MOF-template derived hollow CeO_2/Co_3O_4 polyhedrons with efficient cathode catalytic capability in Li-O_2 batteries

Li-O_2 batteries(LOBs) have been perceived as the most potential clean energy system for fast-growing electric vehicles by reason of their environmentally friendlier,high energy density and high reversibility.However,there are still some issues limiting the practical application of LOBs,such as the large gap between the actual capacity level and the theoretical capacity,low rate performance as well as short cycle life.Herein,hollow CeO_2/Co_3 O_4 polyhedrons have been synthesized by MOF template with a simple method.And it is was further served as a cathode catalyst in Li-O_2 batteries.By means of the synergistic effect of two different transition metal oxides,nano-sized hollow porous CeO_2/Co_3 O_4 cathode obtained better capacity and cycle performance.As a result,excellent cyclability of exceeding 140 and 90 cycles are achieved at a fixed capacity of 600 and 1000 mAh/g,respectively.The successful application of this catalyst in LOBs offers a novel route in the aspect of the synthesis of other hollow porous composite oxides as catalysts for cathodes in LOBs systems by the MOF template method.     

Trithiocyanuric acid derived g-C_3N_4 for anchoring the polysulfide in Li-S batteries application

Lithium-sulfur (Li-S) batteries have great potential as an electrochemical energy storage system because of the high theoretical energy density and acceptable cost of financial and environment.However,the shuttle effect leads to severe capacity fading and low coulombic efficiency.Here,graphitic carbon nitride(g-C_3N_4) is designed and prepared via a feasible and simple method from trithiocyanuric acid (TTCA) to anchor the polysulfides and suppress the shuttle effect.The obtained g-C_3N_4 exhibits strong chemical interaction with polysulfides due to its high N-doping of 56.87 at%,which is beneficial to improve the cycling stability of Li-S batteries.Moreover,the novel porous framework and high specific surface area of g-C_3N_4 also provide fast ion transport and broad reaction interface of sulfur cathode,facilitating high capacity output and superior rate performance of Li-S batteries.As a result,Li-S batteries assembled with g-C_3N_4 can achieve high discharge capacity of 1200 mAh/g at 0.2 C and over 800 mAh/g is remained after 100 cycles with a coulombic efficiency more than 99.5%.When the C-rate rises to 5 C,the reversible capacity of Li-S batteries can still maintain at 607mAh/g.     

CeO_2@NiCo_2O_4 nanowire arrays on carbon textiles as high performance cathode for Li-O_2 batteries

The successful development of Li-O_2 battery technology depends on developing a stable and efficient cathode. As an important step toward this goal, for the first time, we report the development of CeO_2 nanoparticles modified NiCo_2O_4 nanowire arrays(NWAs) grown on the carbon textiles as a new carbon-free and binder-free cathode system. In this study, the Li-O_2 battery with the CeO_2@NiCo_2O_4 NWAs has exhibited much reduced overpotentials, a high discharge capacity, an improved cycling stability,outperforming the Li-O_2 battery with NiCo_2O_4 NWAs. These improvements can be attributed to both the tailored morphology of discharge product and improved oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) activity after CeO_2 NPs deposition. To a considerable extent, this idea of cathode construction including structure design and composition optimization can provide guidance for further researches in developing more powerful cathode for Li-O_2 battery.     

Reinforced polysulfide barrier by g-C_3N_4/CNT composite towards superior lithium-sulfur batteries

The notorious shuttle effect has long been obstructing lithium-sulfur(Li-S) batteries from yielding the expected high energy density and long lifespan.Herein,we develop a multifunctional polysulfide barrier reinforced by the graphitic carbon nitride/carbon nanotube(g-C_3 N_4/CNT) composite toward inhibited shuttling behavior and improved battery performance.The obtained g-C_3 N_4 delivers a unique spongelike architecture with massive ion transfer pathways and fully exposed active interfaces,while the abundant C-N heteroatomic structures impose strong chemical immobilization toward lithium polysulfides.Combined with the highly conductive agent,the g-C_3 N_4/CNT reinforced separator is endowed with great capability of confining and reutilizing the active sulfur within the cathode,thus contributing to an efficient and stable sulfur electrochemistry.Benefiting from these synergistic attributes,Li-S cells based on g-C_3 N_4/CNT separator exhibit an excellent cyclability with a minimum decay rate of 0.03% per cycle over 500 cycles and decent rate capability up to 2 C.Moreover,a high areal capacity of 7.69 mAh cm^-2can be achieved under a raised sulfur loading up to 10.1 mg cm^-2.demonstrating a facile and efficient pathway toward superior Li-S batteries.     

锂离子电池正极材料LiNi_(0.85)Co_(0.10)(TiMg)_(0.025)O_2合成及表征

以LiOH·H2O、Ni2O3、Co2O3、TiO2和Mg(OH)2为原料,应用固相反应法合成Co Ti Mg共掺杂的LiNiO2化合物LiNi0. 85Co0. 10 (TiMg)0. 025O2;TG DTA、XRD、SEM和电化学测试表明,该材料首次放电容量达182. 7mAh/g(3. 0~4. 3V, 18mA/g), 10次循环之后,容量还有 175. 5mAh/g,容量保持率为 96. 2%;与未掺杂的LiNiO2相比,该材料显示出良好的循环性能,是一种很有应用前景的锂电池正极材料.     

一维纳米Co_3O_4,Ag/Co_3O_4及CuO/Co_3O_4的合成与电催化性能(英文)

采用水热合成法制备了Co3O4及复合Ag/Co3O4、CuO/Co3O4一维纳米产品。用XRD,FE-SEM和TEM手段对产品进行了表征。采用循环伏安法研究了合成产品修饰的玻碳电极在碱性溶液中对对硝基苯酚的电催化还原性能。与裸玻碳电极相比,1mmol·L-1的对硝基苯酚在用Co3O4、特别是CuO/Co3O4修饰的玻碳电极上还原的峰电流明显增大,用Ag/Co3O4(Ag/Co原子比分别为1∶5和2∶5)修饰的玻碳电极催化还原对硝基苯酚时,尽管还原峰电流增大不是太大,但其峰电位明显降低(分别降低0.265和0.371V)。     

g-C_3N_4/Ag/GO Composite Photocatalyst with Efficient Photocatalytic Performance: Synthesis,Characterization, Kinetic Studies,Toxicity Assessment and Degradation Mechanism

The g-C_3N_4/Ag/GO(CNAG) photocatalysts were synthesized by a facile two-step reaction route. The as-prepared CNAG samples were characterized by X-ray diffraction(XRD), Fourier transform-infrared spectroscopy(FTIR), X-ray photoelectron spectroscopy(XPS), photoluminescence spectroscopy(PL) and ultraviolet-visible diffuse reflectance spectroscopy techniques(UV-vis DRS). The photocatalytic activity was obtained by degrading rhodamine B(RhB) under simulated sunlight and the results showed that photocatalytic activity of CNAG was much higher than that of pure g-C_3N_4 and g-C_3N_4/Ag. When the mass ratio of GO was 6%, the as-prepared CNAG-6% sample possessed the highest photocatalytic activity and the kinetic constant of RhB degradation was 0.077 min~(-1), which was almost 4.3 times higher than that of pure g-C_3N_4(0.018 min~(-1)) and 2.5 times higher than that of the g-C_3N_4/Ag(0.031 min~(-1)) composite, respectively. The toxicity of CNAG samples was assessed via seed germination experiment and no significant inhibitory effect was observed. The enhanced photocatalytic activity could be attributed to the synergistic effect of partial surface plasma resonance(SPR) effect of Ag, strong visible light absorption and the high separation efficiency of photon-generated carrier. The CNAG-6% sample exhibited excellent stability during the cycle experiment. Finally, a possible photocatalytic mechanism was proposed.     

The design and fabrication of Co_3O_4/Co_3V_2O_8/Ni nanocomposites as high-performance anodes for Li-ion batteries

The Co_3O_4/Co_3V_2O_8/Ni nanocomposites were rationally designed and prepared by a two-step hydrothermal synthesis and subsequent annealing treatment. The one-dimensional(1D) Co_3O_4 nanowire arrays directly grew on Ni foam, whereas the 1D Co_3V_2O_8 nanowires adhered to parts of Co_3O_4 nanowires.Most of the hybrid nanowires were inlayed with each other, forming a 3D hybrid nanowires network.As a result, the discharge capacity of Co_3O_4/Co_3V_2O_8/Ni nanocomposites could reach 1201.8 mAh/g after100 cycles at 100 mA/g. After 600 cycles at 1 A/g, the discharge capacity was maintained at 828.1 mAh/g.Moreover, even though the charge/discharge rates were increased to 10 A/g, it rendered reversible capacity of 491.2 mAh/g. The superior electrochemical properties of nanocomposites were probably ascribed to their unique 3D architecture and the synergistic effects of two active materials. Therefore, such Co_3O_4/Co_3V_2O_8/Ni nanocomposites could potentially be used as anode materials for high-performance Li-ion batteries.     

LiNi0.8Co0.2-XMXO2的合成和电化学性能研究

锂离子电池手机、笔记本电脑、电动汽车技术、医疗仪器电源以及宇宙空间等领域。目前商品化锂离子电池正极活性材料主要是LiCoO2、LiNiO2、LiMn2O4，及其掺杂化合物。LiNiO2具有比容量高，功率大、价格适中等优点，但也存在合成困难，热稳定性差等问题，其实用化进程一直比较缓慢。     

电导研究贵金属Pt在Co3O4还原过程中的作用

通过考察Co3O4在还原过程中电导率的变化, 并结合程序升温还原方法, 对贵金属Pt的作用进行了研究. 另外, 研究了Co3O4在氢气、氧气和合成气气氛中电导率的连续变化过程, 以便进一步了解Co3O4在实际费-托合成反应条件下的氧化-还原历程, 以及贵金属Pt在该过程中的作用.     

Effect of cobalt oxide on performance of Pd catalysts for lean-burn natural gas vehicles in the presence and absence of water vapor

Pd-based catalysts modified by cobalt were prepared by co-impregnation and sequential impregnation methods, and characterized by X-ray powder diffraction (XRD), N_2 adsorption/desorption (Brunauer-Emmet-Teller method), CO-chemisorption and X-ray photoelectron spec-troscopy (XPS). The activity of Pd catalysts was tested in the simulated exhaust gas from lean-burn natural gas vehicles. The effect of Co on the performance of water poisoning resistance for Pd catalysts was estimated in the simulated exhaust gas with and without the presence of water vapor. It was found that the effect of Co significantly depended on the preparation process. PdCo/La-Al_2O_3 catalyst prepared by co-impregnation exhibited better water-resistant performance. The results of XPS indicated that both CoAl_2O_4 and Co_3O_4 were present in the Pd catalysts modified by Co. For the catalyst prepared by sequential impregnation method, the ratio of CoAl_2O_4/Co_3O_4 was higher than that of the catalyst prepared by co-impregnation method. It could be concluded that Co_3O_4 played an important role in improving water-resistant performance.     

The Co_3O_4 nanosheet array as support for MoS_2 as highly efficient electrocatalysts for hydrogen evolution reaction

The electrochemical hydrogen evolution reaction(HER) on a non-precious electrocatalyst in an alkaline environment is of essential importance for future renewable energy. The design of advanced electrocatalysts for HER is the most important part to reduce the cost and to enhance the efficiency of water splitting. MoS_2 is considered as one of the most promising electrocatalysts to replace the precious Pt catalyst.Herein, for the first time, we have successfully loaded MoS_2 electrocatalysts onto the Co_3O_4 nanosheet array to catalyze HER with a low onset potential of ~76 mV. The high hydrogen evolution activity of MoS_2 supported on the Co_3O_4 nanosheet array may be attributed to the increased active sites and the electronic interactions between MoS_2 and Co_3O_4.     

Assembling Co_9S_8 nanoflakes on Co_3O_4 nanowires as advanced core/shell electrocatalysts for oxygen evolution reaction

Rational design of advanced cost-effective electrocatalysts is vital for the development of water electrolysis. Herein, we report a novel binder-free efficient Co_9S_8@Co_3O_4 core/shell electrocatalysts for oxygen evolution reaction(OER) via a combined hydrothermal-sulfurization method. The sulfurized net-like Co_9S_8 nanoflakes are strongly anchored on the Co_3O_4 nanowire core forming self-supported binder-free core/shell electrocatalysts. Positive advantages including larger active surface area of Co_9S_8 nanoflakes,and reinforced structural stability are achieved in the Co_9S_8@Co_3O_4 core/shell arrays. The OER performances of the Co_9S_8@Co_3O_4 core/shell arrays are thoroughly tested and enhanced electrocatalytic performance with lower over-potential(260 m V at 20 m A cm~(-2)) and smaller Tafel slopes(56 mV dec-1) as well as long-term durability are demonstrated in alkaline medium. Our proposed core/shell smart design may provide a new way to construct other advanced binder-free electrocatalysts for applications in electrochemical catalysis.     

Porous nanostructured ZnCo_2O_4 derived from MOF-74:High-performance anode materials for lithium ion batteries

Nanostructured metal oxides derived from metal organic frameworks have been shown to be promising materials for application in high energy density lithium ion batteries. In this work, porous nanostructured ZnCo_2O_4 and Co_3O_4 were synthesized by a facile and cost-effective approach via the calcination of MOF-74 precursors and tested as anode materials for lithium ion batteries. Compared with Co_3O_4, the electrochemical properties of the obtained porous nanostructured ZnCo_2O_4 exhibit higher specific capacity, more excellent cycling stability and better rate capability. It demonstrates a reversible capacity of 1243.2 m Ah/g after 80 cycles at 100 m A/g and an excellent rate performance with high average discharge specific capacities of 1586.8, 994.6, 759.6 and 509.2 m Ah/g at 200, 400, 600 and 800 m A/g, respectively.The satisfactory electrochemical performances suggest that this porous nanostructured ZnCo_2O_4 is potentially promising for application as an efficient anode material for lithium ion batteries.     

Cr2O3-Co3O4／SiO2对十八醇氧化生成十八酸反应的催化性能

 制备了一系列不同Cr／Co比例的Cr2O3－Co3O4／SiO2催化剂，并用XRD，FT－IR和BET等手段对催化剂进行了表征；考察了催化剂对十八醇氧化生成十八酸反应的催化性能，及反应条件（反应温度和反应时间）对催化性能的影响，确定了最佳反应条件．结果表明，金属硝酸盐在773K焙烧后转变成相应的氧化物并负载于二氧化硅上．Cr2O3－Co3O4／SiO2催化剂对十八醇氧化反应有很高的催化活性，十八酸选择性最高可达99．93％，收率可达52．44％．Cr2O3－Co3O4／SiO2催化剂的活性明显高于单一的Cr2O3／SiO2或Co3O4／SiO2催化剂     

Nanostructured Ni/Ti_3C_2T_x MXene hybrid as cathode for lithium-oxygen battery

Ti_3C_2 belongs to MXenes family,which is a new two-dimensional material and has been applied in many fields.With simple method of hydrothermal and high temperature calcination,nano structured Ni/Ti_3C_2T_x hybrid was synthesized.The stable layer structure of Ti_3C_2 MXene providing high surface area as well as excellent electronic conductivity are beneficial for deposition and decomposition of discharge product Li_2O_2.Furthermore,possessing special catalytic activity,Ni nanoparticles with size of about 20 nm could accelerate Li_2O_2 breaking down.Taking advantage of two kinds of materials,Ni/Ti_3C_2T_x hybrid as cathode of Li-O_2 battery can achieve a maximal specific capacity of 20,264 mAh/g in 100 mA/g and 10,699 mAh/g in 500 mA/g at the first cycle.This work confirms that the prepared Ni/Ti_3C_2T_x hybrid exhibiting better cycling stability points out a new guideline to improve the electrochemical performance of lithium-oxygen batteries.     

以α型氢氧化物前驱体制备LiNi_(0.8)Co_(0.15)Al_(0.05)O_2及其电化学性能

本文采用球形Al/Co部分取代α型Ni(OH)2为前驱体成功制备了锂离子电池正极材料LiNi0.8Co0.15Al0.05O2。首先采用氢氧化钠与碳酸钠为沉淀剂合成出Al/Co部分取代α型Ni(OH)2,然后将之与LiOH·H2O混合,最后在氧气气氛中不同温度下热处理8h,即可得到球形LiNi0.8Co0.15Al0.05O2材料。X射线衍射结果表明,LiNi0.8Co0.15Al0.05O2材料为α-NaFeO2相。扫描电镜结果表明,材料颗粒形貌为球形。热重分析结果表明合成LiNi0.8Co0.15Al0.05O2的主反应温度在700～750℃之间。振实密度测试结果表明,750℃下制备的LiNi0.8Co0.15Al0.05O2材料可达2.2g·cm-3。恒流充放电结果表明,该材料在0.5mA·cm-2电流密度下,在3.0～4.3V间的首次充电容量可达210.3mAh·g-1,首次放电容量为179.7mAh·g-1,充放电效率为85.4%。与采用以β-Ni0.85Co0.15(OH)2为前驱体合成的LiNi0.85Co0.15O2和Al掺杂的LiNi0.8Co0.15Al0.05O2相比,尽管其首次放电容量与放电效率都有所降低,但循环性能有所提高,50周期后容量仍为初始容量的89.5%。研究表明,以球形Al/Co部分取代α型Ni(OH)2作为前驱体为球形氧化镍钴铝锂材料的制备提供了一条新的途径。     

碱性溶液中Ag_3O_4的电化学性质及反应机理

首次研究高价银氧化物Ag3O4(可看作为由Ag(Ⅲ)和Ag(Ⅱ)*组成)在碱性水溶液中的电化学性质和反应机理.循环伏安和XRD测试表明,Ag3O4在碱性溶液中的电化学还原过程比较复杂:在较慢的放电条件下,Ag3O4中的Ag(Ⅲ)按照Ag(Ⅲ)→Ag(Ⅱ)→Ag(Ⅰ)→Ag反应途径逐步还原为单质银;在较快的放电条件下,Ag(Ⅲ)可以直接被还原为Ag(Ⅰ),即Ag(Ⅲ)→Ag(Ⅰ)→Ag.而Ag(Ⅱ)*可直接还原成金属Ag.Ag3O4的理论放电容量可以达到553.1 mAh/g,比通常锌-氧化银电池所用AgO的电容量高出27.8%.在119C放电倍率下,Ag3O4的放电容量依然达到理论容量的83%.显示了作为新型化学电源材料的应用前景.     

Al2O3负载Ag催化剂的杀菌作用

 考察了空气中Al2O3负载的Ag催化剂(Ag/Al2O3和AgCl/Al2O3)对大肠杆菌(E.coli)的杀灭作用. 结果表明,负载Ag的催化剂的杀菌效果明显好于Al2O3. 在空气中,催化剂上溶出的Ag+对细菌的重金属毒性可以忽略. Ag/Al2O3, AgCl/Al2O3和Al2O3在有氧和无氧条件下的杀菌效果表明, Ag促进了催化剂表面分子态氧向活性氧转化,活性氧通过氧化作用破坏E.coli 的细胞膜,从而提高了催化剂的杀菌能力. 扫描电镜结果证实在催化剂表面E.coli细胞的破坏是从细胞膜开始的.     

钛基氧化物电极的性能及电化学行为

本文研究了某些氧化物中间层对Ti/PbO_2、Ti/MnO_2、Ti/Co_3O_4和Ti/CuCo_2O_4电极性能及电化学行为的影响。结果表明,Ti/MnO_2或Ti/PbO_2电极在加入Co_3O_4、PdO_x、SnO_2或Sb_2O_3中间层后,界面电阻大大降低。在低于出现电阻极化电流密度时,极化曲线符合Tafel规律(无论对于O_2或Cl_2,低极化区的Tafel斜率为厶b_1=2.303RT/(1+β)F;高极化区为b_2=2,303RT/βF,其中β=0.5)这时主要为电化学极化。对有中间层Sb_2O_3+PdO_x的Ti/PbO_2电极和具有中间层SnO_2+PdO_x的Ti/Co_3O_4电极,其阳极析Cl_2的反应活性与工业用的Ti/RuO_2+TiO_2电极相近,而氧的过电位则高于Ti/RuO_2+TiO_2电极。