硫酸化焙烧——水浸法从镍精矿中同步提取金属及矿相转化

提出低温NH_(4)HSO_(4)焙烧—水浸工艺从金川镍精矿中同步提取Ni、Cu和Co,并系统研究硫酸化焙烧和水浸出过程中一些因素对金属提取的影响。结果表明,在优化的焙烧和水浸条件下,95.7%Ni、98.9%Cu和96.8%Co被提取。利用TG-DTA、XRD、SEM和EDS等手段分析矿相的转化机理,在NH_(4)HSO_(4)及其分解的SO_(3)和NH3的硫酸化反应下,有价金属被转化为水溶性金属—铵配合物从而得到有效的提取。通过提高浸出温度使铁离子与铵离子结合形成NH_(4)[Fe_(3)(SO_(4))_(2)(OH)_(6)]沉淀可除去浸出液中的杂质铁。在焙烧过程中收集的挥发物为(NH_(4))_(2)SO_(4)和(NH_(4))_(2)SO_(3),可用作硫酸化焙烧的试剂。

CuO/CeO_(2) p−n异质结光催化降解亚甲基蓝的性能及机理

采用简单微波回流法和均相沉淀技术合成CuO/CeO_(2) p−n异质结复合材料,并对其光催化降解亚甲基蓝溶液的性能进行研究。CuO/CeO_(2)异质结复合材料的降解效率明显强于CeO_(2)。结果表明,以Cu/Ce摩尔比为1/3制备的复合材料(1/3 Cu/Ce)的光催化活性最高,在180 min内降解效率达到96.2%。CuO和CeO_(2)之间形成的p−n异质结促进了光生载流子的分离和传输,从而提高了其光催化活性。计算了CuO/CeO_(2)异质结的能带位置偏移,其价带偏移(∆EVBO)为1.58 eV,导带偏移(∆ECBO)为−0.48 eV。计算结果进一步证明CuO与CeO_(2)之间形成了p−n异质结。

优化水热合成提高ZnMn_(2)O_(4)阳极的储锂性能

为探讨制备条件对过渡金属氧化物负极材料电化学性能的影响,以硝酸锌和硝酸锰为原料,采用水热法合成了过渡金属氧化物ZnMn_(2)O_(4)负极材料。通过设计4因素3水平的正交试验,系统研究反应温度、反应时间、致密度、pH值等工艺参数对合成条件的影响。X射线衍射和扫描电镜证实ZnMn_(2)O_(4)具有微米级块状结构及I41/amd空间群。在优化的制备条件下,Li/ZnMn_(2)O_(4)电池的首次放电比容量为933.1 mA·h/g,在0.1C倍率下循环100次后放电比容量仍为249.3 mA·h/g。正交优化后的样品具有良好的循环性能和倍率性能。

Transformation and leaching kinetics of silicon from low-grade nickel laterite ore by pre-roasting and alkaline leaching process

The mineralogical phase transformation of a low-grade nickel laterite ore during pre-roasting process and the extraction of silicon during alkaline leaching process were investigated.The results indicate that the reaction activity of nickel ores is effectively improved by pre-roasting at650°C for2h,because of the transformation of lizardite into magnesium olivine and protoenstatite.When finely ground ore samples(44-61μm)pre-roasted firstly react with sodium hydroxide solution(60g/L)with a solid/liquid ratio of1:5at140°C for120min,the extraction of silicon can reach89.89%,and the other valuable elements of magnesium,iron and nickel are accumulated in the solid residues.The leaching kinetics of nickel laterite ore can be described successfully by the diffusion through the product layer control model.The activation energy is calculated to be11.63kJ/mol and the kinetics equation can be expressed as1-3(1-x)2/3+2(1-x)=13.53×10-2exp[-11.63/(RT)]t.

Raman spectroscopy and quantum chemical calculation on YCl_(3)-KCl molten salt system

The knowledge on the ionic structure of YCl_(3)-KCl molten system is of guiding significance for the practical production of yttrium metals and yttrium alloys via molten salt electrolysis using this system as electrolyte.In this paper,the theoretical Raman spectra of the ionic groups which may exist in YCl_(3)-KCl molten system are simulated by quantum chemical calculation using Gaussian09 and Gauss View 5.0 programs based on density functional theory(DFT).Then the ionic structures of 20 mol%-60 mol%YCl_(3)-KCl molten salt systems are studied by comparing the Raman shift values of the bands in the theoretical Raman spectra of different ionic groups with the experimental spectra of this system.YCl_(6)^(3-),Y_(2)Cl_(7)^(-),Y_(2)Cl_(8)^(2-)and Y_(2)Cl_(9)^(3-)are thought to exist in the molten system.With the increase of temperature,the relative content of YCl_(6)^(3-)ionic groups increases while those of Y_(2)Cl_(7)^(-),Y_(2)Cl_(8)^(2-)and Y_(2)Cl_(9)^(3-)ionic groups decrease.Moreover,the"lifetime"of all ionic groups decreases within the temperature range of 692-730℃.Meanwhile,the relative contents of Y_(2)Cl_(7)^(-),Y_(2)Cl_(8)^(2-)and Y_(2)Cl_(9)^(3-)increase with the increase of YCl_(3)content,while that of YCl_(6)^(3-)decreases.The wave function analysis of the four ionic groups(YCl_(6)^(3-),Y_(2)Cl_(7)^(-),Y_(2)Cl_(8)^(2-),and Y_(2)Cl_(9)^(3-))is carried out by Multiwfn program.The net charge in each group,the direction of electron migration during the formation of each group,the sites where electrophilic and nucleophilic reactions are most likely to occur in each ionic group,and the order of bond breaking during chemical reactions for the four groups are obtained.

In situ synthesis of Co_(3)O_(4)nanoparticles confined in 3D nitrogendoped porous carbon as an efficient bifunctional oxygen electrocatalyst

The rational exploitation of non-precious metal catalyst with high activity,strong durability and low cost for the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)is of vital importance for metalair batteries.Herein,a composite of Co_(3)O_(4)nanoparticles confined in three-dimensional(3 D)N-doped porous carbon(Co-NpCs)was prepared by a simple freeze-drying and in situ pyrolysis method.The effect of different dosages of Co(NO_(3))_(2)on the catalytic performance was discussed.The Co-NpC-12%exhibits the best catalytic performance(E_(1/2)=0.78 V,better stability than 20%Pt/C)in ORR and in OER among all the as-synthesized samples.Furthermore,it also exhibits the best bifunctional activity(ΔE=0.849 V).The excellent properties of Co-NpCs are mainly due to the synergy between Co_(3)O_(4)and carbon.Firstly,a high Co_(3)O_(4)loading amount can boost the defect level of the N-doped hierarchical porous carbon and expose more active sites.Secondly,the unique in situ pyrolysis guarantees a largearea contact between Co_(3)O_(4)and carbon as well as a strong C-O-Co bonding,which promotes charge transfer,avoids the peeling of Co_(3)O_(4)nanoparticles and effectively improves the stability of the material.This work is expected to offer a feasible strategy to produce metal oxide/carbon nanocomposite and push forward the development of bifunctional electrocatalyst with high activity and stability.

Sulfur-doped 3D hierarchical porous carbon network toward excellent potassium-ion storage performance

Carbonaceous materials are promising anode candidates for potassium-ion batteries, but currently the unsatisfactory cycling and rate performances due to the sluggish diffusion kinetic and serious structure damage during K+ insertion/extraction limit their practical application. Herein, a series of sulfur-doped porous carbons(SPCs) were prepared via a template-assisted freeze-drying followed by the carbonization and sulfuration processes at different temperatures. Among the three as-synthesized samples, SPC-600 exhibits the highest specific capacity(407 mAh·g^(-1) at 0.10 A·g^(-1)), the best rate(242 mAh·g^(-1) at 2.00 A·g^(-1)) and cycling performance(286 m Ah·g^(-1) after 800 cycles at 0.50 A·g^(-1)). All the SPCs display higher capacities than the undoped carbon materials. The excellent electrochemical performance of SPC can be ascribed to the abundant three-dimensional porous structure together with S-doping in the disordered carbon, which is favor of providing adequate reaction active sites as well as fast ion/electron transport paths. The density functional theory(DFT) calculations further demonstrate that the sulfurdoping can promote K-ion adsorption and storage. Meanwhile, the kinetic analyses reveal that surface-induced capacitive mechanism dominates the K-ion storage process in SPCs, which contributes to ultrafast charge storage. This work provides an effective strategy for fabricating highperformance potassium-ion storage electrode materials.

Biocarbon with different microstructures derived from corn husks and their potassium storage properties

In this paper,biocarbon was prepared from corn husks as anode materials for potassium ion batteries at temperatures ranging from 700 to 1600℃.The prepared biocarbon materials have amorphous phase structure and possess larger interlayer spacing than graphite.The biocarbon exhibits enhanced graphitic degree and decreased amounts of surface defects,while the carbonization temperature gradually increases.The obtained potassium ion battery electrode at 1300℃ acquired high reversible capacity up to 216.6 mAh·g^(-1) at 0.1 A·g^(-1) after 100 cycles, and retained 128.6 mAh·g^(-1) at 1 A·g^(-1) even after500 cycles.The results indicate that the samples prepared at 1300℃ have better electrochemical performance than other samples prepared at different temperatures,which was attributed to the decisive influence of microstructure on surface-induced and intercalating potassium storage.

High-entropy chemistry stabilizing spinel oxide(CoNiZnXMnLi)_(3)O_(4)(X=Fe,Cr)for high-performance anode of Li-ion batteries

High entropy oxides(HEOs),as a new type of single-phase multielement solid solution materials,have shown many attractive features and promising application prospect in the energy storage fleld.Herein,six-element HEOs(CoNiZnFeMnLi)_(3)O_(4) and(CoNiZnCrMnLi)_(3)O_(4) with spinel structure are successfully prepared by con-ventional solid-phase method and present outstanding lithium storage performances due to the synergy effect of various electrochemically active elements and the entropy stabilization.By contrast,(CoNiZnFeMnLi)_(3)O_(4) delivers higher initial discharge specific capacity of 1104.3 mAh·g^(−1),better cycle stability(84%capacity retention after 100 cycles at 100 mA·g^(−1)) and rate performance(293 mAh·g^(−1)at 2000 mA·g^(−1))in the half-cell.Moreover,the full-cell assembled with(CoNiZnFeMnLi)_(3)O_(4) and LiCoO_(2)provides a reversible specific capacity of 260.2 mAh·g^(−1)after 100 cycles at 500 mA·g^(−1).Ex situ X-ray diffraction reveals the electrochemical reaction mechanism of HEOs(CoNiZnFeMnLi)_(3)O_(4),and the amorphous phase and the large amount of oxygen vacancies were obtained after the initial discharge process,which are responsible for the excellent cycle and rate performance.This research puts forward fresh insights for the development of advanced energy storage materials for high-performance batteries.

Walnut septum-derived hierarchical porous carbon for ultra-high-performance supercapacitors

The conversion of biomass waste into eco-nomical and high-performance energy storage devices receives significant attention.Herein,a facile and green method to prepare porous active carbon from walnut sep-tum is applied to the electrode materials of supercapacitors.The effect of chemical etching reagent(KOH)on the microstructure and specific capacitance of the porous car-bon are explored.The modified BC-2.0,with a KOH/walnut septum mass ratio of 2∶1,exhibits large specific surface area of 1003.9 m^(2)·g^(-1)with hierarchical micro-mesoporous structures.BC-2.0 reveals a superior specific capacitance of 457 F·g^(-1)at 1 A·g^(-1).The flexible sym-metric supercapacitor in gel electrolyte(KOH/PVA)exhi-bits considerable synergetic energy-power output performance.The results indicate that walnut septum is a better precursor to obtain activated carbons relative to other biomass carbon sources.The large mesoporosity after activation effectively boosts the electrochemical properties of supercapacitor.Consequently,the walnut septum has potential to be a superior electrode material for supercapacitors.

Synthesis and electrochemical properties of Li FePO_(4) cathode material by ionic thermal method using eutectic mixture of tetramethyl ammonium chloride-urea

In this study, the LiFePO_(4) cathode was synthesized by the ionic thermal method using the deep eutectic mixture of tetramethyl ammonium chloride and urea. The synthetic conditions were systematically investigated by orthogonal experiments, which indicate that the optimal reaction time, reaction temperature, molar ratio of Li to DES and rotate speed are 96 h, 220 ℃, 1:14 and20 r·min^(-1), respectively. X-ray diffraction(XRD), scanning electron microscope(SEM) and transmission electron microscope(TEM) were characterized to investigate the crystalline structure and morphology of the obtained materials, indicating well-crystallized LiFePO_(4) with olivine structure. And the physical properties of LiFePO_(4) were explored through Fourier transform infrared spectroscopy(FTIR),57 Fe Mo¨ ssbauer absorption spectra and Raman spectra. An initial discharge capacity can reach 151 m Ah·g^(-1) at 0.1 C rate for LiFePO_(4) following by calcining at 600 ℃ under the optimal conditions, and it retains 125.1 m Ah·g^(-1) after 100 cycles. These results demonstrated that the addition of ionic liquids can improve the rate performance, cycle performance and ion diffusion rate of LiFePO_(4).

Synthesis and performance of Li_4Ti_5O_(12) anode materials using the PVP-assisted combustion method

Li4Ti5O12 was synthesized by a facile gel-combustion method（GCM） with polyvinylpyrrolidone（PVP） as the polymer chelating agent and fuel.The structural and electrochemical properties of the sample were compared with the one prepared by the conventional solid-state reaction（SSR） through X-ray diffraction（XRD）,scanning electron microscopy（SEM）,cyclic voltammetry（CV）,charge-discharge measurements,and electrochemical impedance spectroscopy（EIS）,respectively.The sub-microscale Li4Ti5O12 oxides,with a high phase purity and good stoichiometry,can be obtained by annealing at 800℃.The grain size is smaller than that of the samples that were power prepared by SSR.Lithium-ion batteries with a GCM Li4Ti5O12 anode exhibit excellent reversible capacities of 167.6,160.7,152.9,and 144.2 mAh/g,at the current densities of 0.5 C,1 C,3 C and 5 C,respectively.The excellent cycling and rate performance can be attributed to the smaller particle size,lower charge-transfer resistance and larger lithium ion diffusion coefficient.It is therefore concluded that GCM Li4Ti5O12 is a promising candidate for applications in highrate lithium ion batteries.