碱土与过渡金属掺杂的双钙钛矿结构阴极材料及其性能

发布时间：2018-05-23 12:00

本文选题：固体氧化物燃料电池 + 双钙钛矿　；参考：《吉林大学》2016年博士论文

【摘要】：固体氧化物燃料电池(SOFC)是一种能量转换效率高、环境污染少的新型能源技术。近年来,工作温度在600-800°C的中温固体氧化物燃料电池(IT-SOFC)逐渐受到人们的关注。相对于传统SOFC,更低的工作温度,使得IT-SOFC在电池材料的选择范围、电池工作的稳定性以及电池制造成本等方面具有明显的优势。由于传统的SOFC阴极材料不适宜在中温范围(600-800°C)内工作,因此开发新型IT-SOFC阴极材料对于促进SOFC技术的发展,具有非常重要的意义。本文以备受关注的AA'B_2O_(5+δ)双钙钛矿阴极材料LnBa Co_2O_(5+δ)(Ln BCO)为基础,通过不同的掺杂策略,对其电导率、热膨胀以及电化学催化性能进行优化,以期开发出性能更加优异的IT-SOFC阴极材料。我们用固相法合成了A位Ca~(2+)掺杂的Pr_(1-x)Ca_xBa Co_2O_(5+δ)(x=0.10-0.40;PCBCO)阴极材料。发现PCBCO(x=0.10,0.20)样品形成了单相的四方结构双钙钛矿氧化物;而PCBCO(x=0.30,0.40)样品则有不同程度的杂质出现。PCBCO阴极与SDC电解质在950°C煅烧10 h的条件下呈现出良好的化学兼容性。在Ca~(2+)部分替代Pr~(3+)的PCBCO样品中,由于Pr~(3+)位离子平均氧化态降低,导致样品氧含量随Ca的掺杂而降低。随着Ca掺杂量的增加,样品中更多的Co~(3+)被稳定在中自旋态,致使PCBCO样品的热膨胀系数(TEC)呈下降趋势。在100-800°C温度范围内x=0.10-0.30样品的平均TEC值分别为22.2×10~(-6)、20.0×10~(-6)和19.1×10~(-6) K~(-1),均小于未掺杂的Pr BCO阴极材料在同样温度范围内的TEC。在PCBCO中引入SDC电解质材料可以进一步降低材料的TEC。PCBCO(x=0.10)-SDCy(y=40 wt.%)复合阴极在100-800°C温度范围内的平均TEC值下降到17.4×10~(-6) K~(-1)。PCBCO(x=0.10-0.30)样品在300-850°C温度范围内具有金属性导电行为,电导率大于300 S cm~(-1),比Pr BCO的电导率有所降低。这归因于PCBCO中较低的氧含量导致载流子(Co~(4+))浓度降低。PCBCO(x=0.10)-SDC复合阴极的电导率随SDC含量增加逐渐下降,但在300-850°C温度范围内电导率仍然大于100 S cm~(-1)。PCBCO(x=0.10-0.30)样品的ASR随Ca掺杂量的增加而增大,700°C时PCBCO阴极在SDC电解质上的ASR分别为0.081、0.082和0.089Ωcm~2,高于Pr BCO阴极材料的ASR值。导致PCBCO(x=0.10-0.30)阴极ASR增大的主要原因是:Ca的掺杂在样品中引入了过量的氧空位,导致缺陷聚集,氧离子传导性能下降。SDC的引入有助于改善阴极材料的电化学性能,最佳比例的PCBCO(x=0.10-0.30)-SDCy(y=20 wt.%)复合阴极在700°C时的ASR值分别为0.060、0.071和0.074Ωcm~2。单电池输出性能研究表明,800°C时,以PCBCO(x=0.10-0.30)为阴极的单电池,最大功率密度分别为646.5、636.8和620.6 m W cm~(-2);以PCBCO(x=0.10-0.30)-SDCy(y=20 wt.%)复合材料为阴极的单电池输出性能进一步改善,800°C时最大功率密度分别达到了684.7、660.2和644.3 m W cm~(-2)。上述研究结果表明,Ca~(2+)在A位掺杂可降低PCBCO材料的热膨胀系数,同时也降低了稀土材料的成本;PCBCO(x=0.10-0.30)阴极和PCBCO(x=0.10-0.30)-SDCy(y=20 wt.%)复合阴极均表现出良好的电化学性能,是很有发展前途的潜在IT-SOFC阴极材料。A位Ca~(2+)掺杂的PCBCO阴极材料在热膨胀性能方面得到了一定程度的改善,但电化学性能却随着Ca的引入而有所下降。为了提高Pr BCO的电化学性能,我们用固相法合成了A'位Ca掺杂的PrBa_(1-x)Ca_xCo_2O_(5+δ)(x=0.05-0.15,PBCCO)阴极材料。发现PBCCO样品为具有四方结构的双钙钛矿型氧化物,与SDC电解质在950°C煅烧10 h的条件下具有良好的化学兼容性。随着Ca的掺杂,具有自旋态转变特性的Co~(3+)离子所占比例减少,使得PBCCO样品从x=0.05到0.15,TEC呈下降趋势,在100-800°C温度范围内,样品的平均TEC值分别为22.6×10~(-6)、21.6×10~(-6)和20.9×10~(-6) K~(-1),相比于未掺杂的Pr BCO,TEC有所下降。在300-850°C温度范围内,PBCCO样品具有金属性导电行为,电导率大于620 S cm~(-1)。从x=0.05到0.15,PBCCO样品中载流子(Co~(4+))浓度逐渐升高,使得电导率呈上升趋势。随着Ca的掺杂,PBCCO样品中氧空位逐渐减少,氧离子传导性能下降,导致PBCCO阴极材料在SDC电解质上的ASR呈上升趋势,700°C时PBCCO阴极在SDC电解质上的ASR值分别为0.047、0.050和0.052Ωcm~2。相比于未掺杂的Pr BCO,PBCCO的ASR明显降低,这得益于PBCCO系列样品较高的电导率和较低的TEC。单电池输出性能测试表明,800°C时,以PBCCO(x=0.05-0.15)为阴极的单电池,最大功率密度分别为669.7、634.1和577.4 m W cm~(-2)。上述研究结果表明,Ca~(2+)离子在A'位置掺杂,可降低PBCCO材料的热膨胀系数,提高电学和电化学性能;PBCCO(x=0.05-0.15)阴极材料具有优秀的电化学催化性能,是很有应用前景的IT-SOFC阴极材料。Ln BCO基阴极材料由于其所含的Co~(3+)离子随着温度的升高会出现由低自旋态向高自旋态的转变,导致材料具有很高的TEC。通过前面提到的不同掺杂策略可使其热膨胀性能获得一定改善,但仍然无法达到与电解质材料十分匹配的热膨胀系数。为此,我们合成了不含Co元素的Sm Ba Fe Ni O5+δ(SBFN)双钙钛矿阴极材料。研究发现,SBFN为具有四方结构的双钙钛矿氧化物,与SDC电解质在950°C煅烧10 h的条件下化学兼容性良好。SBFN样品在30-900°C温度范围内的平均TEC为14.1×10~(-6) K~(-1),远低于含Co的Sm BCO材料。SBFN较低的TEC缘于以Fe和Ni完全取代了Co元素,材料的热膨胀性能不再受Co~(3+)离子自旋态转变的影响。此外,Fe-O键的结合能比Co-O键的结合能更高,也有助于减弱晶格膨胀,因此降低了TEC。在SBFN中引入SDC电解质材料所构成的复合阴极,其热膨胀匹配性得到了进一步改善。SBFN-SDCx(x=5,10,15 wt.%)复合阴极的TEC分别为13.8×10~(-6)、13.4×10~(-6)和12.0×10~(-6) K~(-1)。电导率研究表明,SBFN样品在300-425°C温度范围内呈半导体导电特性;而在425-850°C温度范围内呈金属导电特性,在425°C时具有最大电导率,为48 S cm~(-1)。700°C时,SBFN在SDC电解质上的ASR值为0.386Ωcm~2。在SBFN中引入SDC电解质可以提高阴极的电化学性能,700°C时SBFN-SDC10阴极的ASR值为0.224Ωcm~2,相对于单相的SBFN阴极,极化阻抗降低了42%。800°C时,以SBFN和SBFN-SDC10为阴极的单电池,最大功率密度分别为367.6 m W cm~(-2)和507.8m W cm~(-2)。以上研究结果表明,用Fe和Ni完全置换Co,可明显地降低无钴阴极材料SBFN的热膨胀系数;经过性能优化,SBFN-SDC10复合阴极材料表现出较好的阴极性能,可作为IT-SOFC的候选阴极材料。我们采用三种不同的掺杂策略,研究了降低Co基双钙钛矿阴极材料Ln BCO热膨胀系数的方法,为探寻Ln BCO双钙钛矿阴极材料的改性与优化提供了有益的参考和借鉴。
[Abstract]:Solid oxide fuel cell (SOFC) is a new energy technology with high energy conversion efficiency and less environmental pollution. In recent years, the medium temperature solid oxide fuel cell (IT-SOFC) at the working temperature of 600-800 C has been gradually paid attention to. Compared with the traditional SOFC, the lower working temperature makes IT-SOFC in the selection range of the battery material. The stability of the pool work and the cost of battery manufacturing have obvious advantages. Since the traditional SOFC cathode materials are not suitable for the medium temperature range (600-800 C), it is very important to develop a new type of IT-SOFC cathode material for the development of SOFC technology. This paper is a highly concerned AA'B_2O_ (5+ delta) double calcium titanium. Based on the cathode material LnBa Co_2O_ (5+ delta) (Ln BCO), the conductivity, thermal expansion and electrochemical catalytic properties of the cathode materials were optimized by different doping strategies, in order to develop a IT-SOFC cathode material with better performance. We synthesized A bit Ca~ (2+) doped Pr_ (1-x) Ca_xBa cathode (A) cathode by solid phase method. Material. It was found that PCBCO (x=0.10,0.20) samples formed a single phase tetragonal perovskite oxide, while PCBCO (x=0.30,0.40) samples showed a good chemical compatibility with.PCBCO cathode and SDC electrolyte at 950 degree C calcined 10 h. The average oxidation state of the + + ions is reduced and the oxygen content of the sample decreases with the doping of Ca. With the increase of Ca doping, more Co~ (3+) in the sample is stabilized in the middle spin state, resulting in the decrease of the thermal expansion coefficient (TEC) of the PCBCO samples. The average TEC value of x=0.10-0.30 samples in the range of 100-800 degree C is 22.2 x 10~ (-6), 20, respectively. X 10~ (-6) and 19.1 x 10~ (-6) K~ (-1) are less than the undoped Pr BCO cathode materials in the same temperature range, and the introduction of SDC electrolyte in PCBCO can further reduce the average value of the material in the range of 100-800 degree temperature. 0.30) in the range of 300-850 C temperature, the sample has metallic conduction behavior, the conductivity is greater than 300 S cm~ (-1), and the conductivity of Pr BCO is lower than that of Pr BCO. This is attributed to the lower oxygen content in PCBCO which leads to the decrease of the carrier (Co~ (4+)) concentration of.PCBCO (x=0.10) and the conductivity of the -SDC compound cathode gradually decreases with the increase of the content, but at 300-850 degree temperature. The range of electrical conductivity is still greater than 100 S cm~ (-1).PCBCO (x=0.10-0.30).PCBCO (x=0.10-0.30) sample increases with the increase of Ca doping. The ASR of PCBCO cathode on SDC electrolyte at 700 degree C is respectively 0.081,0.082 and 0.089 Omega, which is higher than that of the cathode material. The introduction of excessive oxygen vacancies leads to defects aggregation, and the introduction of oxygen ion conductivity decrease.SDC is helpful to improve the electrochemical performance of cathode materials. The optimum proportion of the PCBCO (x=0.10-0.30) -SDCy (y=20 wt.%) composite cathode at 700 degree C is respectively 0.060,0.071 and 0.074 Omega cm~2. single battery output performance studies show that the 800 degree C, The maximum power density of the single cell with PCBCO (x=0.10-0.30) as the cathode is 646.5636.8 and 620.6 m W cm~ (-2), and the output performance of the single cell with PCBCO (x=0.10-0.30) -SDCy (y=20 wt.%) composite as the cathode is further improved. The maximum power density at 800 degrees is reached and 644.3 respectively. The above results show that The doping of Ca~ (2+) in A can reduce the thermal expansion coefficient of the PCBCO material and reduce the cost of the rare earth materials. The PCBCO (x=0.10-0.30) cathode and the PCBCO (x=0.10-0.30) -SDCy (y=20 wt.%) composite cathode both show good electrochemical performance, and are promising cathode materials of potential IT-SOFC cathode materials in the future. The properties of thermal expansion were improved to a certain extent, but the electrochemical performance decreased with the introduction of Ca. In order to improve the electrochemical performance of Pr BCO, we synthesized A'Ca doped PrBa_ (1-x) Ca_xCo_2O_ (5+ delta) (5+ delta) (x=0.05-0.15, PBCCO) cathode material by solid phase method. It was found that the PBCCO samples were double perovskite with the Quartet structure. The type oxides have good chemical compatibility with the SDC electrolyte at 950 C calcined at 10 h. With the doping of Ca, the proportion of Co~ (3+) ions with the spin state transformation decreases, making the PBCCO samples from x=0.05 to 0.15 and TEC decreasing. The average TEC value of the sample is 22.6 * 10~ (22.6), 21., respectively, within the range of 100-800 degree C. 6 * 10~ (-6) and 20.9 x 10~ (-6) K~ (-1), compared to the undoped Pr BCO, the TEC decreased. In the temperature range of 300-850 degree C, the PBCCO sample has a metallic conduction behavior, and the conductivity is greater than 620 S. The oxygen vacancy in the sample decreases gradually and the conductivity of oxygen ion decreases. The ASR of the PBCCO cathode material on the SDC electrolyte increases. The ASR value of the PBCCO cathode on the SDC electrolyte is 0.047,0.050 and 0.052 Omega cm~2. at 700 degree C, respectively, compared to the BCO Pr BCO, which is due to the higher electricity of the series of samples. The conductivity and low TEC. single cell output performance test showed that the maximum power density of the single cell with PBCCO (x=0.05-0.15) as the cathode at 800 C was 669.7634.1 and 577.4 m W cm~ (-2) respectively. The results showed that the doping of Ca~ (2+) ions in the A'position could reduce the thermal expansion coefficient of the material and improve the electrical and electrochemical properties. (x=0.05-0.15) the cathode material has excellent electrochemical catalytic performance. It is a promising cathode material for IT-SOFC cathode material.Ln BCO based cathode material, because of its Co~ (3+) ions as the temperature increases with the temperature, the transition from low spin to high spin will result in the material with a very high TEC. through the different doping strategies mentioned earlier. It can improve the thermal expansion performance, but still can not reach the thermal expansion coefficient that matches the electrolyte material. Therefore, we synthesized the Sm Ba Fe Ni O5+ Delta (SBFN) Double Perovskite Cathode material without Co elements. It was found that SBFN was a tetragonal perovskite oxide with a quartet structure, and the SDC electrolyte was calcined at 950 degree C in 10 h. Under the conditions of good chemical compatibility, the average TEC of.SBFN samples in the temperature range of 30-900 C is 14.1 x 10~ (-6) K~ (-1), which is far lower than the Sm BCO containing Co. The TEC is due to the replacement of the element, and the thermal expansion of the material is no longer influenced by the spin state transformation of the ions. The bonding energy of the bond is higher and helps to weaken the lattice expansion, thus reducing the TEC. composite cathode made by the introduction of the SDC electrolyte in SBFN. The thermal expansion matching has been further improved by the TEC of the.SBFN-SDCx (x=5,10,15 wt.%) composite cathode, 13.8 x 10~ (-6), 13.4 x 10~ (-6) and 12 * 10~. It is clear that the SBFN sample has the conductivity of semiconductor in the temperature range of 300-425 C; the conductivity of the metal is in the range of 425-850 degree C, and the maximum conductivity at 425 C. When it is 48 S cm~ (-1).700 [C], the ASR value of SBFN on the SDC electrolyte is 0.386 Omega, which can improve the electrochemical performance of the cathode, 700 degrees. The ASR value of the SBFN-SDC10 cathode is 0.224 Omega cm~2. Relative to the single phase SBFN cathode, the polarization impedance reduces the 42%.800 degree C, the single battery with SBFN and SBFN-SDC10 as the cathode, the maximum power density is 367.6 m W cm~, respectively. The thermal expansion coefficient of SBFN has been optimized. The SBFN-SDC10 composite cathode material shows good cathodic properties and can be used as the candidate cathode material for IT-SOFC. We have studied the method of reducing the Ln BCO thermal expansion coefficient of the Co Based Double Perovskite Cathode material by three different doping strategies, in order to explore the modification of the Ln BCO Double Perovskite Cathode material. It provides useful reference and reference for nature and optimization.
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TM911.4

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