一锅法制备Co3O4/g-C3N4复合光催化剂及其光催化性能

以三聚氰胺和六水合氯化钴为原料,一锅法制备Co_3O_4负载的多孔石墨相氮化碳(Co_3O_4/g-C_3N_4)复合光催化材料。采用X射线衍射(XRD)、傅里叶变换红外(FT-IR)光谱、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、紫外-可见漫反射光谱(UV-Vis DRS)、光致发光光谱(PL)等手段对其结构和光学特性进行表征。以盐酸四环素(TC)为目标污染物,评价了不同负载量Co_3O_4/g-C_3N_4复合光催化剂的可见光催化性能。结果表明,所制备的Co_3O_4/g-C_3N_4复合光催化剂为多孔结构,其比表面积较大,并在可见光区域具有显著的吸收。利用原位生成的Co_3O_4纳米粒子在氮化碳表面形成异质结构,可有效转移光生载流子,降低光生电子-空穴的再结合率,从而提高光催化活性。并且存在最佳Co_3O_4复合量,当六水合氯化钴加入量为三聚氰胺的8%(w/w)时,所制备的复合光催化剂CoCN-8具有最佳的光催化性能。在可见光的照射下,60 min内可降解85%的TC,而同样条件下,纯g-C_3N_4仅降解23%的TC。     

Facile synthesis of ultrafine Co3O4 nanocrystals embedded carbon matrices with specific skeletal structures as efficient non-enzymatic glucose sensors

A facile, effective, and environmentally friendly method has been adopted for the first time to prepare tiny Co₃O₄ nanocrystals embedded carbon matrices without using surfactants, harmful organic reagents or extreme conditions. Structural characterizations reveal that the size-controlled Co₃O₄ nanocrystals are uniformly dispersed on carbon matrices. Electrochemical measurements reveal that Co₃O₄-ordered mesoporous carbon (OMC) can more efficiently catalyze glucose oxidation and acquire better detection parameters compared with those for the Co₃O₄-macroporous carbon, Co₃O₄-reduced graphene oxide, and free Co₃O₄ nanoparticles (NPs) (such as: the large sensitivity (2597.5 μA cm⁻² mM⁻¹ between 0 and 0.8 mM and 955.9 μA cm⁻² mM⁻¹ between 0.9 and 7.0 mM), fast response time, wide linear range, good stability, and surpassingly selective capability to electroactive molecules or Cl⁻). Such excellent performances are attributed to the synergistic effect of the following three factors: (1) the high catalytic sites provided by the uniformly dispersed and size-controlled Co₃O₄ nanocrystals embedded on OMC; (2) the excellent reactant transport efficiency caused by the abundant mesoporous structures of OMC matrix: (3) the improved electron transport in high electron transfer rate (confinement of the Co₃O₄ NPs in nanoscale spaces ensured intimate contact between Co₃O₄ nanocrystals and the conducting OMC matrix). The superior catalytic activity and selectivity make Co₃O₄-OMC very promising for application in direct detection of glucose.     

A New Method for the Preparation of Co3O4 Nanoparticles

In this study, a novel method was used to prepare well-separated and spherical tricobalt tetraoxide (Co₃O₄) nanosized particles. The overall process involves three steps: preparation of insoluble carboxyl-containing grafted starch copolymer (ISC), formation of precursor (ISC-Co), decomposition of ISC-Co, and phase transition of Co₃O₄ nanoparticles. The Infrared spectra used for ISC and ISC-Co are discussed. The decomposition of the precursor was studied by thermogravimetric-differential thermal analysis, the crystalline phase was characterized by x-ray diffraction, and the size distribution and shape of particles were observed by transmission electron microscopy. Translated from Journal of Northwest Normal University (Natural Science Edition), 2005, 5(5) (in Chinese)     

Porous cobalt oxide (Co3O4) nanorods: Facile syntheses, optical property and application in lithium-ion batteries

We developed a facile synthetic route of porous cobalt oxide (Co₃O₄) nanorods via a microemulsion-based method in combination with subsequent calcination process. The porous structure was formed by controlled decomposition of the microemulsion-synthesized precursor CoC₂O₄ nanorods without destruction of the original morphology. The as-prepared Co₃O₄ nanorods, consisting of small nanoparticles with diameter of 80–150 nm, had an average diameter of 200 nm and a length of 3–5 μm. The morphology and structure of synthesized samples were characterized by transmission electron microscopy and scanning electron microscopy. The phase and composition were investigated by X-ray powder diffraction and X-ray photoelectron spectroscopy. The optical property of Co₃O₄ nanorods was investigated. Moreover, the porous Co₃O₄ nanorods exhibited high electrochemical performance when applied as cathode materials for lithium-ion batteries, which gives them good potential applications.     

Co3O4纳米立方体的可控合成及其CO氧化反应性能

在乙醇和三乙胺的混合溶液中,采用溶剂热法制备了尺寸为10 nm的Co₃O₄立方体. 考察了钴盐前驱体和溶解氧对Co₃O₄纳米立方体结构的影响规律,通过对合成过程中不同阶段产物的结构分析和表征,提出了Co₃O₄纳米立方体的形成机制是溶解再结晶的过程. 将所制备的Co₃O₄纳米立方体在200 ℃焙烧处理后,尺寸和形貌均可保持稳定,但400 ℃焙烧后,变为球形纳米粒子. 这种主要暴露{100}晶面的Co₃O₄纳米立方体催化CO氧化反应的活性低于纳米粒子({111}晶面),验证了四氧化三钴纳米材料在CO氧化反应中的晶面效应.     

A simple and effective strategy to synthesize Al2O3-coated LiNi0.8Co0.2O2 cathode materials for lithium ion battery

A facile method has been developed to synthesize Al₂O₃-coated LiNi_0.8Co_0.2O₂ cathode materials. The sample was characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and energy dispersive analysis of X-rays (EDAX). Electrochemical tests show that the cycling stability of LiNi_0.8Co_0.2O₂ at room temperature is effectively improved by Al₂O₃ coating. The differential scanning calorimetry (DSC) and high temperature (60 °C) cycling tests indicate that Al₂O₃ coating can also improve the thermal stability of LiNi_0.8Co_0.2O₂, which is attributed to that the coating layer can protect the LiNi_0.8Co_0.2O₂ particles from reacting with the electrolyte.     

Li4Mn5O12包覆对三元正极材料结构和性能的影响

LiNi(1/3)Mn(1/3)Co(1/3)O2具有很高的理论比容量,但是三元正极材料在高电压下长循环时,其表面结构发生较大的衰退,导致电池的循环性能和倍率性能变差。本文采用耐高电压且结构稳定的富锂尖晶石Li4Mn5O(12)包覆LiNi(1/3)Mn(1/3)Co(1/3)O2可以有效改善材料的电化学性能。通过XRD、SEM、XPS和TEM等手段对包覆后的材料进行分析,证实了在LiNi(1/3)Mn(1/3)Co(1/3)O2的表面形成了10nm厚的均匀Li4Mn5O(12)的包覆层;在循环100圈后,包覆后的LiNi(1/3)Mn(1/3)Co(1/3)O2仍具有179.5m Ah/g的放电比容量和88.6%容量保持率,明显高于未包覆的LiNi(1/3)Mn(1/3)Co(1/3)O2的78.3%容量保持率。因此,利用富锂尖晶石Li4Mn5O(12)包覆LiNi(1/3)Mn(1/3)Co(1/3)O2为实现更高能量密度的锂离子电池提供了新的途径。     

Structure and magnetic properties of the orthorhombic n=2 Ruddlesden-Popper phases Sr3Co2O5+δ (δ=0.91, 0.64 and 0.38)

The reduced Ruddlesden-Popper phases, Sr₃Co₂O_5+δ with δ=0.91, 0.64 and 0.38, have been prepared in a nitrogen atmosphere. The crystal structures were determined by powder neutron diffraction. Oxygen vacancies are found both in O(3) and O(4) sites but the majority are along one crystallographic axis in the CoO₂ plane, inducing an orthorhombic distortion of the normally tetragonal n=2 Ruddelsden-Popper structure. Superstructures due to oxygen ordering are observed by electron microscopy. The magnetic measurements reveal complex behavior with some ferromagnetic interactions present for Sr₃Co₂O_5.91 and Sr₃Co₂O_5.64.     

Hydrothermal synthesis of cobalt carbonates using different counter ions: An efficient precursor to nano-sized cobalt oxide (Co3O4)

Synthesis of submicrometer crystalline particles of cobalt carbonate was achieved hydrothermally using different cobalt salts and urea with a molar ratio from 1:3 to 1:20 (cobalt salt:urea) in aqueous solutions at 160 °C for 24-36 h, in the presence of cetyltrimethylammonium bromide (CTAB) as a surfactant. Nanoparticles of Co₃O₄, with an average size from 30 to 39 nm, were obtained by thermal decomposition of CoCO₃ samples at 500 °C for 3 h in an electrical furnace. The as-synthesized products were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-Vis spectra and thermal analysis. Studying the optical properties of the as-prepared cobalt oxide nanoparticles showed the presence of two band gaps, the values of which confirmed the semiconducting properties of the prepared Co₃O₄.     

氮掺杂碳纳米管负载Co3O4氧还原电催化剂的制备与性能

以碳纳米管(CNT)为原料,通过负载维生素B₁₂,简单热解得到了一种氮掺杂碳纳米管(N/CNT)负载低含量Co₃O₄纳米颗粒的氧还原电催化剂(Co₃O₄@N/CNT)。得益于均匀分散的Co₃O₄纳米颗粒以及氮掺杂,Co₃O₄@N/CNT表现出了优异的氧还原催化性能,其半波电位达到了0.844 V(vs RHE),超越了商业Pt/C(0.820 V(vs RHE))。与Pt/C相比,基于Co₃O₄@N/CNT组装的锌-空气电池表现出了更优的放电性能和循环稳定性。     

氮掺杂碳纳米管负载Co3O4氧还原电催化剂的制备与性能

以碳纳米管(CNT)为原料,通过负载维生素B₁₂,简单热解得到了一种氮掺杂碳纳米管(N/CNT)负载低含量Co₃O₄纳米颗粒的氧还原电催化剂(Co₃O₄@N/CNT)。得益于均匀分散的Co₃O₄纳米颗粒以及氮掺杂,Co₃O₄@N/CNT表现出了优异的氧还原催化性能,其半波电位达到了0.844 V(vs RHE),超越了商业Pt/C(0.820 V(vs RHE))。与Pt/C相比,基于Co₃O₄@N/CNT组装的锌-空气电池表现出了更优的放电性能和循环稳定性。     

NixCo3-xO4表面修饰对CdSe/TiO2纳米管阵列光电化学氧化水活性的影响

利用氨挥发诱导法在CdSe/TiO2纳米管阵列表面负载一层NixCo3-xO4。采用SEM、XRD、XPS、UV-Vis对样品进行表征,通过线性扫描伏安法测定光阳极的释氧电势来评价其光电水氧化活性。结果表明:表面NixCo3-xO4是尖晶石结构;相对于CdSe/TiO2纳米管阵列光阳极,NixCo3-xO4/CdSe/TiO2光阳极能将光电氧化水的过电势降低430 mV。Ni离子的引入使得NixCo3-xO4表面富含三价阳离子(Ni3+,Co3+),从而促进CdSe/TiO2光阳极光电水氧化的进行。     

氨蒸发诱导法制备纳米结构LiNi1/3Co1/3Mn1/3O2及其作为高功率型锂离子电池正极材料的性能

采用氨蒸发诱导法成功制备出纳米结构LiNi_1/3Co_1/3Mn_1/3O₂正极材料,借助X射线衍射（XRD）分析、扫描电镜（SEM）、透射电镜（TEM）、高分辨率透射电镜（HRTEM）、能量分散谱（EDS）和比表面测试等表征手段及恒电流充放电测试研究了其晶体结构、微观形貌和电化学性能. 研究表明该方法制备出的材料具有良好的α-NaFeO₂层状结构,阳离子混排程度低. 纳米片交错堆积而成核桃仁状形貌,片与片之间形成许多纳米孔,而且纳米片的侧面属于{010}活性面,能够提供较多的锂离子的脱嵌通道. 在室温下及3.0-4.6 V充放电范围内,该材料在电流密度为0.5C、1C、3C、5C和10C时放电比容量分别为172.90、153.95、147.09、142.16 和131.23mAh·g^-1. 说明其具有优异的电化学性能,非常有潜力用于动力汽车等高功率密度锂离子电池中.     

The disordered cubic structure of Ca7Co3Ga5O18

The new mixed oxide having composition close to Ca₇Co₃Ga₅O₁₈ was synthesized from CaCO₃, Co₃O₄ and Ga₂O₃ at 1150 °C in air and studied by neutron and synchrotron X-ray powder diffraction, selected-area electron diffraction and high-resolution electron microscopy. The structure was refined, using time-of-flight (TOF) neutron powder diffraction data, in space group F432, with and Z=8, to R_F=0.7%. It is considerably disordered, with four different tetrahedral sites randomly occupied by Co and Ga atoms at a ratio of 1:2. The tetrahedra form a disordered (Co_1/3Ga_2/3)O₂ 3D-framework inside which isolated CoO₆ octahedra, surrounded by 8 Ca atoms, are located. The structure is related to the ordered structure of Ca₁₄Al₁₀Zn₆O₃₅. Electron diffraction patterns confirmed the symmetry and unit cell and revealed no diffuse scattering. High-resolution electron microscopy images showed the absence of extended structural defects.     

多层多孔Co3O4纳米粒子组装体的合成、表征和电化学性能研究

利用十二烷基磺酸钠(SDS)作为表面活性剂,合成了形貌化的CoC₂O₄配合物前驱物,然后在500 ℃下热分解形貌化的前驱物,得到了多层多孔Co₃O₄纳米粒子组装体。采用FESEM、TEM、HRTEM、XRD、N₂吸附脱附和Raman散射等手段对产物进行了分析和表征。低角XRD,TEM和N₂吸附脱附测试表明所得组装体具有多孔结构。常规XRD、HRTEM和Raman结果证明组装体中Co₃O₄纳米粒子建筑块结晶较好。与体相Co₃O₄晶体相比,Co₃O₄纳米粒子组装体的5个拉曼活性峰发生了明显的红移。将Co₃O₄纳米粒子组装体作为锂离子电池的正极材料进行了电化学性能测试,结果表明该组装体电极的首次放电容量为1 115 mAh·g^-1,远高于目前文献报道的Co₃O₄纳米管、纳米粒子和纳米棒电极。但是,该组装体电极的循环性能不好,有待进一步提高。     

Synthesis of Silica@α-Fe2O3 nanospheres by surface-initiated ATRP

We reported a new method to prepare Silica@α-Fe₂O₃ nanospheres by surface-initiated atom transfer radical polymerization (ATRP). Firstly, polymerizable surfactants-modified α-Fe₂O₃ nanoparticles were prepared in water-toluene microemulsion. Then, as-synthesized α-Fe₂O₃ nanoparticles acted as the macro-monomer of surface-initiated ATRP on silica nanospheres to make target product. Morphological characterization of the product was performed using transmission electron microscopy (TEM). Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance UV-vis spectroscopy were used to verify the incorporation of α-Fe₂O₃ nanoparticles on silica nanosphere.     

高效析氧电催化剂Co3O4@NiMn-LDH异质结构阵列的制备

我们合理设计和制备了一种新型的高性能析氧电催化剂——泡沫镍负载Co_3O_4@NiMn-LDH(层状双金属氢氧化物)三维异质结构阵列(Co_3O_4@NiMn-LDH/NF)。这种基于泡沫镍基底的三维异质结构催化剂经简单的两步水热反应即可制得。对比Co_3O_4、NiMn-LDH及传统RuO2催化剂,所制备的Co_3O_4@NiMn-LDH/NF催化剂展示出更优异的电催化析氧性能。在1 mol·L~(-1)KOH溶液中,电流密度为50 mA·cm~(-2)时的过电势仅为282 mV,塔菲尔斜率为64 mV·dec~(-1)。通过有效的界面工程设计,使异质结构陈列Co_3O_4@NiMn-LDH发挥出Co_3O_4和NiMn-LDH各自优异的电催化性能。其中,基于泡沫镍基底生长的活性组分Co_3O_4纳米线阵列作为中间核支撑结构,保持了良好的空隙率,不仅有利于暴露更多的活性位点,而且有利于电解液的扩散和气体产物的释放;而依附于Co_3O_4纳米线阵列上的NiMn-LDH异质结构纳米片层则富有更多的亲水性基团,使得活性位点更易与水结合,从而促进氧析出反应的进行。     

Enzyme mimics of spinel-type CoxNi1−xFe2O4 magnetic nanomaterial for eletroctrocatalytic oxidation of hydrogen peroxide

A series of spinel-type Co_xNi_1−xFe₂O₄ (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0) magnetic nanomaterials were solvothermally synthesized as enzyme mimics for the eletroctrocatalytic oxidation of H₂O₂. X-ray diffraction and scanning electron microscope were employed to characterize the composition, structure and morphology of the material. The electrochemical properties of spinel-type Co_xNi_1−xFe₂O₄ with different (Co/Ni) molar ratio toward H₂O₂ oxidation were investigated, and the results demonstrated that Co_0.5Ni_0.5Fe₂O₄ modified carbon paste electrode (Co_0.5Ni_0.5Fe₂O₄/CPE) possessed the best electrocatalytic activity for H₂O₂ oxidation. Under optimum conditions, the calibration curve for H₂O₂ determination on Co_0.5Ni_0.5Fe₂O₄/CPE was linear in a wide range of 1.0 × 10⁻⁸–1.0 × 10⁻³ M with low detection limit of 3.0 × 10⁻⁹ M (S/N = 3). The proposed Co_0.5Ni_0.5Fe₂O₄/CPE was also applied to the determination of H₂O₂ in commercial toothpastes with satisfactory results, indicating that Co_xNi_1−xFe₂O₄ is a promising hydrogen peroxidase mimics for the detection of H₂O₂.     

富锂掺杂Li1.06Co0.05Cr0.1Mn1.85O4的合成及电化学性能研究

锂离子电池具有比能量高、功率大、使用寿命长、无记忆效应、性能价格比高等优点,从而成为可充式电源的主要选择对象.锰由于资源丰富、价廉、环境友好等优点,使锰酸锂(LiMn2O4)成为最有希望取代钴酸锂的正极材料.但锰酸锂的放电容量相对较低,结构欠稳定,容量衰减严重,作为正极材料还无法与钴酸锂相比,近年来做了大量的研究工作以改善它的电化学性能[1～6].最近Youngjoon Shin等研究发现[7]用少量的Li与Ni共同替代LiMn2O4中的Mn得到的LiMn2-2yLiyNiyO4的电化学性能要优于单元素替代的LiMn2-xMxO4(M=Li,Cr,Fe,Co,Ni)的电化学性能.