尖晶石型锂空气电池电化学催化剂的制备及其性能研究
发布时间：2018-08-31 10:00
【摘要】：当前世界范围内正在经历新型能源体系变革,其主要内容是将新型可再生能源取代以化石能源为基础的能源体系, 实现由不可持续的现代工业文明向未来可持续的生态文明过渡,最终实现人类社会与地球生物圈循环规律有机融合。在所有开发的新型储能设备中具有高理论能量密度的锂空气电池,引起了人们的广泛关注。但是在锂空气电池运行中阴极氧气还原反应(ORR)动力学缓慢,会造成过电势损失,导致电池的实际能量密度与理论密度相差大,循环寿命短。研究发现通过使用催化剂可以降低反应活化能,减小电化学极化程度,进而提高锂空气电池的实际能量密度。在现在已知的催化剂中贵金属有很好的催化活性,特别是Pt类催化剂,但是由于贵金属资源匮乏、价格昂贵,阻碍了其在电化学催化中的广泛应用。所以研发具有高催化活性的非贵金属催化剂是推动锂空气电池商业化的关键。本论文选择化学稳定性好、价格便宜同时具有较高催化活性的尖晶石氧化物作为研究对象,使用酵母细胞和细菌纤维素作为模板和碳源,制备具有高催化活性和催化稳定性的CoFe2O4和碳复合催化剂,另外使用Li+离子和Mn2+离子分别作为杂质离子对NiCo2O4进行掺杂,提高其催化活性。研究的主要内容和取得的结果如下：(1)使用酵母细胞作碳源,通过化学沉淀法制备具有介孔结构的CoFe2O4/Co/C复合催化剂。通过调节酵母悬浮液的浓度,制得具有不同电化学催化性能的复合产物。当酵母悬浮液浓度为10 g L-1时,制得的复合产物CFO/Co/BC-2比表面积可以达到92.76 m2 g-1,在碱性条件下具有很好的催化活性和催化稳定性。在ORR催化过程中,CFO/Co/BC-2的起始电位仅为-0.176 V,极限电流密度可以达到7.25 mA cm-2。在氧气析出反应(OER)催化过程中其氧气析出起始电位为0.58 V,当电压为1 V时电流密度达到26.48 mA cm-2。当CFO/Co/BC-2在-0.35 V下经过86377 s连续工作后,其ORR电流密度仅降低了20.5%,在0.8 V下经过同样的工作时间后,其OER电流密度减小7.9%。(2)使用酵母细胞作碳源和模板,通过化学沉淀和冷冻干燥法制得直径为1-2.5μrn的CoFe2O4/C复合微球。复合材料中的C是酵母细胞碳化后生成的N和P掺杂的无定型碳,它本身就有很好的电化学催化活性,同时CoFe2O4和C之间的耦合作用会提高催化活性,所以在碱性条件下CoFe2O4/C复合微球有很好的催化活性和催化稳定性。在ORR催化过程中,CoFe2O4/C复合微球的氧气还原起始电位仅为-0.14 V。在OER催化过程中,其氧气析出起始电位为0.46 V,在电压为0.8 V时电流密度达到17.7 mA cm-2。当CoFe2O4/C复合微球在-0.35 V下经过43000 s连续工作后,其ORR电流密度仅降低了15.1%,在0.8 V下经过同样的工作时间后,其OER电流密度减小1.4%。(3)使用酵母细胞作模板,通过简单的两步煅烧法制得直径为1-2.5 μm的CoFe2O4空心微球。在ORR催化过程中,CoFe2O4空心微球的氧气还原起始电位为-0.29 V。在OER催化过程中,CoFe2O4空心微球的氧气析出起始电位比无规则形貌CoFe2O4小50 mV,在电压为1 V时电流密度达到45 mA cm-2。当CoFe2O4空心微球在-0.3 V下连续工作44000 s后,其ORR电流密度减小了16.4%,在0.8 V下经过相同的工作时间后,其OER电流密度降低了5.6%。(4)使用细菌纤维素作模板和碳源,通过水热法制得具有三维网状结构的CoFe2O4/C复合催化剂。在ORR催化过程中,CoFe2O4/C的氧气还原起始电位仅为-0.09 V,极限电流密度达到5.41 mA cm-2。在OER催化过程中,其氧气析出起始电压为0.58 V,在电压为1 V时电流密度达到23.02 mA cm-2。当CoFe2O4/C复合催化剂在-0.3 V下连续工作35000 s后,其ORR电流密度减小3.7%,在0.8 V下经过相同的工作时间后,其OER电流密度减小5.8%。(5)通过水热法制备Li+掺杂的LixNiCo2-xO4,调节Li+离子的掺杂量,当x=0.5时Li0.5NiCo1.5O4的ORR起始电位为-0.176 V,中间产物产率小于1%,电子转移数在3.97-4之间。同样通过水热法制备Mn2+掺杂的MnxNi1-xCo2O4,当x=0.2时Mn0.2Ni0.8Co2O4的ORR起始电位为-0.13 V,中间产物产率小于1.5%,电子转移数在3.96-4之间。
[Abstract]:Nowadays, the world is experiencing the reform of new energy system. Its main content is to replace fossil-based energy system with new renewable energy, to realize the transition from unsustainable modern industrial civilization to sustainable ecological civilization in the future, and finally to realize the organic integration of human society and the law of the Earth's biosphere cycle. Lithium-air batteries with high theoretical energy density have attracted extensive attention in all new energy storage devices developed. However, the slow kinetics of cathode oxygen reduction reaction (ORR) in the operation of lithium-air batteries will cause overpotential loss, resulting in a large difference between the actual and theoretical energy density and short cycle life. Nowadays, noble metals have good catalytic activity, especially Pt-type catalysts. However, due to the scarcity of precious metal resources and high price, it is difficult to use them in electrochemical catalysis. Therefore, the research and development of non-noble metal catalysts with high catalytic activity is the key to promote the commercialization of lithium-air batteries. In this paper, spinel oxides with good chemical stability, low price and high catalytic activity were selected as the research object, and yeast cells and bacterial cellulose were used as templates and carbon sources to prepare lithium-air batteries. C oFe2O4 and carbon composite catalysts with high catalytic activity and catalytic stability were doped with Li+ and Mn2+ as impurity ions respectively to improve the catalytic activity of NiCo2O4. The main contents and results were as follows: (1) Mesoporous C was prepared by chemical precipitation method using yeast cells as carbon source. OFe2O4/Co/C composite catalysts. Composite products with different electrochemical catalytic properties were prepared by adjusting the concentration of yeast suspension. When the concentration of yeast suspension was 10 g L-1, the specific surface area of the composite product CFO/Co/BC-2 could reach 92.76 M 2 g-1. It had good catalytic activity and catalytic stability under alkaline conditions. In the catalytic process, the initial potential of CFO/Co/BC-2 is - 0.176 V and the limiting current density is 7.25 mA cm-2. In the process of oxygen evolution reaction (OER), the initial potential of oxygen evolution is 0.58 V, and the current density is 26.48 mA cm-2 when the voltage is 1 V. (2) C oFe2O4/C composite microspheres with a diameter of 1-2.5 microrn were prepared by chemical precipitation and freeze-drying using yeast cells as carbon source and template. The C in the composite was the amorphous carbon doped with N and P produced by carbonization of yeast cells. CoFe2O4/C composite microspheres have good catalytic activity and stability under alkaline conditions. In ORR process, the initial potential of oxygen reduction of CoFe2O4/C composite microspheres is only - 0.14 V. In OER catalytic process, the initial potential of oxygen reduction of CoFe2O4/C composite microspheres is only - 0.14 V. The ORR current density of CoFe2O4/C composite microspheres decreased by 15.1% after 43 000 s continuous operation at - 0.35 V, and decreased by 1.4% after the same working time at 0.8 V. CoFe2O4 hollow microspheres with a diameter of 1-2.5 micron were prepared by a simple two-step calcination method. The initial oxygen reduction potential of the hollow microspheres was - 0.29 V during ORR. The initial oxygen evolution potential of the hollow microspheres was 50 mV lower than that of the irregular CoFe2O4 microspheres in OER, and the current density reached 45 mA cm-2 at 1 V. The ORR current density of CoFe2O4 hollow microspheres decreased by 16.4% and 5.6% after the same working time at - 0.3 V. (4) CoFe2O4/C composite catalyst with three-dimensional network structure was prepared by hydrothermal method using bacterial cellulose as template and carbon source. The initial potential of oxygen reduction of CoFe2O4/C was - 0.09 V and the limiting current density was 5.41 mA cm-2. In the process of OER catalysis, the initial voltage of oxygen evolution was 0.58 V, and the current density was 23.02 mA cm-2 at 1 V. When the CoFe2O4/C composite catalyst was continuously operated at - 0.3 V for 35000 seconds, the ORR current density decreased by 3.7% and 0.8 V. After the same working time, the current density of OER decreases by 5.8%. (5) LixNiCo2-xO4 doped with Li + was prepared by hydrothermal method. The ORR starting potential of Li0.5NiCo1.5O4 was - 0.176 V, the yield of intermediate product was less than 1%, and the electron transfer number was between 3.97-4. Mn2 + doped Mn_xNi1 was also prepared by hydrothermal method. The ORR initiation potential of Mn0.2Ni0.8Co2O4 is -0.13 V when x=0.2. The yield of intermediate product is less than 1.5% and the electron transfer number is between 3.96-4.
【学位授予单位】：苏州大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TM911.41;O643.36
本文编号：2214647
[Abstract]:Nowadays, the world is experiencing the reform of new energy system. Its main content is to replace fossil-based energy system with new renewable energy, to realize the transition from unsustainable modern industrial civilization to sustainable ecological civilization in the future, and finally to realize the organic integration of human society and the law of the Earth's biosphere cycle. Lithium-air batteries with high theoretical energy density have attracted extensive attention in all new energy storage devices developed. However, the slow kinetics of cathode oxygen reduction reaction (ORR) in the operation of lithium-air batteries will cause overpotential loss, resulting in a large difference between the actual and theoretical energy density and short cycle life. Nowadays, noble metals have good catalytic activity, especially Pt-type catalysts. However, due to the scarcity of precious metal resources and high price, it is difficult to use them in electrochemical catalysis. Therefore, the research and development of non-noble metal catalysts with high catalytic activity is the key to promote the commercialization of lithium-air batteries. In this paper, spinel oxides with good chemical stability, low price and high catalytic activity were selected as the research object, and yeast cells and bacterial cellulose were used as templates and carbon sources to prepare lithium-air batteries. C oFe2O4 and carbon composite catalysts with high catalytic activity and catalytic stability were doped with Li+ and Mn2+ as impurity ions respectively to improve the catalytic activity of NiCo2O4. The main contents and results were as follows: (1) Mesoporous C was prepared by chemical precipitation method using yeast cells as carbon source. OFe2O4/Co/C composite catalysts. Composite products with different electrochemical catalytic properties were prepared by adjusting the concentration of yeast suspension. When the concentration of yeast suspension was 10 g L-1, the specific surface area of the composite product CFO/Co/BC-2 could reach 92.76 M 2 g-1. It had good catalytic activity and catalytic stability under alkaline conditions. In the catalytic process, the initial potential of CFO/Co/BC-2 is - 0.176 V and the limiting current density is 7.25 mA cm-2. In the process of oxygen evolution reaction (OER), the initial potential of oxygen evolution is 0.58 V, and the current density is 26.48 mA cm-2 when the voltage is 1 V. (2) C oFe2O4/C composite microspheres with a diameter of 1-2.5 microrn were prepared by chemical precipitation and freeze-drying using yeast cells as carbon source and template. The C in the composite was the amorphous carbon doped with N and P produced by carbonization of yeast cells. CoFe2O4/C composite microspheres have good catalytic activity and stability under alkaline conditions. In ORR process, the initial potential of oxygen reduction of CoFe2O4/C composite microspheres is only - 0.14 V. In OER catalytic process, the initial potential of oxygen reduction of CoFe2O4/C composite microspheres is only - 0.14 V. The ORR current density of CoFe2O4/C composite microspheres decreased by 15.1% after 43 000 s continuous operation at - 0.35 V, and decreased by 1.4% after the same working time at 0.8 V. CoFe2O4 hollow microspheres with a diameter of 1-2.5 micron were prepared by a simple two-step calcination method. The initial oxygen reduction potential of the hollow microspheres was - 0.29 V during ORR. The initial oxygen evolution potential of the hollow microspheres was 50 mV lower than that of the irregular CoFe2O4 microspheres in OER, and the current density reached 45 mA cm-2 at 1 V. The ORR current density of CoFe2O4 hollow microspheres decreased by 16.4% and 5.6% after the same working time at - 0.3 V. (4) CoFe2O4/C composite catalyst with three-dimensional network structure was prepared by hydrothermal method using bacterial cellulose as template and carbon source. The initial potential of oxygen reduction of CoFe2O4/C was - 0.09 V and the limiting current density was 5.41 mA cm-2. In the process of OER catalysis, the initial voltage of oxygen evolution was 0.58 V, and the current density was 23.02 mA cm-2 at 1 V. When the CoFe2O4/C composite catalyst was continuously operated at - 0.3 V for 35000 seconds, the ORR current density decreased by 3.7% and 0.8 V. After the same working time, the current density of OER decreases by 5.8%. (5) LixNiCo2-xO4 doped with Li + was prepared by hydrothermal method. The ORR starting potential of Li0.5NiCo1.5O4 was - 0.176 V, the yield of intermediate product was less than 1%, and the electron transfer number was between 3.97-4. Mn2 + doped Mn_xNi1 was also prepared by hydrothermal method. The ORR initiation potential of Mn0.2Ni0.8Co2O4 is -0.13 V when x=0.2. The yield of intermediate product is less than 1.5% and the electron transfer number is between 3.96-4.
【学位授予单位】：苏州大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TM911.41;O643.36
【参考文献】
相关期刊论文 前1条
1 席国喜;邢新艳;范仁秀;路迈西;;废旧锂离子电池水热法制备钕掺杂钴铁氧体[J];电子元件与材料;2009年01期
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