过渡金属氧化物三维分级纳米结构的构筑及其电催化性能研究
发布时间：2018-11-15 16:56
【摘要】：能源需求的增加使有限的化石燃料枯竭的负担变得更加沉重,为了寻找环保、可再生的绿色能源,克服未来能源的焦虑,政府鼓励科学家们寻找新的可代替能源。氢作为一种新型绿色资源,具有零碳排放、能量密度高以及高能量转换效率的特点。电解水制氢是零碳排放、大规模产生氢的重要技术之一。但是高纯度、大规模地生产氢具有一定难度,因为电解水反应实际需要一个较高的电位,约为1.8-2 V。这明显大于理论分解电压1.23 V。这个电势电位与催化活性相关,被用来在阳极电极发生析氧反应,在阴极发生析氢反应。因此,活性好、效率高的催化剂必须要在合理的电流密度下,减少电极过电位以确保电解水反应过程变得更节能。到目前为止,对析氢反应来说,铂及类以铂为基础的材料是最好的催化剂。Pt在微不足道的过电位下表现出较高的阴极电流密度。然而,贵金属及其化合物属于稀缺性资源,并且成本较高,这限制了其大规模的应用。大多数的以非贵金属氧化物为基础的电极材料迄今少有作为析氢和析氧的双功能催化,高活性催化剂的报道。这是因为同一电解质环境下,不适当的晶体结构会使电极材料导电性降低,从而阻碍其在全水分解过程中的适用性。因此,设计并构筑具有具有特定形貌结构的高活性、高耐用性、价格低廉的非贵金属催化剂成为当下研究的热点。本文结合当下非贵金属催化剂的研究现状,主要做了以下两方面的进展工作:(1)构筑了 一种新型三维Cu2O @ MnO2核/壳纳米线阵列结构电极。基于三维网状导电基底泡沫铜,在其表面生长Cu2O纳米线阵列作为核芯材料,MnO2纳米片作为包覆层材料。性能优异的的Cu2O @ MnO2 NW/NS阵列具有很高的催化活性和很强的耐久性。在电流密度为10mA/cm2时,过电位为132 mV(相对于标准析氢电位)。这是纯锰氧化物/氢氧化物催化剂活性应用于的析氢反应的第一个示范。此外,仔细分析和表征后,我们发现Cu2O@Mn02NW/NS高活性主要来源于水钠锰矿型MnO2(δ-MnnO2)到Mn(OH)2的演变。在电催化反应中,Mn(OH)2的是高度活跃的析氢催化剂。这些研究结果将为其他锰基催化剂的探索提供了新的试验与理论依据。(2)构筑一种简便的方法在泡沫镍表面原位制备活性高、多层次结构的NiCo2O4纳米线@NiCo02纳米线树枝状结构。基于三维网状导电基底泡沫镍,得到的电极材料表现出分层的树枝状结构,其中NiCo2O4纳米线为骨干,NiCoO2纳米线的分支。所制备的NiCo2O4 @NiCoO2 NW/NW纳米材料具有显著的催化活性和良好的耐久性。在1MKOH电解液中,当电流密度为10mA/cm2时,析氢过电位为165 mV,析氧过电位为291 mV,全水分解电压为1.756 V。这是NiCo2O4@NiCoO2 NW/NW复合树枝状结构的用作双催化功能的电极材料在碱性溶液中的第一次报告。本论文的方法提供了一种简便的方式来探索新的纳米催化剂的应用。
[Abstract]:The growing demand for energy has added to the burden of limited fossil fuel depletion. In an effort to find green, renewable energy and overcome future energy worries, the government has encouraged scientists to look for new alternative sources of energy. As a new green resource, hydrogen has the characteristics of zero carbon emission, high energy density and high energy conversion efficiency. Hydrogen production from electrolytic water is one of the most important technologies to produce hydrogen on a large scale and zero carbon emission. However, it is difficult to produce hydrogen on a large scale with high purity, because the electrolytic water reaction needs a high potential of about 1.8-2 V. This is obviously larger than the theoretical decomposition voltage of 1.23 V. This potential is related to catalytic activity and is used for oxygen evolution at the anode electrode and hydrogen evolution at the cathode. Therefore, the catalyst with good activity and high efficiency must reduce electrode overpotential at reasonable current density to ensure that the process of electrolytic water reaction becomes more energy efficient. So far, platinum and platinum-based materials are the best catalysts for hydrogen evolution. Pt exhibits high cathodic current density at negligible overpotential. However, precious metals and their compounds are rare resources and high cost, which limits their large-scale application. Most electrode materials based on non-noble metal oxides are rarely reported as bifunctional and highly active catalysts for hydrogen evolution and oxygen evolution. This is because under the same electrolyte environment, improper crystal structure will reduce the conductivity of electrode material, thus hindering its applicability in the whole water decomposition process. Therefore, the design and construction of high activity, high durability and low cost non-precious metal catalysts with specific morphology have become a hot topic. According to the current research status of non-noble metal catalysts, the following two advances have been done: (1) A novel three-dimensional Cu2O @ MnO2 nanowire array electrode has been constructed. Cu2O nanowire arrays were grown on the surface of three dimensional netted conductive substrates, and Cu2O nanowires were used as core-core materials and MnO2 nanochips as coating materials. The excellent Cu2O @ MnO2 NW/NS array has high catalytic activity and durability. When the current density is 10mA/cm2, the overpotential is 132 mV (relative to the standard hydrogen evolution potential). This is the first demonstration of the application of pure manganese oxide / hydroxide catalyst activity to hydrogen evolution. In addition, after careful analysis and characterization, we found that the high activity of Cu2O@Mn02NW/NS is mainly due to the evolution from MnO2 (未-MnnO2) to Mn (OH) 2. , Mn (OH) _ 2 is a highly active catalyst for hydrogen evolution in electrocatalytic reactions. These results will provide a new experimental and theoretical basis for the exploration of other manganese based catalysts. (2) A simple method for in-situ preparation of nickel foams has high activity. Multilevel NiCo2O4 nanowires @ NiCo02 nanowire dendrites. Based on the three dimensional netted conductive substrate nickel foam, the electrode material shows a layered dendritic structure, in which NiCo2O4 nanowires are the backbone and NiCoO2 nanowires are branched. The prepared NiCo2O4 @ NiCoO2 NW/NW nanomaterials have remarkable catalytic activity and good durability. In 1MKOH electrolyte, when the current density is 10mA/cm2, the overpotential of hydrogen evolution is 165 mV, oxygen evolution overpotential is 291 mV, the total water decomposition voltage is 1.756 V. This is the first report of the NiCo2O4@NiCoO2 NW/NW composite dendritic structure used as a double catalytic electrode material in alkaline solution. The method in this paper provides a simple way to explore the application of new nano-catalysts.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TQ116.2
本文编号：2333879
[Abstract]:The growing demand for energy has added to the burden of limited fossil fuel depletion. In an effort to find green, renewable energy and overcome future energy worries, the government has encouraged scientists to look for new alternative sources of energy. As a new green resource, hydrogen has the characteristics of zero carbon emission, high energy density and high energy conversion efficiency. Hydrogen production from electrolytic water is one of the most important technologies to produce hydrogen on a large scale and zero carbon emission. However, it is difficult to produce hydrogen on a large scale with high purity, because the electrolytic water reaction needs a high potential of about 1.8-2 V. This is obviously larger than the theoretical decomposition voltage of 1.23 V. This potential is related to catalytic activity and is used for oxygen evolution at the anode electrode and hydrogen evolution at the cathode. Therefore, the catalyst with good activity and high efficiency must reduce electrode overpotential at reasonable current density to ensure that the process of electrolytic water reaction becomes more energy efficient. So far, platinum and platinum-based materials are the best catalysts for hydrogen evolution. Pt exhibits high cathodic current density at negligible overpotential. However, precious metals and their compounds are rare resources and high cost, which limits their large-scale application. Most electrode materials based on non-noble metal oxides are rarely reported as bifunctional and highly active catalysts for hydrogen evolution and oxygen evolution. This is because under the same electrolyte environment, improper crystal structure will reduce the conductivity of electrode material, thus hindering its applicability in the whole water decomposition process. Therefore, the design and construction of high activity, high durability and low cost non-precious metal catalysts with specific morphology have become a hot topic. According to the current research status of non-noble metal catalysts, the following two advances have been done: (1) A novel three-dimensional Cu2O @ MnO2 nanowire array electrode has been constructed. Cu2O nanowire arrays were grown on the surface of three dimensional netted conductive substrates, and Cu2O nanowires were used as core-core materials and MnO2 nanochips as coating materials. The excellent Cu2O @ MnO2 NW/NS array has high catalytic activity and durability. When the current density is 10mA/cm2, the overpotential is 132 mV (relative to the standard hydrogen evolution potential). This is the first demonstration of the application of pure manganese oxide / hydroxide catalyst activity to hydrogen evolution. In addition, after careful analysis and characterization, we found that the high activity of Cu2O@Mn02NW/NS is mainly due to the evolution from MnO2 (未-MnnO2) to Mn (OH) 2. , Mn (OH) _ 2 is a highly active catalyst for hydrogen evolution in electrocatalytic reactions. These results will provide a new experimental and theoretical basis for the exploration of other manganese based catalysts. (2) A simple method for in-situ preparation of nickel foams has high activity. Multilevel NiCo2O4 nanowires @ NiCo02 nanowire dendrites. Based on the three dimensional netted conductive substrate nickel foam, the electrode material shows a layered dendritic structure, in which NiCo2O4 nanowires are the backbone and NiCoO2 nanowires are branched. The prepared NiCo2O4 @ NiCoO2 NW/NW nanomaterials have remarkable catalytic activity and good durability. In 1MKOH electrolyte, when the current density is 10mA/cm2, the overpotential of hydrogen evolution is 165 mV, oxygen evolution overpotential is 291 mV, the total water decomposition voltage is 1.756 V. This is the first report of the NiCo2O4@NiCoO2 NW/NW composite dendritic structure used as a double catalytic electrode material in alkaline solution. The method in this paper provides a simple way to explore the application of new nano-catalysts.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TQ116.2
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