【作者】 罗琼；

【导师】 彭明营；

【作者基本信息】 华南理工大学 ， 材料学， 2016， 硕士

【摘要】 纳米材料具有较大的比表面积,能显著提高电催化效率,因而在电催化研究中受到了广泛关注。随着能源需求的持续增加,化石燃料的不断消耗以及环境问题的日益严重,亟需发展可再生的清洁能源。燃料电池和氢气是高效、环保的二次能源,是能源研究领域的热点。因此发展可用于甲醇氧化、电解水制氢等电化学系统的新型纳米电催化剂,是推动这些清洁能源迈向商业化应用的关键一步。过渡金属镍在地壳的储量丰富（其含量仅次于硅、氧、铁、镁,居第5位）,价格低廉,且镍及其化合物具有优越的电化学性质,能有效降低电催化反应的过电势,有望替代传统的贵金属用于电催化系统的电极材料。本文主要围绕镍基纳米自支撑电极的制备,并系研究了其甲醇氧化和水分解等电催化性能。主要研究结果如下:1、通过水热和煅烧等技术,首次在泡沫镍上原位生长出氧化镍纳米片@纳米线核壳结构（NiO nanosheet@nanowire arrays on Ni foam,NiO NS@NW/NF）,成功构建了三维自支撑电极。当该三维电极直接用于碱性甲醇氧化时,NiO NS@NW/NF电极在电势为1.62 V（相对于标准氢电极RHE）时电流密度达到89 mA cm^-2,是泡沫镍(30 mA cm^-2)的3倍。NiO NS@NW/NF电极优秀的电催化性能是由于NiO纳米阵列的核壳分层结构,加上在泡沫镍上原位生长构建出自支撑电极,使得该电极具有更多的活性位点,同时能够促进反应中的传质过程。2、采用水热法成功构建了NiO/Ni,Ni3S2/Ni,NiSe/Ni自支撑电极,系统研究了NiO、Ni3S2、NiSe纳米线对甲醇氧化反应的电催化性能,发现其性能关系为NiSe>Ni3S2>NiO。把NiSe/Ni自支撑电极用于甲醇氧化时,它显示出优秀的电催化性能,在1 M KOH+0.5 M CH₃OH的电解液中,当电势为0.5 V（相对于饱和甘汞电极SCE）时电流密度能达到132 mA cm^-2,是Ni箔(32 mA cm^-2)的4倍。3、在同种电解液中同时实现对析氧反应（OER）和析氢反应（HER）的有效电催化,是非常具有挑战性的工作,目前报道很少。我们采用电沉积法在泡沫镍上合成出NiFe纳米片,成功构建了NiFe/NF自支撑电极（NiFe nanosheets film on Ni foam,NiFe/NF）。Ni Fe/NF三维电极在碱性溶液中同时表现出高效的OER和HER催化活性,在1 M KOH溶液中,OER过程中达到电流密度20 mA cm^-2时仅需过电势264 mV;同时HER过程中达到电流密度10 mA cm^-2时仅需过电势139 mV。NiFe/NF电极的双功能性启发我们将其同时用作阳极和阴极构建碱性电解水槽。该电解槽电分解水时电流密度达到10 mA cm^-2仅需电势1.64 V,性能优于之前报道的NiFe LDH组装的电解槽（1.7 V）。更多还原

【Abstract】 With high surface areas, nanostructured materials can effectively improve the catalytic activity, thus have received widespread interest in electrocatalysis. Nowdays, with the tremendous growth of demand for energy, depletion of fossil fuels and worsened environmental pollution, it is urgent to develop renewable clean energy sources. Fuel cell and hydrogen, as high energy efficiency and environmentally friendly secondary energy, have been a hot topic in the field of energy research. Thus it is important to develop new type of nano electrocatalyst for electrochemical systems, such as direct methanol fuel cell and water splitting devices, which is a key step to promote commercial use of these clean energy. Earth-abundant transition metal nickel（Ni） and its compounds are an interesting non-noble-metal alternative, because of its cost effectiveness（global Ni reserves are just less than silicon, oxygen, iron and magnesium, ranking fifth） and high electrocatalytic activity. In this thesis, we describe the fabrication of Ni based nano self-supporting electrode and their application in electro-oxidation of methanol and electro-catalytic water splitting.The main research results are as following:1. We describe the first fabrication of nickel oxide nanosheet@nanowire arrays on Ni foam（Ni O NS@NW/NF） through a hydrothermal process followed by annealing treatment, thus obtain 3D self-supporting electrode. When directly used it as anode for electro-oxidation of methanol, the Ni O NS@NW/NF electrode exhibits high catalytic activity and stability, affording a current density of 89 m A cm^-2 at 1.62 V（vs. RHE） in 1 M KOH with 0.5 M methanol, which is 3 times higher than that of NF(30 m A cm^-2). In addition, the hierarchical architecture of Ni O and 3D self-supporting configuration of this electrode favors the exposure of more active sites and facilitates sufficient transport of reactants and products, resulting in high electrocatalytic activity.2. We develop a simple solvothermal method for configuration of Ni O/Ni, Ni3S2/Ni, Ni Se/Ni self-supporting electrodes. The electro-catalytic performance of nickel chalcogenides（Ni O, Ni3S2, Ni Se） nanowires is also systematic studied and the electro-catalytic activity is in the order of Ni Se > Ni3S2 > Ni O. When used as a 3D self-supporting anode for electro-catalytic oxidation of methanol, the Ni Se/Ni achieves a current density of 132 m A cm^-2 at 0.5 V（vs. SCE） in 1 M KOH with 0.5 M methanol, which is 4 times higher than that of NF(32 m A cm^-2).3. It is still a challenge to realize efficient electro-catalyic water splitting in the same electrolyte, including oxygen evolution reaction（OER） and hydrogen evolution reaction（HER）, which has been rarely reported so far. In this chapter, we report a 3D self-supporting electrode prepared by a versatile and one-step electrodeposition of Ni Fe nanosheets film on NF substrate（Ni Fe/NF）. The Ni Fe/NF shows high catalytic activity for both OER and HER in basic media, and it only needs overpotentials of 264 m V to afford 20 m A cm^-2 for OER and 139 m V to deliver 10 m A cm^-2 for HER in 1 M KOH. Inspired by the bifunctional activity of Ni Fe/NF, we constructed an alkaline water electrolyzer using Ni Fe/NF as catalyst for both anode and cathode. This electrolyzer splits water with a current density of 10 m A cm^-2 at 1.64 V, which is superior to that of Ni Fe LDH/NF（1.7 V）.更多还原