【作者】 梁明德；

【导师】 翟玉春； 徐景明；

【作者基本信息】 东北大学 ， 冶金物理化学， 2009， 博士

【摘要】 高温电解制氢(HTSE)可以利用先进核反应堆提供的工艺热和电能,在高温下将水蒸气高效电解为氢气和氧气,实现高达48～59%的热转化效率,是未来可能用于大规模制氢的方法之一。HTSE的核心装置是固体氧化物电解池(SOEC),原理上是目前研究较多的固体氧化物燃料电池(SOFC)的逆过程。但是从SOFC模式转变到SOEC模式后,由于工作环境和电极极化方向的改变,SOEC对材料和运行工艺都提出新的要求,直接将SOFC逆向运行不能得到性能优化的SOEC,开发适用于电解模式下的高效电解质和电极材料是SOEC技术实用化所需解决的一个关键问题。本论文主要的研究结果如下：1、氢电极预烧温度、YSZ电解质烧结温度和印刷厚度是影响YSZ电解质薄膜致密度的关键因素。经过1000℃预烧的氢电极机械强度更好,更有利于印刷操作。YSZ较适合的烧结温度范围为1350～1400℃,当烧结温度高于1450℃,SOEC的性能下降。当印刷层数达到4层(约10μm)时,可满足SOEC对YSZ电解质气密性的要求。在致密电解质上制备一层多孔的YSZ进行微结构改性,可有效增加电极的活性面积,提高电解性能。2、分别采用氨水沉淀法和尿素燃烧原位合成法成功制备了高性能的NiO-YSZ复合粉体,通过对两种工艺路线合成的粉体材料比较选用尿素燃烧原位合成法来制备NiO-YSZ目标粉体,并对其合成工艺条件进行了优化。梯度化设计后的氢电极制备的单体电解池的制氢性能明显高于非梯度化的SOEC。3、原位合成法制备的LSM-YSZ复合粉体在合成重现性、电解性能和运行的稳定性上均优于机械混合法制备的LSM-YSZ,更适合用来制备SOEC氧电极。LSM-YSZ氧电极在SOEC模式下的活化机理表明：阳极极化/电流能够将Mn离子还原,并使偏析于LSM表面的SrO进入到LSM的晶格内,使得LSM中产生氧空位,增加氧电极的反应活性位置,从而提高LSM-YSZ氧电极的性能。4、利用本论文所研究的制备工艺组装的单电解池表现了良好的电解性能,在以0.33 Acm-2恒流电解50 h的过程中,电解电压稳定在0.93～0.95 V, SOEC的性能未出现衰减,SOEC的产氢速率可高达138 Nmlcm-2h-1。研究还发现,电解温度的升高和氢电极进气中水蒸气含量的升高有利于电解反应的进行,适宜的水蒸气含量为70%～80%。Pt集流体中的Bi和Na等低熔点元素对SOEC微结构具有破坏作用,在改进集流体后,SOEC运行稳定。本文开发的电解质表面微结构改性技术和电极原位合成方法有利于SOEC电解性能和稳定性的提高,可为高温蒸汽电解制氢奠定基础。更多还原

【Abstract】 High temperature steam electrolysis (HTSE), which is the highly efficient electrolysis of steam at high temperature and utilizes the heat and electrical power supplied simultaneously by advanced nuclear reactor, provides a very promising way for the large-scale production of hydrogen in the future. The conversion efficiency of thermal energy to hydrogen in HTSE can be up to 48-59%. Solid oxide electrolysis cell (SOEC), a reverse reaction of solid oxide fuel cell (SOFC) developed vigorously worldwide in principle, is the key component of HTSE system. However, Operation in SOEC mode is fundamentally different from that in SOFC mode due to the obvious change in direction of the electrochemical reaction and various operating conditions. It is hard to get optimized performance of SOEC based on the direct reverse operation of SOFC. Therefore, SOEC puts forward new demands for materials and technology. And, it is of great importance to improve the performance of electrolyte and electrodes for the practicability of SOEC technology in the future. The main aims of this dissertation were the preparation and fabrication technique of SOEC components for the application of HTSE.1. Pre-sintering temperature of hydrogen electrode, sintering temperature of YSZ electrolyte and the thickness of electrolyte are the key factors to affect the density of the electrolyte film. When the pre-sintering temperature is over 1000℃, it is beneficial for the improvement of mechanical strength of the hydrogen electrode and in favor of the printing operation. The suitable sintering temperature of YSZ is between 1350℃and 1400℃. When the temperature is over 1450℃, the performance of SOEC will decrease quickly. And the more appropriate thickness of the electrolyte is about 10μm. The active electrode area and the electrolysis performance can be increased effectively by the microstructure modification of YSZ through the preparation of a layer porous YSZ on the surface of the dense electrolyte.2. NiO-YSZ composite powder was highly efficient synthesized via in situ urea combustion method and ammonia precipitation method, respectively. Through the comparative analysis of products, in situ urea combustion method was adopted as the preparation method in the research and the optimization of technological conditions for the synthesis was investigated. The hydrogen production performance of the single SOEC with optimized gradient hydrogen electrodes is obvious higher than that of cells with non-gradient hydrogen electrodes.3. The in-situ LSM-YSZ powder shows better reproducibility, electrolysis performance and stability than traditionally direct mixture LSM and YSZ oxygen electrode. A mechanism which involves the incorporation of SrO segregated on the surface into the LSM lattice and the generation of oxygen vacancies in the LSM electrode is proposed for the activation process with O2- oxidation on LSM electrodes.4. The electrochemical test of the single button cells assembly of the above self-prepared electrodes and electrolyte shows excellent electrolysis performance. The electrolysis voltage can be kept at 0.93-0.95 V with a hydrogen production rate up to 138 Nmlcm-2h-1 and no degradation for 50h at the current density of 0.33 Acm-2 Moreover, it is found that the increase of temperature and steam content are conducive to the electrolysis reaction. The suitable steam content is from 70% to 80%. Bi and Na elements with low melting point in the Pt collector can damage the microstructure of SOEC.In this paper, the R&D of microstructure modification technology on the surface of dense electrolyte and the novel in situ synthesis method of electrodes are beneficial for the improvement of the performance and stability of SOEC, which are the basis for the further application of HTSE technology.更多还原