单极脉冲法制备镍钴层状双金属氢氧化物及其电化学性能研究

发布时间：2018-05-31 02:30

本文选题：单极脉冲法 + 镍钴层状双金属氢氧化物　；参考：《太原理工大学》2017年硕士论文

【摘要】：能源危机和环境污染是目前全球亟待解决的两大问题,在此背景下,探索与发展新型清洁能源以及高效处理水体污染已成为科学研究的重要课题。层状双金属氢氧化物(Layered Double Hydroxides,简称LDHs,俗称类水滑石),是一种阴离子型的功能材料,具有纳米片层状形貌、并且其位于层间的阴离子可与其他阴离子进行交换。最近人们广泛研究LDH材料的结构和性能,探索其在催化、超级电容器、锂离子电池、水处理等方面的应用。LDH是一种主客体材料,主体是带正电荷的层板,是金属氢氧化物,客体是位于层间的阴离子和自由水分子。由于层状双金属氢氧化物独特的层状结构,使其具有较大的比表面积,用作超级电容器电极材料时,可以同时发挥双电层与赝电容两种性质的电容性能,从而获得相对较高的电容量;又由于层状双金属氢氧化物的层间阴离子具有可交换性,可以通过阴离子和功能性配体交换与其他离子形成配合物而应用在水处理领域。本文旨在用一种新型的电化学方法合成镍钴层状双金属氢氧化物(NiCo LDH)和其衍生的镍钴氧化物(NiCo CLDH)材料。本工作系统研究了NiCo LDH的超级电容器性能,此外由于NiCo LDH焙烧后具有“记忆效应”和更高的电活性,故将其用作电控离子交换(ESIX)膜材料,并且评价了其对磷酸根离子的回收性能。首先,使用单极脉冲电沉积法在碳纸基体上成功制备了NiCo LDH电极材料。考察了不同Ni~(2+)/Co~(2+)摩尔比的制膜液对合成材料的结构和性能的影响,发现合成NiCo LDH的形貌组成和性能与制膜液中Ni~(2+)/Co~(2+)摩尔比密切相关。当制膜液中Ni~(2+)/Co~(2+)摩尔比为9:1时,制得的电极材料(Ni_(0.76)Co_(0.24) LDH)形貌更均匀,纳米片尺寸更小,比表面积更大,具有较好的电容性能。通过对Ni_(0.76)Co_(0.24) LDH进行循环伏安测试、充放电测试、稳定性测试和交流阻抗测试得出:在1.0 A g~(-1)的电流密度下比电容高达2189.8 F g~(-1),且在50 A g~(-1)电流密度下进行20000次的恒电流充放电稳定性测试后比电容保持初始值的70.3%,其电荷转移电阻只有0.53Ω。以Ni_(0.76)Co_(0.24) LDH为正极,活性炭为负极组装成非对称型超级电容器,测试其电化学性能。测得非对称电容器的比电容可达到179.4 F g~(-1),在4.1 Wh Kg~(-1)的能量密度下,非对称电容器的功率密度高达4000 W Kg~(-1),并且在10 A g~(-1)电流密度下进行20000次充放电稳定性测试后,比电容仍保留初始值的82.7%。这表明Ni_(0.76)Co_(0.24) LDH电极具有良好的电容器性能,适合选作超级电容器电极材料。其次,合成的Ni_(0.76)Co_(0.24) LDH在管式炉中300℃下焙烧2 h,分别考察焙烧前后材料的电化学活性能,发现焙烧后膜电极材料的电活性提高。NiCo LDH和焙烧的NiCo LDH(即NiCo CLDH)被用作电控离子交换膜材料,分别测试其对PO_4~(3-)离子的吸附性能。实验表明,在0.8 V吸附电位下,NiCo LDH和NiCo CLDH膜电极分别对浓度为100 mg L~(-1)的PO_4~(3-)离子吸附6 h,NiCo CLDH膜电极对PO_4~(3-)离子吸附量达到225.7 mg g~(-1),而NiCo LDH的吸附量仅为166.6 mg g~(-1)。此后将NiCo CLDH膜材料在浓度均为100 mg L~(-1)的PO_4~(3-),SO_4~(2-)和Br~-的混合溶液中0.8 V吸附电位下同时吸附,测试膜材料的吸附选择性,测得对PO_4~(3-)的吸附量远远高于对SO_4~(2-)和Br~-的吸附量。另外本工作对吸附饱和的NiCo CLDH膜材料进行PO_4~(3-)离子脱附回收测试,结果表明在-0.4 V电位下脱附6 h后,由于NiCo CLDH的记忆效应,首次脱附率只有81.2%,但是在经过五次循环吸脱附后,吸附量仍高达160.2 mg g~(-1),而脱附率则上升为98.4%。此工作表明NiCo CLDH具有良好的PO_4~(3-)离子回收性能。
[Abstract]:The energy crisis and the environmental pollution are the two major problems to be solved in the world. In this context, the exploration and development of new clean energy and the efficient treatment of water pollution have become an important subject of scientific research. The layered double metal hydroxide (Layered Double Hydroxides, LDHs, commonly known as hydrotalcite) is an anionic power Energy materials, with nanoscale lamellar morphology, and their interlayer anions can exchange with other anions. Recently, the structure and properties of LDH materials have been extensively studied, and the application of.LDH in catalysis, supercapacitors, lithium ion batteries and water treatment is a kind of host material, and the main body is a positive charge laminar plate. Metal hydroxide, the object is an interlayer of anions and free water molecules. Due to the unique layered structure of layered double metal hydroxide, it has a larger specific surface area. When used as a supercapacitor electrode material, it can perform two kinds of capacitive properties at the same time, such as double layer and pseudopotential, so as to obtain relatively high capacitance. As the interlayer anion of layered double metal hydroxide is exchangeable, it can be used in the field of water treatment by exchanging anions and functional ligands with other ions to form complexes. The purpose of this paper is to synthesize nickel cobalt layered double gold hydroxide (NiCo LDH) and its derived nickel cobalt oxygen by a new electrochemical method. NiCo CLDH material. The performance of the supercapacitor of NiCo LDH is studied in this work system. In addition, because of "memory effect" and higher electrical activity after NiCo LDH roasting, it is used as an electronically controlled ion exchange (ESIX) membrane material, and the recovery performance of the phosphate ion is evaluated. First, the use of monopole electrodeposition is used in the system. The NiCo LDH electrode material was successfully prepared on the carbon paper matrix. The influence of the film solution of different Ni~ (2+) /Co~ (2+) molar ratio on the structure and properties of the synthetic material was investigated. It was found that the morphology and properties of the synthesized NiCo LDH were closely related to the Ni~ (2+) /Co~ (2+) molar ratio in the film liquid. The electrode material (Ni_ (0.76) Co_ (0.24) LDH) has more uniform morphology, smaller size, larger surface area and better capacitance. Through the cyclic voltammetric test of Ni_ (0.76) Co_ (0.24) LDH, charge discharge test, stability test and AC impedance test, it is found that the capacitance is up to 2189.8 F g~ (-1) under the current density of 1 A g~ (-1). After a 20000 constant current charge discharge stability test under 50 A g~ (-1) current density, the initial value of the charge discharge is 70.3%, the charge transfer resistance is only 0.53 Omega. Ni_ (0.76) Co_ (0.24) LDH is the positive pole, the active carbon is assembled into a negative electrode to form an asymmetric super electric container, and its electrochemical performance is tested. The ratio of the asymmetric capacitor is measured. The capacitance can reach 179.4 F g~ (-1). Under the energy density of 4.1 Wh Kg~ (-1), the power density of the asymmetrical capacitor is up to 4000 W Kg~ (-1), and after the 20000 charge discharge stability test under the 10 A g~ (-1) current density, the specific capacitance still keeps the initial value of 82.7%. This indicates that the electrode (0.76) (0.24) has a good capacitance. Ni_ (0.76) Co_ (0.24) LDH was baked for 2 h at 300 C in tube furnace, and the electrochemical activity of the materials before and after baking was investigated. It was found that the electrical activity of the film electrode material after roasting was improved by.NiCo LDH and the roasted NiCo LDH (NiCo CLDH) was used as an electronically controlled ion exchange membrane material. The adsorption properties of PO_4~ (3-) ions are not tested. The experiments show that the adsorption capacity of NiCo LDH and NiCo CLDH membrane electrodes is 6 for PO_4~ (3-) ions with a concentration of 100 mg L~ (-1) at 0.8 V adsorption potential. DH membrane materials are adsorbed at the same concentration of 100 mg L~ (-1) in PO_4~ (3-), SO_4~ (2-) and Br~- in a mixed solution of 0.8 V. The adsorption selectivity of the membrane material is measured. The adsorption capacity of PO_4~ (3-) is far higher than that of the adsorbent and the adsorption capacity of the adsorbent saturated membrane material. The desorption recovery test showed that after the desorption of 6 h at -0.4 V potential, the first desorption rate was only 81.2% due to the memory effect of NiCo CLDH, but after five cycles of desorption, the adsorption amount was still up to 160.2 mg g~ (-1), while the desorption rate increased to 98.4%., which showed that NiCo CLDH had a good recycling performance of PO_4~.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O611.64;TM53

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