【作者】 王文宝；

【导师】 马桂林；

【作者基本信息】 苏州大学 ， 无机化学， 2011， 博士

【摘要】 固体电解质是一类重要的功能材料。它们在燃料电池,化学传感器,氢、氧气的电解制备、分离和提纯,分子泵,氮的氧化物消除器,硫化氢消除器,有机物的催化氢化和脱氢,核聚变反应堆废气中的重氢、超重氢等氢的同位素气体的回收利用,常压合成氨等方面具有十分重要的应用价值和广阔的应用前景。传统的固体电解质材料Y稳定的氧化锆（YSZ）因其高的氧离子导电性及在氧化、还原性气氛中的化学稳定性而在电化学装置中得到普遍的应用。但是,由于以此为电解质的电化学装置工作温度高达800℃以上,这导致对连接材料、密封材料、电极材料的要求高、成本高,不同组分间易相互扩散、材料易老化、由于应力及相变等原因而导致材料易开裂、难密封等一系列严重问题,阻碍了其进一步商业化的发展。由于中温电化学装置能够兼有高温和低温电化学装置的许多优点:（1）较快的电极反应速度;（2）较高的CO等杂质容忍性能;（3）较好的密封材料及连接材料选择性;（4）较简单的电化学装置结构;（5）较容易的水、热管理等。多年来以SrCeO₃、BaCeO₃、BaZrO₃、LaGaO₃等为母体的ABO₃钙钛矿型陶瓷电解质材料由于其在中温（300―800℃）范围内良好的离子导电性而引起人们的极大关注。此类ABO₃钙钛矿型固体电解质材料的导电性及应用方面的研究对于完善中温燃料电池等电化学装置的性能十分重要,同时也具有非常重要的意义。基于以上情况,本论文主要对ABO₃钙钛矿型固体电解质在中温范围内的电性能及应用进行了研究。主要研究工作及结果如下:（1）本文第一章简要介绍一些典型的无机质子及氧离子导体,缺陷化学及离子传导机制,介绍钙钛矿型无机质子及氧离子导体的一些应用。（2）众所周知,掺杂的BaCeO₃基钙钛矿陶瓷具有最高的质子电导率。在众多稀土离子掺杂的BaCeO₃固体电解质陶瓷材料中Dy掺杂的BaCeO₃材料受到了一定的关注。而对Dy掺杂的BaCeO₃陶瓷材料在中温（300―600℃）范围内的质子导电性至今还未见报道。本论文第三章研究了Dy₂O₃掺杂的BaCeO₃陶瓷在中温下、还原性气氛中的离子导电性。利用微乳液方法成功地合成了Dy掺杂的BaCeO₃系列陶瓷样品前驱体,结合后续较低温度下的热处理成功地制备出致密、具有单一钙钛矿结构的BaCe_1-xDy_xO_3-α （x = 0.05, 0.10, 0.15, 0.20）陶瓷样品。利用同位素效应、氢浓差电池、电导率与氧分压的关系等多种电化学分析方法研究了陶瓷样品在300―600℃中温范围、还原性气氛中的导电性能。研究发现在中温、氢气气氛中陶瓷样品几乎是纯的离子导体,其中BaCe_0.85Dy_0.15O_3-α具有最高的离子电导率,其600℃的离子电导率为0.93×10^-2 S cm^-1;以BaCe_0.85Dy_0.15O_3-α陶瓷样品为固体电解质成功地进行了常压合成氨。在外加直流电为1.2mA、温度为530℃时合成氨产率达到3.5×10^-9 mol s^-1 cm^-2。这进一步证实了Dy掺杂BaCeO₃系列陶瓷样品具有良好的中温质子导电性。（3）1998年,希腊研究人员Marnellos和Stoukides以无机质子导体SrCe_0.95Yb_0.05O_3-α为电解质,以N₂和H₂为原料组装电解池反应器,成功地实现了常压合成氨。但如何进一步提高常压合成氨产率及电化学透过氢转化为氨的转化率是一个重要的研究课题。从工业化发展的角度看,固体电解质薄膜化是发展趋势。合成氨电解池的电解质薄膜化（数μm到数十μm）有利于降低电解质内阻及能耗、提高电流效率、合成氨产率及转化率。本文第四章提出了以阳极支撑型BaCe_0.85Y_0.15O_3-α（BCY15）陶瓷膜为电解质组装合成氨反应器的新发展方向。采用简易、低成本的浆料旋涂法制备了阳极支撑型的BCY15陶瓷膜,结合后续的热处理得到了致密、均一及厚度约为30μm的BCY15固体电解质薄膜。以Ni- BCY15 /BCY15/ Ba_0.5Sr_0.5Co_0.8Fe_0.2O₃?α多层部件为基础组装了中温常压合成氨反应器,并成功地进行了常压合成氨。微结构研究表明各电极功能层与电解质膜结合良好;各电极呈现多孔状结构,有利于气体扩散,增大三相反应界面。在外加电流为1.0mA、温度为530℃时合成氨产率达到4.1×10^-9 mol s^-1 cm^-2。这个结果几乎是我们以前利用同一电解质陶瓷片进行合成氨实验所得到结果(2.1×10^-9 mol s^-1 cm^-2)的两倍。这表明将膜反应器应用于合成氨有助于氨产率及电流效率的提高。阻抗谱研究表明:随着温度的升高,电极极化阻抗和电解质阻抗明显减小,膜反应器的总阻抗明显减小,这是电流效率及氨产率得以提高的重要原因。（4）虽然BaCeO₃基固体电解质材料具有良好的离子导电性。但是固体电解质应用于固体氧化物燃料电池等电化学装置时其必须具备高化学稳定性和高机械强度。虽然稀土掺杂的BaCeO₃被认为具有最高的质子电导率,但是它们在含水及二氧化碳气氛中的化学稳定性差,而掺杂的BaZrO₃虽在含水及二氧化碳的气氛中具有很好的化学稳定性,但其烧结性能差,且晶界电阻大,电导率低。近来,综合两种材料的优缺点,铈酸钡和锆酸钡固溶体的研究受到了研究工作者的广泛关注。第五章我们利用硝酸盐—柠檬酸法合成的BaCe_0.75Zr_0.1Y_0.15O_3-α粉体制备浆料并结合简易的浆料旋涂工艺成功地制备出非常致密、均一、厚度约为25μm的阳极支撑型BaCe_0.75Zr_0.1Y_0.15O_3-α电解质陶瓷膜,并将其应用于中温固体氧化物燃料电池。组装成的BaCe_0.75Zr_0.1Y_0.15O_3-α陶瓷膜燃料电池显示出良好的输出性能,在650℃、700℃和800℃下的最大输出功率密度分别达到150 mW cm^-2、206 mW cm^-2及349mW cm^-2。微结构分析表明,未添加造孔剂的阳极支撑体孔隙率低,影响了燃料电池性能。进一步优化工艺,特别是阳极支撑体的工艺,可使中温SOFC的性能得到进一步提高。（5）SrO和MgO掺杂的LaGaO₃陶瓷具有优良的氧离子导电性能,它在800℃时的氧离子电导率比钇稳定化二氧化锆（YSZ）几乎高出一个数量级,且在很宽的氧分压范围(1—10^-20atm)内几乎是纯的氧离子导体。最近我们课题组发现La_0.9Sr_0.1Ga_0.8Mg_0.2O_3-α（LSGM）在600—1000℃、氢气气氛中具有很好的质子导电性。此材料同时又具有较好的化学和机械稳定性,因而被公认为最有希望的中温固体氧化物燃料电池的候选电解质材料之一。多年来将LSGM材料薄膜化应用于SOFC的报道很多,然而利用简易浆料旋涂法制备LSGM电解质薄膜的研究还未见报道。第六章我们以共沉淀法及硝酸盐—柠檬酸法分别制备出NiO和Ce_0.8Gd_0.2O_3-α（GDC）纳米粉体应用于阳极支撑体及阻隔层。结合简易、低成本的浆料旋涂工艺在具有GDC阻隔层的阳极支撑体上制备出高质量的LSGM电解质薄膜。经后续的热处理（1300℃,5h）后,获得了致密、均一及厚度约为50μm的LSGM固体电解质薄膜。以多孔性Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-β（BSCF）为阴极,Ag-Pd为集电体,分别以氢气和空气为阳、阴极气体,组装成的La_0.9Sr_0.1Ga_0.8Mg_0.2O_3-δ陶瓷膜燃料电池在600℃和700℃下的输出功率密度分别达到257 mW cm^-2和760mW cm^-2。阻抗谱研究表明:在中温（400―700℃）下,随着温度的升高,电极极化和电解质阻抗明显减小。陶瓷膜燃料电池具有相当低的极化阻抗（700℃、0.025Ωcm²）,且电极极化阻抗始终小于电解质阻抗。这表明优化的电极微结构是燃料电池取得优良性能的重要因素。（6）第七章对本论文的工作创新点进行了概括,对本研究中的不足进行了简要分析,对以后的工作进行了展望。更多还原

【Abstract】 Solid electrolyte materials are a kind of important functional materials and have attracted much attention because of their potential application values and wide application prospects in solid oxide fuel cells （SOFCs）, gas sensors, steam electrolyzes, separation and purification of hydrogen, hydrogenation and dehydrogenation of some organic compounds and ammonia synthesis at atmospheric pressure, etc.The traditional electrochemical devices using Y₂O₃ stabilized ZrO₂ （YSZ） as electrolytes, due to its good chemical stability, high-mechanical stability and pure ionic conduction, require operating temperatures around 1000℃. However, relatively high operating temperature can result in not only high fabrication cost for electrochemical device systems, but also complex material problems including electrode sintering, interfacial diffusion between electrolyte and electrodes, and mechanical stress due to the different thermal expansion coefficients. Therefore, more recently, ABO₃ perovskite- type intermediate-temperature solid electrolyte materials such as doped SrCeO₃、BaCeO₃、BaZrO₃, LaGaO₃, etc. have attracted much attention because of their well conduction behaviors. Compared to low- or high-temperature electrochemical devices, intermediate-temperature electrochemical devices have many advantages: （1） faster speed of electrode reactions; （2） higher CO and other impurities’tolerance performance; （3） more easily electivity for sealing materials and connection materials; （4） simple structure of the electrochemical device; （5） more easily management in water, thermal cycle. Therefore, studying the details of intermediate-temperature conduction behaviors of ABO₃ perovskite- type electrolytes themselves and their application may be of significant for the commercial development of electrochemical devices.Therefore, in the thesis we focus on conduction behaviors and some applications of ABO₃ （A = La, Ba; B = Ga, Ce） perovskite-type solid electrolytes at intermediate temperature. Main works and results in this paper are as follows:（1） In chapter 1, we review the definition of solid electrolyte materials and their application prospects, and introduce briefly the typical ABO₃ perovskite- type electrolyte materials. In addition, we also propose our main research work.（2） It is generally believed that doped BaCeO₃-based ceramic materials show the highest proton conductivities. However, to the best of our knowledge, related studies on proton conduction in Dy-doped BaCeO₃ at the intermediate temperature range of 300 - 600℃have not been reported until now. In chapter 3, ionic conduction at the intermediate temperature range, especially ionic conduction under reducing atmosphere in Dy₂O₃ doped BaCeO₃ ceramics was investigated. The precursor powders of BaCe_1-xDy_xO_3-α（x = 0.05, 0.10, 0.15, 0.20） ceramics were prepared via a microemulsion process. It was shown from SEM images that all the ceramic samples were quite dense. Structure investigation on the powder X-ray diffraction patterns showed that the ceramic samples have single perovskite structures. Rietveld analysis suggested that there was a possible orthorhombic distortion of structure with increasing Dy concentration. The proton conduction in these ceramics at intermediate temperature range of 300 - 600℃was investigated. It was found from the isotope effect on conductivity that the samples had obvious proton conduction in hydrogen-containing atmosphere. The highest ionic conductivity 0.93×10^-2 S·cm^-1 was observed for x = 0.15 in wet hydrogen atmosphere （pH₂O = 0.023 atm） at 600℃. Ammonia was synthesized successfully in an electrolytic cell using BaCe_0.85Dy_0.15O_3-α ceramic as an electrolyte at atmospheric pressure and the maximum rate of NH₃ formation was 3.5×10^-9 mol/s·cm² at 530℃with an imposed direct current of 1.2 mA, which confirmed that Dy - doped BaCeO₃ ceramic electrolyte has excellent proton conduction at intermediate temperature.（3） In 1998, ammonia synthesis at atmospheric pressure has been realized successfully in an electrolytic cell reactor using a high temperature proton conductor SrCe_0.95Yb_0.05O_3-α. The process provides an alternative route that permits operation at atmospheric pressure and avoids the problem of thermodynamic restrictions imposed on the conventional Haber catalytic reactors. But how to further improve the ammonia formation rate and hydrogen conversion rate are two important research topics. Therefore, from a practical application point of view, developing thin solid electrolyte membrane for various electrochemical devices is a trend. A electrolytic cell using electrolyte membrane （fewμm to tens ofμm） for ammonia formation will be help to reduce the electrolyte resistance, improve ammonia formation and hydrogen conversion rates. The chapter 4 proposes a new research direction of ammonia synthesis reactor at atmospheric pressure with a thin solid electrolyte BaCe_0.85Y_0.15O_3-α membrane. A tri-layer membrane reactor for ammonia synthesis at atmospheric pressure comprised with a thin proton conduction electrolyte （BCY15） membrane and two functional electrode layers （Ni-BCY15 and BSCF） was assembled successfully. A dense, uniform and crack-free thin proton conduction electrolyte BCY15 membrane prepared by a modified spin coating was obtained after sintering at 1400℃for 5h. AC impedance spectra showed that the membrane reactor had a relatively small resistance. The polarization resistance and the electrolyte resistance increased with the decrease of temperature. The present study demonstrated that higher rate of ammonia rate can be achieved in a reactor with thin solid electrolyte BCY15 membrane. Compared with our prior result, the ammonia formation rate was improved obviously and reached 4.1×10^-9 mol s^-1 cm^-2 with an applied current 1mA at 530℃. The current efficiency of the thin membrane reactor had also been improved obviously.（4） The BaCeO₃-base perovskite materials exhibit fairly high ionic conductivity at intermediate temperature in humid reducing atmosphere. However, these oxides display rather poor chemical stability in atmosphere containing CO₂ and H₂O. On the orther hand, BaZrO₃-base perovskite materials have rather good chemical stability in atmosphere containing CO₂ and H₂O. Therefore preparing the solid solution of BaCeO₃ and BaZrO₃ combined the high ionic conduction of barium cerate with the good chemical stability of barium zirconate has been a research foucs. In order to develop a cost-effective and simple process to fabricate intermediate temperature solid oxide fuel cell, a simple and cost-effective dense pin-coating method was developed to prepare BaCe_0.75Zr_0.1Y_0.15O_3-α electrolyte membrane （25μm in thickness） on porous anode support. A tri-layer NiO- BaCe_0.75Zr_0.1Y_0.15O_3-α / BaCe_0.75Zr_0.1Y_0.15O_3-α /BSCF single cell was assembled and tested from 650-800℃with humidified H₂ as the fuel and ambient air as the oxidant. The open-circuit voltage （OCV ）values reached 0.94V at 800℃, and 0. 99V at 650℃,respectively. The maximum power densities were 349 mWcm^-2 at 800℃and 206 mWcm^-2 at 700℃, respectively. Microstructure analysis showed that the anode support without pore former had low porosity, which was responsible for the low fuel cell performance. Further optimizing process, especially the technical of preparing anode supports, can further improve the performance of intermediate-temperature SOFC.（5） Strontiumm- and mmagnesium-doped lanthanum gallate （LSGM） perovskite-type material is often regarded as a promising family of alternative electrolyte for IT-SOFCs due to their superior oxygen ionic （almost one order of magnitude larger than that of YSZ） and protonic conduction, good chemical stability and especially, high ionic transference number in the intermediate temperature range. Recently our research group discovered that La_0.9Sr_0.1Ga_0.8Mg_0.2O₃–α? ? possesses excellent proton conduction in hydrogen atmosphere at 600-1000℃. Recently, considerable research work has been devoted to developing thin LSGM membrane fuel cell with high output power density capable of operating in the intermediate temperature range. However, to date there is little information available on LSGM membrane prepared via spin-coating process. In chapter 6, a simple and cost-effective spin coating process was applied to deposit LSGM membrane on porous NiO-GDC anode support with a GDC barrier layer. After co-sintering at relatively low temperature 1300℃for 5 h, a dense and uniform electrolyte membrane with the thickness of ca. 50μm was obtained. An anode-support LSGM membrane fuel cell with BSCF cathode was assembled and tested from 600℃to 700℃using humidified hydrogen as the fuel and ambient air as the oxidant. The OCV values reached 1.00V at 700℃, and 1.02 V at 600℃,respectively. The maximum power densities were 760 mW cm^-2 at 700℃and 257 mW cm^-2 at 600℃, respectively. In addition, the AC impedance analysis of the single cell demonstrated desirable low electrode polarizations. In conclusion, the spin coating process has been confirmed to be an effective method to prepare thin LSGM electrolyte membrane for IT-SOFCs.（6） In chapter 7, we summarized the work and highlights in the dissertation. We also briefly analyzed the lack of work and further work in the future.更多还原