【作者】 何斌；

【导师】 郝青丽； 苏志；

【作者基本信息】 南京理工大学 ， 化学工程与技术， 2022， 博士

【摘要】 开发新型绿色能源和降低对化石燃料依赖是实现可持续发展的必由之路。现如今,人们对制备成本低廉且高效的电化学催化剂展现出越来越浓厚的兴趣,这些催化剂可以应用在一些可持续能源装置与技术中,比如:电催化水分解,金属空气燃料电池,锂电池等。过渡金属钴基催化剂与贵金属催化剂相比,其储量丰富,成本低廉且高活性等特性被认为是一种具有广阔应用前景的电化学催化剂。钴基金属有机骨架（MOFs）是一种由金属离子和有机配体通过配位键连接而形成的三维（3D）网络框架材料。MOFs材料因具有多孔、孔隙结构有序、孔径均匀和比表面积大等特点,有利于促进反应底物快速运输和扩散从而被应用于多个研究领域。本论文采用模板法制备了一系列不同形貌和组分的钴基催化剂,并研究其电催化水分解析氢反应（HER）以及析氧反应（OER）性能。具体研究内容如下:1.合理构建异质界面Ni₂P-Co₂P-Fe₂P（NiCoFeP-HN）中空纳米棱柱,并应用为OER电催化剂。室温下,镍钴前驱体与[Fe（CN）₆]^3-发生原位离子交换反应,然后在N₂氛围中300℃下进行磷化处理生成NiCoFeP-HN。通过实验表征证明离子交换过程是保持纳米形貌和提高OER性能的重要过程。与商业化的Ru O₂+Pt/C锌-空气电池相比,NiCoFeP-HN+Pt/C构建的锌-空气电池具有更高的能量密度和更好的循环稳定性。本研究为构造空心纳米结构和异质结复合物提供了一种简便、高效的方法。2.以ZIF-67-Co为模板,通过磷化[Fe（CN）₆]^3-与NiCo-LDH（层状双氢氧化物）交换产物合成了Fe掺杂的NiCo P杂化中空纳米笼（简称Fe-NiCo P）。Fe-NiCo P催化剂在1.0 M KOH溶液中表现出良好的HER和OER活性,在10 m A·cm^-2下所需过电位分别为147 m V和235 m V。此外,Fe-NiCo P催化剂在电流密度为10 m A·cm^-2下的电压仅为1.60 V。Fe-NiCo P+Pt/C催化剂构建的锌-空气电池在电流密度为5 m A·cm^-2下表现出良好的循环稳定性,其性能明显优于Ru O₂+Pt/C催化剂。3.在H₂/Ar混合气氛下,通过对Fe蚀刻后的ZIF-67进行碲化,得到Fe掺杂碲化钴纳米颗粒镶嵌的氮掺杂碳纳米管框架(Fe-Co_1.11Te₂@NCNTF)。Fe掺杂能够有效调节Co_1.11Te₂的电子结构,提高反应活性,进一步提高电化学性能。Fe-Co_1.11Te₂@NCNTF样品在电流密度为10 m A·cm^-2条件下的HER和OER过电势分别为107和297 m V,性能优于未掺杂的Co_1.11Te₂@NCNTF（分别为165和360 m V）。Fe-Co_1.11Te₂@NCNTF-2样品在电流密度为10 m A·cm^-2条件下的全解水电压仅为1.61V。密度函数理论（DFT）计算表明,Fe掺杂不仅提供了丰富的活性位点,而且降低了氢结合自由能。这项工作为研究用于高效整体水分解的非贵金属催化剂提供了一种可行的方法。4.先将NiCo-BTC MOF煅烧成多层空心NiCo₂O₄微球,然后在NH₄HCO₃存在下直接硫化得到氮掺杂的氧化/硫化物异质结材料（命名为N-NiCo₂S₄/Co O微球）。由于氮的掺杂、多层中空异质结构以及多组分之间的界面协同作用,在10 m A·cm^-2时其表现出良好的OER活性,过电位仅为238 m V。N-NiCo₂S₄/Co O+Pt/C催化剂组装成的锌-空气电池在5 m A·cm^-2的电流密度下循环900次后依然保持良好性能,稳定性优于Ru O₂+Pt/C催化剂,这表明其作为能源器件具有很大的应用潜力。5.以CoFe-PBA为前驱体,通过离子交换反应和随后的磷化过程成功合成了Ru掺杂CoFeP纳米立方体（Ru-CoFeP）。在Ru掺杂、多孔结构和高密度活性位点的协同作用下,制备的Ru-CoFeP纳米立方体具有良好的OER活性,在10 m A·cm^-2下过电位为185 m V,具有良好的稳定性。DFT计算表明,Ru的引入使得CoFeP活性位点周围的电子云密度增加,使其对H₂O分子的吸附能力增强,更容易实现O-H键的拉长以及断裂,从而提高OER的性能。此外,在电流密度为5 m A·cm^-2时,Ru-CoFeP+Pt/C基电池的表现出较好的循环稳定性,优于Ru O₂+Pt/C基电池。更多还原

【Abstract】 Developing new green energy and reducing dependence on fossil fuels is the only way to achieve sustainable development.Nowadays,there is an interest in the preparation of cost-effective and efficient electrochemical catalysts for sustainable energy devices and technologies such as electrocatalytic water decomposition,metal-air batteries,and Li-batteries.Compared with noble metal catalysts,transition metal cobalt-based catalysts are considered to be promising electrochemical catalysts because of their abundant reserves,low cost and high activity.Cobalt-based Metal organic frameworks（MOFs）are three-dimensional（3D）network framework materials formed by metal ions and organic ligands through coordination bonds.MOFs materials have the characteristics of porosity,orderly pore structure,uniform pore size and large specific surface area,which is conducive to promoting the rapid transport and diffusion of reactants and has been applied in many research fields,especially in the field of electrochemistry.In this dissertation,cobalt-based catalysts with different morphologies and components were prepared by template method,and their performance for electrocatalytic water separation hydrogen reaction（HER）and oxygen evolution reaction（OER）were studied.The main results are summarized as follows:1.Rational construction of hierarchical Ni₂P-Co₂P-Fe₂P hybrid hollow nanoprism（abbreviated as NiCoFeP-HN）,which could efficiently work as the OER electrocatalysts.NiCoFeP-HN was synthesized via in situ ion exchange reaction of nickel-cobalt precursors with[Fe（CN）₆]^3-at room temperature and followed the subsequent phosphorization treatment at 300°C under N₂.The ion exchange procedure was found to be crucial to preserve the nanoprism morphology and enhance OER performance.Comparing to the conventional Ru O2+Pt/C Zn-air battery,NiCoFeP-HN+Pt/C based Zn-air battery has exhibited superior energy density and much better cycling stability.This work provided a facile and efficient avenue for the construction of hollow nanostructure and hybrid composition.2.Fe-doped NiCo P hybrid hollow nanocage（denoted as Fe-NiCo P）was synthesized through the phosphorization of the product from[Fe（CN）₆]^3-intercalated NiCo-LDH（layered double hydroxide）,where original ZIF-67-Co was used as the template.Owing to the hollow nanostructure and the synergistic effect between multiple components,the Fe-NiCo P catalyst exhibited promising HER and OER activities in 1.0 M KOH with the low overpotentials of 147 and 235 m V at 10 m A·cm^-2,respectively.Furthermore,Fe-NiCo P catalyst only achieve the current density of 10 m A·cm^-2 at the voltage of 1.60 V.The Zn-air battery constructed by Fe-NiCo P+Pt/C catalyst showed good cycling stability at the current density of 5 m A·cm^-2,and its performance was significantly better than that of Ru O₂+Pt/C catalyst.3.Fe-doped cobalt telluride nanoparticles encapsulated in nitrogen-doped carbon nanotube frameworks(Fe-Co_1.11Te₂@NCNTF)by tellurized of Fe-etched ZIF-67 under a mixed H₂/Ar atmosphere.Fe-doping was able to effectively modulate the electronic structure of Co_1.11Te₂,increase the reaction activity,and further improve the electrochemical performance.The optimized electrocatalyst exhibited superior HER and OER performances in an alkaline electrolyte with low overpotentials of 107 and 297 m V with a current density of 10 m A·cm^-2,in contrast to the undoped Co_1.11Te₂@NCNTF of 165 and 360 m V,respectively.The overall water splitting performance only required a voltage of 1.61 V to drive a current density of 10 m A·cm^-2.Density function theory（DFT）calculations indicated that the Fe-doping not only afforded rich exposed active sites but also decreased the hydrogen binding free energy.This work provided a feasible way to study non-precious-metal catalysts for an efficient overall water splitting.4.The nitrogen doped oxide/sulfide heterostructures（named N-NiCo₂S₄/Co O microsphere）microsphere was synthesized from annealing the NiCo-BTC MOF to multi-layered hollow structure of NiCo₂O₄microsphere,following the directly vulcanizing in the presence of NH₄HCO₃ to the resulted oxide/sulfide heterojunction.Benefiting from the nitrogen doping,the abundant multi-layered hollow heterostructure and the interfaces between multiple components,the N-NiCo₂S₄/Co O microsphere exhibited excellent OER activity with a low overpotential of 238 m V at 10 m A·cm^-2.The Zn-air battery based on the N-NiCo₂S₄/Co O+Pt/C catalyst displayed excellent cycling stability at the large current density of 5 m A·cm^-2,and its stability was superior to that of Ru O₂+Pt/C catalyst,suggesting the great potential application as the power source devices.5.Ru doped CoFeP nanocubes（Ru-CoFeP）were successfully synthesized by ion exchange reaction and phosphating process using CoFe-PBA as precursor.Benefitting from the synergistic effects of the Ru doping,porous structure and high density of active sites,the Ru-CoFeP nanocube exhibited excellent OER activity with a small overpotential of 185 m V at 10 m A·cm^-2 and superior long-term durability.Density functional theory（DFT）calculations revealed that the electrons would move toward to Ru after the Ru doping on the active Ru-CoFeP surface and the adsorption capacity to H₂O molecules was also strengthened to elongate and break O-H bond to enhance the OER performance.Furthermore,the cycle stability of Ru-CoFeP+Pt/C-based battery at the current density of 5 m A·cm^-2exhibited much durability,which was superior to that of the Ru O₂+Pt/C-based battery.更多还原