NiFe基微球形层状复合氢氧化物—氧化物的制备及析氧性能研究
发布时间：2019-02-26 14:54
【摘要】：氢能是一种清洁的无碳能源,具有储量广、热值高和绿色环保等优点,是一种理想的可再生非化石能源,然而目前氢能大规模应用面临廉价制氢、安全储氢和高效用氢三个问题。在制氢方面,电解水制氢因氢气纯度高、绿色环保和工艺简单等优点而倍受关注,但是其能耗过大严重制约着其规模化应用。能耗高的主要原因是电解池阳极催化剂的析氧超电势过高。虽然Ru和Ir基贵金属催化剂能有效降低超电势,但其探明储量少且价格高昂,难以实现大规模应用,因此,开发一类活性高且稳定性好的廉价非贵金属析氧电催化剂具有重要的科学意义和实际应用价值。层状复合金属氢氧化物(LDHs)是一种层板组成可调变、层间客体可交换的二维层状结构材料,而且已有文献报道含Co、Ni、Fe或Mn等过渡金属元素的LDHs材料或其焙烧产物MMO具有突出的析氧电催化性能(活性和稳定性)。但是,LDHs类材料容易发生团聚,导致有效比表面减小和稳定性下降,不利于其活性组分析氧性能的充分发挥,因此,如何可控制备不易团聚的中空微球多级结构的高析氧性能的LDHs材料或其焙烧产物是件亟待解决的关键问题。本文基于无模板法一步水热合成了Ni2Fe-LDH与CoxNi2-xFe-LDH中空微球材料,并对LDHs前驱体进行热处理得到混合金属氧化物中空微球,通过ICP-AES、XRD、SEM以及TEM等手段对样品组成、结构、形貌等进行详细表征与分析,采用旋转盘电极、循环伏安和线性扫描等电化学技术对样品在碱性电解质电催化性能进行表征与分析。本文的主要研究结果如下:(1)以 Ni(N03)2·6H20、Fe(N03)3·9H20 为原料,NH4F 为形貌调控剂,CO(NH2)2为沉淀剂,通过一步水热合成法可控制得了 Ni2Fe-LDH中空微球。所制得的微球直径尺寸在7～9 μm范围内,组成微球的LDH片的大小约为1 μm。研究结果表明,NH4F在微球形成的过程中同时起到形貌调控与化学诱导自转变作用,基于反应时间的实验证实微球的形成原理是Ostwald熟化。尽管在形成中空微球的过程中比表面是减少的,但是独特的多级结构导致电化学活性面积增大,当NH4F浓度为0.4 M时,Ni2Fe-LDH中空微球的OER活性最佳,其在1 mol.L-1的KOH溶液中的η10超电势仅为290 mV, Tafel斜率为51 mV·dec-1,优于贵金属Ru02的性能。此外,经过2000次CV循环后其η10超电势仅增加12.9%,表现出了优异的电催化稳定性。(2)以 Co(N03)2·6H2O、Ni(N03)2.6H2O、Fe(N03)3·9H20 为原料,NH4F为形貌调控剂,CO(NH2)2为沉淀剂,通过一步水热合成法制得不同Co、Ni比例的CoxNi2-xFe-LDH中空微球材料。研究结果表明,引入的Co2+导致高导电性的NiⅢOOH在低电位更容易生成,其中Co1Ni1Fe-LDH中空微球样品的OER活性达到最高,η10超电势为290 mV。以CoxNi2-xFe-LDH为前驱体,通过不同温度焙烧得到系列不同组成的ComNi2-mFeOx-MMO中空微球材料,前驱体的形貌得到完全保留。当焙烧温度的升高至700℃时开始逐渐出现烧结现象,在一定程度上降低样品的电化学活性面积从而使OER与ORR活性下降。经600℃焙烧得到的Co0.75Ni1.25FeOx-MMO材料具备最低的ΔE(EOER-EoRR)为0.95 V,优于贵金属氧化物IrO2材料(1.32 V),非常接近商业Pt/C (0.94V)的ΔE值。
[Abstract]:Hydrogen energy is a kind of clean carbon-free energy, has the advantages of wide storage, high heat value and green and environmental protection, is an ideal renewable non-fossil energy source, but at present, the hydrogen energy large-scale application is faced with the three problems of cheap hydrogen production, safe hydrogen storage and high-efficiency hydrogen production. In the aspect of hydrogen production, the hydrogen production of the electrolyzed water is of great concern due to the high purity of the hydrogen, the green environment protection and the simple process, but the energy consumption of the water is too large to restrict the large-scale application. The main reason for high energy consumption is that the oxygen evolution of the anode catalyst of the electrolytic cell is too high. Although the Ru and Ir-based noble metal catalysts can effectively reduce the overpotential, it is difficult to realize large-scale application, and therefore, it is of great scientific significance and practical application value to develop a kind of cheap non-noble metal oxygen-removing electrocatalyst with high activity and good stability. the layered composite metal hydroxide (LDHs) is a two-dimensional layered structure material which is composed of a laminate, an adjustable variable layer and a layer-to-layer object, and has been reported to contain Co, Ni, The LDHs material of a transition metal element such as Fe or Mn or the roasting product MMO thereof has a prominent oxygen evolution electrocatalytic performance (activity and stability). however, that LDHs material is easily agglomerated, resulting in a decrease in the effective specific surface and a decrease in stability, which is not conducive to the full play of the activity group in the analysis of the oxygen performance, and therefore, How to control the high-oxygen-performance LDHs material of a hollow micro-sphere multi-stage structure which is not easy to be agglomerated or the roasting product of the LDHs material is a key problem to be solved urgently. The hollow micro-spheres of Ni2Fe-LDH and CoxNi2-xFe-LDH were synthesized by heat treatment of LDHs precursor, and the composition, structure and morphology of the samples were characterized and analyzed by ICP-AES, XRD, SEM and TEM. The electrocatalytic properties of the samples were characterized and analyzed by electrochemical techniques such as rotating disk electrode, cyclic voltammetry and linear scanning. The main results of this paper are as follows: (1) Ni (N03) 2 路 6H20, Fe (N03) 3 路 9H20 as raw material, NH4F as the profile control agent and CO (NH2) 2 as precipitant, Ni2Fe-LDH hollow microspheres can be controlled by one-step hydrothermal synthesis. The size of the prepared micro-ball is in the range of 7-9. m u.m, and the size of the LDH sheet making up the micro-ball is about 1. m Based on the reaction time, the formation principle of microball is confirmed by Ostwald ripening. Although the specific surface is reduced during the formation of the hollow microspheres, the unique multi-stage structure results in an increase in the area of the electrochemically active area, and when the concentration of the NH4F is 0.4 M, the OER activity of the Ni2Fe-LDH hollow microspheres is best, and the OER potential in the KOH solution of 1 mol. L-1 is only 290 mV, The Tafel slope is 51 mV. dec-1, which is superior to the properties of the noble metal Ru02. In addition, after the 2000 CV cycle, the over-potential of the capacitor 10 increased by only 12. 9%, showing excellent electrocatalytic stability. (2) Co (N03) 2.6H2O, Ni (N03) 2.6H2O, Fe (N03) 3.9H20 as the raw material, the NH4F as the profile control agent, CO (NH2) 2 as a precipitating agent, and the CoxNi2-xFe-LDH hollow microsphere material with different Co and Ni ratio is prepared by one-step hydrothermal synthesis method. The results show that the introduced Co2 + results in the high conductivity of Ni-鈪，
本文编号：2430884
[Abstract]:Hydrogen energy is a kind of clean carbon-free energy, has the advantages of wide storage, high heat value and green and environmental protection, is an ideal renewable non-fossil energy source, but at present, the hydrogen energy large-scale application is faced with the three problems of cheap hydrogen production, safe hydrogen storage and high-efficiency hydrogen production. In the aspect of hydrogen production, the hydrogen production of the electrolyzed water is of great concern due to the high purity of the hydrogen, the green environment protection and the simple process, but the energy consumption of the water is too large to restrict the large-scale application. The main reason for high energy consumption is that the oxygen evolution of the anode catalyst of the electrolytic cell is too high. Although the Ru and Ir-based noble metal catalysts can effectively reduce the overpotential, it is difficult to realize large-scale application, and therefore, it is of great scientific significance and practical application value to develop a kind of cheap non-noble metal oxygen-removing electrocatalyst with high activity and good stability. the layered composite metal hydroxide (LDHs) is a two-dimensional layered structure material which is composed of a laminate, an adjustable variable layer and a layer-to-layer object, and has been reported to contain Co, Ni, The LDHs material of a transition metal element such as Fe or Mn or the roasting product MMO thereof has a prominent oxygen evolution electrocatalytic performance (activity and stability). however, that LDHs material is easily agglomerated, resulting in a decrease in the effective specific surface and a decrease in stability, which is not conducive to the full play of the activity group in the analysis of the oxygen performance, and therefore, How to control the high-oxygen-performance LDHs material of a hollow micro-sphere multi-stage structure which is not easy to be agglomerated or the roasting product of the LDHs material is a key problem to be solved urgently. The hollow micro-spheres of Ni2Fe-LDH and CoxNi2-xFe-LDH were synthesized by heat treatment of LDHs precursor, and the composition, structure and morphology of the samples were characterized and analyzed by ICP-AES, XRD, SEM and TEM. The electrocatalytic properties of the samples were characterized and analyzed by electrochemical techniques such as rotating disk electrode, cyclic voltammetry and linear scanning. The main results of this paper are as follows: (1) Ni (N03) 2 路 6H20, Fe (N03) 3 路 9H20 as raw material, NH4F as the profile control agent and CO (NH2) 2 as precipitant, Ni2Fe-LDH hollow microspheres can be controlled by one-step hydrothermal synthesis. The size of the prepared micro-ball is in the range of 7-9. m u.m, and the size of the LDH sheet making up the micro-ball is about 1. m Based on the reaction time, the formation principle of microball is confirmed by Ostwald ripening. Although the specific surface is reduced during the formation of the hollow microspheres, the unique multi-stage structure results in an increase in the area of the electrochemically active area, and when the concentration of the NH4F is 0.4 M, the OER activity of the Ni2Fe-LDH hollow microspheres is best, and the OER potential in the KOH solution of 1 mol. L-1 is only 290 mV, The Tafel slope is 51 mV. dec-1, which is superior to the properties of the noble metal Ru02. In addition, after the 2000 CV cycle, the over-potential of the capacitor 10 increased by only 12. 9%, showing excellent electrocatalytic stability. (2) Co (N03) 2.6H2O, Ni (N03) 2.6H2O, Fe (N03) 3.9H20 as the raw material, the NH4F as the profile control agent, CO (NH2) 2 as a precipitating agent, and the CoxNi2-xFe-LDH hollow microsphere material with different Co and Ni ratio is prepared by one-step hydrothermal synthesis method. The results show that the introduced Co2 + results in the high conductivity of Ni-鈪，
本文编号：2430884
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