 2 nanocrystals can run continuously for more than 15 hours under the condition of 1MKOH.
【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】：2017
【分类号】：O643.36

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