廉价模板法制备MnO2纳米棒及其电容特性研究

该文以可再生、廉价、天然多孔的锯末为模板,采用化学溶液浸渍法合成了MnO2纳米棒.TEM,FTIR,XRD测试结果表明,所得样品为α-MnO2纳米棒,其平均直径为15 nm左右,平均长度约为150 nm.循环伏安和恒流充放电测试结果表明:在1.0 mol?L-1的(NH4)2SO4电解液中,0～1.0 V(vs.SCE)电位区间内,充放电的电流密度分别为1 A?g-1和2 A?g-1时,所制备的α-MnO2的最高放电比电容分别达到了176 F?g-1和138 F?g-1.     

低温熔盐法制备MnO2及其电容性能研究

采用低温熔盐法在150 ℃的KCl-AlCl3体系中制备了MnO2,并对其结构和形貌进行表征,XRD结果表明所制样品主相为α-MnO2,SEM结果表明样品为微米级片状结构.以所制备的MnO2作为电极活性物质,在2 mol/L的(NH4)2SO4电解液中对其电化学性质进行测试和研究.循环伏安结果表明该材料具有良好的电容性能,用恒流充放电测得在1 mA条件下,放电比电容可达290.72 F·g-1.经5 mA恒电流循环100次后电极性能趋于稳定,充放电效率接近100%,表现出优异的循环性能.     

无机盐水溶液反应合成MnO2纳米粉体及其电容特性

采用无机盐水溶液反应合成了纳米MnO2粉末。X射线衍射结果表明：所制备的MnO2是a-MnO2与γ-MnO2的混合晶相。透射电镜分析表明：所制备的MnO2粒径为4～20nm。由所制备的粉末在300℃煅烧3h后作为活性物质制成电极。在1mol／L的(NH4)2SO4电解液中,在电位范围(以饱和甘汞电极为参比电极)为0．15～0．75V的三电极体系中,通过循环伏安曲线考察了电极的电容性能。循环伏安结果表明：所制备的纳米MnO2具有优异的电容性能,通过恒流充放电测得其比容量最高可达150．4F／g,循环2～3次后．充放电曲线进入稳定状态,说明纳米MnO2具有较好的循环充放电性能。作为电极材料,纳米MnO2具有较好的应用前景。     

纳米锰氧化物超级电容器电极材料的制备与性能

采用模板和液相沉淀两种方法制备了锰的氧化物,XRD的测试结果表明,两种方法制备的锰氧化物分别为MnO2和Mn3O4。从TEM图可以看出,模板法制备的MnO2为直径为5~8nm左右的颗粒,而用液相沉淀制备的Mn3O4形貌为直径约为10nm左右的纤维棒。循环伏安和充放电测试结果都表明MnO2是更好的超电容器的电极材料。MnO2和Mn3O4在200mA·g-1电流密度下的放电比电容分别为157.5和145.0F·g-1,经过500次充放电后比电容分别为132.5和125.0F·g-1,充放电效率分别为64.9%和63.7%。     

熔盐法合成MnO2粉体及其超级电容性能

采用熔盐法在不同温度下制备了MnO2粉体.X射线衍射仪分析表明:粉体样品为α-MnO2和γ-MnO2晶混合物,反应温度越高样品的结晶程度越好.将MnO2粉体与石墨、乙炔黑、聚四氟乙烯、羧甲基纤维素按质量比为75:10:10:2:3进行混合,在10 MPa压力下压制成电极.在2 mol/L (NH4)2SO4溶液中,用三电极体系对MnO2电极样品进行电化学性能测试.结果表明:制备粉体的反应温度是影响MnO2粉体制备的电极的电化学性能的重要因素,反应温度为450 ℃的粉体制备的电极样品电容性能最好.循环伏安测试表明该样品在0～1.0 V电位窗口范围内具有较好的矩形特征;交流阻抗测试结果显示样品具有典型的电容阻抗特性,其等效串联电阻和电极反应电阻分别为0.064 Ω和2.825 Ω.在电流密度为2 mA/cm2,恒流充放电时测得其放电比容量可达246.46 F/g.     

α-MnO_2纳米针的电容性能

通过简单的水热法合成了α-MnO2纳米针,将其用作超级电容器电极材料,通过循环伏安和恒电流充放电测试手段对α-MnO2纳米针电极进行分析。结果表明,以1mol·L-1 Na2SO4为电解液,电极在-0.6~0.6V的电压范围内具有良好的法拉第电容特性;在电流密度为0.01A·g-1时,电极的比电容最高达56.7F·g-1,且500次循环后,比电容保持率为82%,表明其具有良好的循环性能。     

不同质量比PANI∕α-MnO2超级电容器材料的制备及表征

在酸性条件下采用液相共沉淀法合成球状和海胆状的α-MnO2,并以α-MnO2为氧化剂,H2SO4溶液为介质,引发苯胺聚合制备得到不同质量比的聚苯胺(PANI)/α-MnO2复合物。采用XRD、FTIR、SEM等法对材料的形貌和物相进行表征,同时采用循环伏安、计时电位法考察了PANI/α-MnO2复合物在1 mol/L Na2SO4水系电解液中的电化学性能。结果表明,起始原料m(苯胺)∶m(α-MnO2)=1∶3制备的PANI/α-MnO2复合物,在制备电极过程中其质量未到α-MnO2质量一半的条件下,PANI/α-MnO2复合物的比电容达到64.58 F/g,是所合成的α-MnO2比电容(43.49 F/g)的1.48倍,且经过600次循环,其比电容保持率在85%以上,而α-MnO2只有57%的比电容保持率。     

不同质量比PANI/α-MnO_2超级电容器材料的制备及表征

在酸性条件下采用液相共沉淀法合成球状和海胆状的α-MnO2,并以α-MnO2为氧化剂,H2SO4溶液为介质,引发苯胺聚合制备得到不同质量比的聚苯胺(PANI)/α-MnO2复合物。采用XRD、FTIR、SEM等法对材料的形貌和物相进行表征,同时采用循环伏安、计时电位法考察了PANI/α-MnO2复合物在1 mol/L Na2SO4水系电解液中的电化学性能。结果表明,起始原料m(苯胺)∶m(α-MnO2)=1∶3制备的PANI/α-MnO2复合物,在制备电极过程中其质量未到α-MnO2质量一半的条件下,PANI/α-MnO2复合物的比电容达到64.58 F/g,是所合成的α-MnO2比电容(43.49 F/g)的1.48倍,且经过600次循环,其比电容保持率在85%以上,而α-MnO2只有57%的比电容保持率。     

掺杂型纳米MnO2/Al2O3催化剂的制备及催化臭氧化处理驱油污水二级出水

以Al2O3为载体,制备了掺杂型纳米MnO2/Al2O3催化剂,考查了最佳制备条件;研究了臭氧催化氧化法处理驱油废水二级生化处理出水的效果及其影响因素.结果表明,制备的纳米MnO2催化剂的XRD谱图中可以明显看到α-MnO2的衍射峰;动态光散射仪(DLS)分析表明纳米MnO2的粒度主要分布在80～180 nm之间,从XRD、扫描电镜(SEM)和透射电镜(TEM)表征可知.α-MnO2主要呈球形,其直径在25～50 nm之间;催化剂的比表面积达到157.48 m2·g-1.催化剂的最佳焙烧温度和焙烧时间分别为550℃和4h;活性组分含量为6％时,MnO2/A12 O3催化剂的催化活性最强.当进水COD为100～ 120 mg·L-1、MnO2/Al2 O3催化剂的投量为70 mg·L-、臭氧投量为240 mg·h-1,催化臭氧氧化30 min时,有机物的去除率达到55％以上,出水COD指标满足《污水综合排放标准》一级A标准.·OH氧化在臭氧催化氧化降解有机污染物体系中起主导作用,其平均产生速率为30.84 μmmol·L-1·min-1.制备的掺杂型纳米MnO2/Al2O3催化剂具有制备方法简单、催化效率高、使用寿命长、二次污染小等优点.     

熔盐法制备λ-MnO_2及其超级电容性能

在600℃的m(NaC l)∶m(L iC l)=1∶3的熔盐体系中,将KMnO4反应5 h制备了MnO2。X射线衍射分析其结构表明,所制样品为λ-MnO2;扫描电镜对其形貌研究表明,样品为微米级片状结构。按m(MnO2)∶m(石墨)∶m(乙炔黑)∶m(羧甲基纤维素)∶m(聚四氟乙烯)=75∶10∶10∶3∶2制备电极材料,在电解液为c〔(NH4)2SO4〕=2mol/L的三电极体系中,通过循环伏安、交流阻抗和恒流充放电对其超级电容性能进行了考察。不同扫速循环伏安曲线表明,该材料具有典型的超级电容特性;交流阻抗测试结果表明,溶液电阻RL为0.69Ω,电极电阻RE为2.5Ω;用恒流充放电测得在1 mA恒流充放电条件下,放电比容量可达306.92 F.g-1。经5 mA恒电流循环100次,充放电效率接近100%。     

基于β-FeOOH纳米棒制备LiFePO_4/C和Fe_2O_3纳米电极材料及其电池性能

自制直径为90nm、长为500nm的β-FeOOH纳米棒为前驱物,通过碳热还原法和热分解法分别制备出形貌均匀、粒径为300nm的LiFePO4/C正极材料和粒径为100nm的Fe2O3负极材料,并研究它们对金属锂组成半电池和构造LiFePO4/C vs.Fe2O3全电池的电化学性能。结果表明：LiFePO4/C半电池在0.1C、0.5C、1.0C、5.0C、10.0C和15.0C（1C=170 mA g–1）倍率下放电比容量分别为158.8、153.2、144.3、126.8、111.0 mA h g–1和92.9mA h g–1。经过不同倍率循环后,返回0.1 C放电比容量为157.5mA h g–1,为初始0.1 C放电比容量的99.2%。Fe2O3半电池在50mA g–1电流密度下首次放电比容量为1655.5mA h g–1,循环50次后,仍保持460mA h g–1的放电比容量。LiFePO4/C vs.Fe2O3全电池在0.1 C倍率下,相对于LiFePO4活性物质,首次放电比容量为148.7mA h g–1;相对于Fe2O3活性物质,首次放电比容量为441.7mA h g–1。由LiFePO4/C纳米粒子作为正极材料、Fe2O3纳米粒子作为负极材料组成的全电池在0.1 C到2.0 C不同倍率下均表现出了良好的循环性能,且返回0.1 C后其放电比容量相对于初始0.1 C放电比容量无衰减。可见,以β-FeOOH纳米棒为前驱物控制制备的LiFePO4/C正极纳米材料和Fe2O3负极纳米材料可以有效地提升电池的性能。     

Synthesis of zinc oxide nanostructures on graphene/glass substrate by electrochemical deposition: effects of current density and temperature

The electrochemical growth of zinc oxide (ZnO) nanostructures on graphene on glass using zinc nitrate hexahydrate was studied. The effects of current densities and temperatures on the morphological, structural, and optical properties of the ZnO structures were studied. Vertically aligned nanorods were obtained at a low temperature of 75°C, and the diameters increased with current density. Growth temperature seems to have a strong effect in generating well-defined hexagonal-shape nanorods with a smooth top edge surface. A film-like structure was observed for high current densities above -1.0 mA/cm² and temperatures above 80°C due to the coalescence between the neighboring nanorods with large diameter. The nanorods grown at a temperature of 75°C with a low current density of -0.1 mA/cm² exhibited the highest density of 1.45 × 10⁹ cm^-2. X-ray diffraction measurements revealed that the grown ZnO crystallites were highly oriented along the c-axis. The intensity ratio of the ultraviolet (UV) region emission to the visible region emission, I_UV/I_VIS, showed a decrement with the current densities for all grown samples. The samples grown at the current density below -0.5 mA/cm² showed high I_UV/I_VIS values closer to or higher than 1.0, suggesting their fewer structural defects. For all the ZnO/graphene structures, the high transmittance up to 65% was obtained at the light wavelength of 550 nm. Structural and optical properties of the grown ZnO structures seem to be effectively controlled by the current density rather than the growth temperature. ZnO nanorod/graphene hybrid structure on glass is expected to be a promising structure for solar cell which is a conceivable candidate to address the global need for an inexpensive alternative energy source.     

稀土Nd~(3+)与Cu~(2+)掺杂非晶态纳米Ni(OH)_2材料的电化学性能

晶态氢氧化镍[Ni(OH)2]在碱性电解液中易发生相变,影响其电化学性能。文中采用微乳液快速冷冻共沉淀法制备Nd3+和Cu2+复合掺杂非晶态纳米Ni(OH)2粉体材料,并对其结构形貌及物理特性进行表征分析。结果表明,制备出的非晶态Ni(OH)2样品材料,微结构含有较多结晶水,物相近似球形,粒径大小在20—30nm。对样品电极材料的电化学性能测试发现,掺杂Nd3+和Cu2+的摩尔比为2∶1时,所制备的样品材料合成镍电极,并组装成MH-Ni模拟电池,在恒电流80mA/g下充电6h,40mA/g放电,终止电压为1.0V的充放电条件下,放电比容量高达348.0mA.h/g,放电中值电压为1.2723V,同时样品电极材料的氧化还原可逆性较好,电极过程的电化学阻抗较小。电化学性能优于目前MH-Ni生产应用的晶态β-Ni(OH)2电极材料。     

二氧化钼纳米棒的制备及电化学性能研究

MoO2纳米棒具有高电导率、高熔点及比容量较大,在超级电容器电极材料领域应用前景广泛。现有MoO2纳米棒制备方法大多存在操作复杂、收率低、成本高、易引入杂质等问题,且这些方法制备的MoO2产品存在形貌不均一、分散性差、电化学性能低的问题。基于此,本工作以双氧水和钼粉制备的过氧钼酸前驱体为钼源,PEG (8000)为模板剂制备出带状结构含钼杂化物,然后以浆态带状杂化物为原料采用两段式全湿法工艺制备纳米棒状MoO2。利用X射线衍射(XRD)、X射线光电子能谱(XPS)、X射线能谱(EDS)和扫描电子显微镜(SEM)等对二氧化钼纳米棒的物相、表面组成与形貌进行了分析,同时分别采用三电极和两电极体系研究了MoO2纳米棒的电化学电容行为,考察了MoO2纳米棒直接作为电极组装电容的性能。结果表明,所制的MoO2为长约500~800 nm、宽约100~200 nm的棒状结构,形貌与尺寸均匀,具有良好的分散性和较高的纯度。以MoO2纳米棒制备的电极在1 A/g的电流密度下,三电极和两电极体系所测得比电容分别为366.7和290.4 F/g;在5 A/g电流密度下循环充放电2000次后电容保持率均高于72%,展现出了良好的电化学性能。该研究结果可为纳米金属氧化物的制备提供新方法。     

β-MnO_2纳米棒的循环伏安行为研究

β MnO2纳米棒的水热合成过程中,w(CH3COOH)=3%水溶液的加入对其晶型、形貌、结晶程度没有影响。样品B0102的水热合成时间是B0508的0 6倍,其结晶程度也是B0508的0 6倍。样品B0102中存在的晶格缺陷使其在浓度为9mol/L的KOH水溶液中还原/氧化时,可以发生晶型的转化,从而使第2次循环伏安曲线形状明显不同于第1次。结晶程度较高的样品B0508,其1×1隧道结构在还原过程中易发生结构崩溃,使其循环伏安曲线中还原/氧化峰电流迅速下降。     

n-ZnO nanorods/p-CuSCN heterojunction light-emitting diodes fabricated by electrochemical method

n-ZnO nanorods/p-CuSCN heterojunction light-emitting diodes (LEDs) have been fabricated using low-temperature electrochemical method. The I-V characteristics of the heterojunction LEDs show obvious rectifying behavior. The typical room-temperature electroluminescence spectra obtained from this heterostructure device under forward bias exhibit a strong visible emission across the spectral region from 350 to 600 nm centered at 530 nm. The intensity of the visible emission rises more quickly than that of the ultraviolet emission with the increasing bias. Photocurrent and Raman spectra reveal that the growth process of CuSCN can induce more surface states and defects in the ZnO nanorods, which confirms the enhancement of visible emission from the ZnO nanorods/p-CuSCN heterostructure. Compared with the ZnO-only LEDs, a p-type CuSCN layer used as a hole-transporting material can balance the electrons and holes injection rates in the heterojunction LEDs. The processing procedure in this work is a low-cost, low-temperature and convenient way to fabricate ZnO-based heterojunction light-emitting diodes.     

Surfactant-free electrochemical synthesis of fluoridated hydroxyapatite nanorods for biomedical applications

Fluoridated hydroxyapatite (FHA) [Ca₁₀(PO₄)₆F_x(OH)_2−x, x = 0–2] is believed to be a promising calcium phosphate (CaP) to replace pure hydroxyapatite (HA) for next-generation implants, owing to its better biocompatibility, higher antibacterial activity, and lower solubility. Notably, the shape and size of the CaP crystals play key roles in their performance and can influence their applications. One-dimensional (1D) FHA nanorods are important CaP materials which have been widely used in regenerative medicine applications such as restorative dentistry. Unfortunately, the traditional synthesis methods for FHA nanorods either employ surfactants or take a relatively long time. In this study, we aimed to propose a facile synthesis route to fabricate FHA nanorods without any surfactants using an electrochemical deposition method for the first time. This study focused on preparing FHA nanorods without the assistance of any surfactant, unlike the traditional synthesis methods, to avoid chemical impurities. FHA nanorods with lengths of 124–2606 nm, diameters of 28–211 nm, and aspect ratios of 4.4–21.8 were synthesized using the electrochemical method, followed by a heat treatment. For the as-synthesized FHA nanorods, the Ca/P ratio was 1.60 and the atomic concentration of F was 2.06 at.%. An ultrastructure examination revealed that each FHA nanorod possessed long-range order, good crystallinity, and a defect-free lattice with a certain crystallographic plane orientation along the whole rod. In short, we propose a novel, surfactant-free, cost-saving, and more efficient route to synthesize FHA nanorods which can be widely applied in multiple biomedical applications, including drug delivery, bone repair, and restorative dentistry.     

γ-MnOOH纳米棒的低温水热制备及其电化学性能

采用低温水热法,在弱碱性介质中氧化MnSO4制备了γ-MnOOH.应用X-射线衍射和扫描电镜技术对所得材料的结构和形貌进行表征.γ-MnOOH直径在100~150 nm之间,长度约为2 μm.电化学测试结果表明,γ-MnOOH纳米棒负极材料具有高的比容量、优异的循环性能和倍率性能.在100 mA/g的电流密度下,首次放电比容量高达1454 mAh/g.恒流充放电100次后,比容量仍达到720 mAh/g.     

Highly conductive vertically aligned molybdenum nanowalls and their field emission property

ABSTRACT: We report that vertically aligned molybdenum (Mo) nanowalls can grow on various substrates by simple thermal vapor deposition. Individual nanowalls have a typical thickness of about 50 nm and very good conductivity with a typical average value of about 1.97 [MULTIPLICATION SIGN] 104 [OHM SIGN][MINUS SIGN]1 cm[MINUS SIGN]1, i.e., only an order of magnitude less than the value of bulk Mo. The formation process is characterized in detail, and it is found that Mo nanowalls grow from nanorods through nanotrees. The atomic arrangement, lattice mismatch relationship, and competition growth are all believed to contribute to the growth mechanism. The field emission performance is attractive, typically with a very low fluctuation of about approximately 1.18% at a high current density level of 10 mA/cm2, and a sustainably stable very large current density of approximately 57.5 mA/cm2 was recorded. These indicate that the Mo nanowall is a potential candidate as a cold cathode for application in vacuum electron devices, which demand both a high current and high current density.