论文总字数：35290字

摘 要

钙钛矿型催化剂具有较高的氧还原活性、良好的热稳定性、储氧性能和低廉的成本等优点，已成为目前锌-空气电池催化剂研究的一大热点。选择和制备高效的空气电极催化剂，改善空气电极的极化特性，提高电池的工作电压及开路电压，是实现锌空气电池推广应用的关键。本文从镧系钙钛矿型催化剂的制备工艺和A位掺杂改性两个方面进行研究。以钙钛矿型催化剂LaMnO₃为研究对象，采用表面活性剂PEG-2000辅助溶胶-凝胶法，从煅烧时间、煅烧温度、初始溶液pH值和表面活性剂含量四个因素出发，探究了钙钛矿型催化剂的制备工艺，并对钙钛矿的A位掺杂Sr进行了研究，利用热分析、XRD和TEM对制备过程影响因素和催化剂的物相组成、晶体结构及一次颗粒粒径状况进行了分析，并借助氧还原极化曲线，探讨了其作为空气电极催化剂的电化学性能。

LaMnO₃催化剂的制备工艺研究表明：煅烧温度、煅烧时间、初始溶液的pH值和表面活性剂的加入均对材料电催化性能有一定影响。该材料钙钛矿晶体在650℃已成型，无杂相；表面活性剂聚乙二醇-2000对电催化性能有很大改观，终止极化电流密度从未添加分散剂时的85mA/cm^-2（850℃下煅烧）增至212mA/cm^-2（700℃下煅烧），增幅可达152%。本文确定使用表面活性剂辅助溶胶-凝胶法制备LaMnO₃钙钛矿型催化剂的最佳工艺参数为：煅烧温度700℃、煅烧时间3小时、初始溶液pH值为6.5和表面活性剂添加量相对金属离子的摩尔比为0.018。

La_0.8Sr_0.2MnO₃粉体在无水乙醇介质中的分散性能研究表明：在外加分散剂（十六烷基三甲基溴化铵、三乙醇胺、十二烷基苯磺酸钠、聚乙二醇-2000、硬脂酸和聚乙烯吡咯烷酮）的作用下，随超声时间增加，粉末的吸光度呈波动式增大后缓慢下降。232 nm 是La_0.8Sr_0.2MnO₃催化剂粉末的最佳测量波长。当分散剂的添加量为5wt%时，5wt% La_0.8Sr_0.2MnO₃粉末乙醇溶液最佳分散剂为硬脂酸，最佳超声时间为90min。

在LaMnO₃的A位进行Sr掺杂研究表明：所得到的仍为钙钛矿型晶体，其晶体成型温度在450℃左右，700℃下煅烧的晶粒尺寸处于纳米级别（10~20nm）。研究发现：随着Sr掺杂量的增加，催化剂的电化学性能先变好后变差，而晶粒尺寸、晶格畸变程度也呈现类似倒U型的趋势，其峰值位置在20%的A位Sr掺杂处。

以700℃ 为煅烧温度、以3小时为煅烧时间、初始溶液pH值为8和表面活性剂添加量相对金属离子的摩尔比为0.018，采用Pechini法制备的La_xSr_1-xMnO₃系列催化剂中，以La_0.8Sr_0.2MnO₃的电催化性能最好，用线性扫描伏安法测试极化曲线时，当极化电压为-0.6V，氧还原反应极化电流密度可达了207mA/cm^-2，与最佳工艺制备的LaMnO₃电催化性能相当。

关键词：锌-空气电池 空气扩散电极 溶胶-凝胶法 镧系钙钛矿型催化剂 性能

ABSTRACT

Perovskite-type catalysts have the advantages of high oxygen reduction reaction activity, good thermal stability, large oxygen storage capacity and low cost, which thus has become a hot spot in the research field of zinc-air battery catalysts. To select and prepare high-performance air electrode catalyst, to improve polarization characteristics of air electrode and to rise the working voltage and open circuit voltage of the battery are the key technology to realize the extensive application of zinc-air battery. In this paper, two aspects which include the preparation technology of the perovskite-type catalyst and the modification of A-site doping had been studied. Perovskite-type catalysts LaMnO₃ is taken as the object of study with surfactant (PEG-2000) assisted sol-gel method and the preparation of perovskite- type catalysts in view of calcination time, calcination temperature, the initial pH value and surface active agent was probed into. And the A-site Sr-doped perovskites were measured by thermal analysis, XRD and TEM to figure out the influence factors of preparation process, phase composition, crystal structure and particle size of the catalysts. With the help of oxygen reduction reaction polarization curve, electrochemical performance of air electrode catalysts was discussed.

The study on preparation technology of LaMnO₃ catalyst shows that calcination time, calcination temperature, the initial pH value and surface active agent all have some effects on the electrocatalysis of the materials. When calcination temperature is 650℃, perovskite crystal has been formed with no impurity phases. The addition of surfactant PEG-2000 can greatly improve electricity catalytic performance, the terminal polarization current density changing from 85mA/cm^-2 (corresponding to 850℃ without dispersant) to 212mA/cm^-2 (corresponding to 700℃), with an increase of about 152%。Thus, this paper determines best techniques of the perovskite-type catalysts LaMnO₃ preparation with surfactant (PEG-2000) assisted sol-gel method: calcining temperature is 700℃, calcining time is 3 hours, the initial pH value is 6.5 and the molar ratio of the surface active agent in proportion to the metal ions is 0.018.

The study on the dispersion properties of La_0.8Sr_0.2MnO₃ catalyst in ethanol solution shows that when dispersing agent (cetyltrimethylammonium bromide, triethanolamine, sodium dodecyl benzene sulfonate, PEG-2000, stearic acid and polyvinylpyrrolidone) is added respectively, the absorbance of the superfine powder of catalyst experiences a wave-type rise, and then slowly drops with the increase of ultrasonic time. The best measuring wavelength of La_0.8Sr_0.2MnO₃ catalyst powder is 232 nm. When the adding amount of dispersant is 5wt%, the best dispersing agent of 5wt% La_0.8Sr_0.2MnO₃ ethanol solution is stearic acid, and the optimum ultrasonic time is 90 minutes.

The study on A-site Sr-doped LaMnO₃ shows that displacement type solid solution that we obtained is still perovskite-type crystal, whose crystal forming temperature is about 450℃ and grain size is nano-scale (10 ~ 20nm) when calcined at 700℃. With the doping amount of Sr increasing, electrochemical performance of catalysts become better and then worse later on. Grain size and lattice distortion degree also appears similarly as an inverted U-shape, with its peak position in 20 per cent of Sr-doping.

When calcination temperature is 700 ℃, calcination time is 3 hours, initial solution pH value is 8 and the molar ratio of surface active agent in proportion to the metal ions is 0.018, the electrocatalytic properties of La_0.8Sr_0.2MnO₃ is best among the La_xSr_1-xMnO₃ prepared by pechini method. When measured by linear sweep voltammetry, when the polarization voltage reaches to -0.6V on the polarization curve, oxygen reduction polarization current density arrives at 207mA/cm^-2, which is close to the electrocatalytic properties of LaMnO₃ prepared by the optimal process.

Key Words: Zinc-Air Cell; Air Diffusion Electrode; Sol-Gel; Lanthanide Series Perovskite-type Catalyst; Performance

目 录

摘 要 I

ABSTRACT III

目 录 V

第一章 绪论 1

1.1 引言 1

1.2 氧电极过程 2

1.2.1 氧还原反应 2

1.2.2 氧析出反应 3

1.3 锌-空气电池中空气电极 4

1.3.1空气电极的结构 4

1.3.2 空气电极催化剂研究现状及本课题的理论依据 5

1.3.4锌-空气电池催化剂亟待解决的问题 11

第二章 实验方案及实验方法 12

2.1 研究目的及内容 12

2.2实验试剂与仪器 13

2.2.1 实验原料和试剂 13

2.2.2 实验设备和仪器 13

2.3空气电极的制备 14

2.3.1 集流体的选择 14

2.3.2 防水透气层的制备 14

2.3.3 催化层的制备 14

2.3.4 空气电极的制备 14

2.4 锌-空气电池钙钛矿型催化剂的制备 16

2.4.1 LaMnO₃催化剂的工艺参数设计 16

2.4.2 LaMnO₃催化剂的制备工艺 17

2.4.3 La_xSr_1-xMnO₃催化剂的制备工艺 17

2.5钙钛矿型催化剂的结构及性能表征 18

2.5.1 X射线衍射分析 18

2.5.2 热分析 18

2.5.3 透射电子显微镜分析 19

2.5.4 催化剂粉体分散工艺 19

2.5.5 极化曲线测试 19

第三章 实验结果与讨论 21

3.1 钙钛矿型LaMnO₃催化剂制备工艺研究 21

3.1.1 煅烧温度对LaMnO₃的影响 21

3.1.2 分散剂对材料性能的影响 23

3.1.3 煅烧时间的影响 23

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