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.     

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.     

Free-standing ternary metallic sulphides/Ni/C-nanofiber anodes for high-performance lithium-ion capacitors

As a promising energy-storage device,the hybrid lithium-ion capacitor coupling with both a large energy density battery-type anode and a high power density capacitor-type cathode is attracting great attention.For the sake of improving the energy density of hybrid lithium-ion capacitor,the free-standing anodes with good electrochemical performance are essential.Herein,we design an effective electrospinning strategy to prepare free-standing MnS/Co_4S_3/Ni_3S_2/Ni/C-nanofibers(TMSs/Ni/C-NFs)film and firstly use it as a binder-free anode for hybrid lithium-ion capacitor.We find that the carbon nanofibers can availably prevent MnS/Co_4S_3/Ni_3S_2/Ni nanoparticles from aggregation as well as significantly improve the electrochemical performance.Therefore,the binder-free TMSs/Ni/C-NFs membrane displays an ultrahigh reversible capacity of 1246.9 m Ah g~(-1)at 100 m A g~(-1),excellent rate capability(398 mAh g~(-1) at2000 mA g~(-1)),and long-term cyclic endurance.Besides,we further assemble the hybrid lithium-ion capacitor,which exhibits a high energy density of 182.0 Wh kg~(-1)at 121.1 W kg~(-1)(19.0 Wh kg~(-1) at 3512.5 W kg~(-1))and remarkable cycle life.     

Metallic Co4N Porous Nanowire Arrays Activated by Surface Oxidation as Electrocatalysts for the Oxygen Evolution Reaction

Designing highly efficient electrocatalysts for oxygen evolution reaction (OER) plays a key role in the development of various renewable energy storage and conversion devices. In this work, we developed metallic Co₄N porous nanowire arrays directly grown on flexible substrates as highly active OER electrocatalysts for the first time. Benefiting from the collaborative advantages of metallic character, 1D porous nanowire arrays, and unique 3D electrode configuration, surface oxidation activated Co₄N porous nanowire arrays/carbon cloth achieved an extremely small overpotential of 257 mV at a current density of 10 mA cm⁻², and a low Tafel slope of 44 mV dec⁻¹ in an alkaline medium, which is the best OER performance among reported Co‐based electrocatalysts to date. Moreover, in‐depth mechanistic investigations demonstrate the active phases are the metallic Co₄N core inside with a thin cobalt oxides/hydroxides shell during the OER process. Our finding introduces a new concept to explore the design of high‐efficiency OER electrocatalysts.     

Co_3O_4 modified Ag/g-C_3N_4 composite as a bifunctional cathode for lithium-oxygen battery

Rechargeable lithium-oxygen(Li-O_2)batteries have appeal to enormous attention because they demonstrate higher energy density than the state-of-the-art Li-ion batteries.Whereas,their practical application is impeded by several challenging problems,such as the low energy round trip efficiencies and the insufficient cycle life,due to the cathode passivation caused by the accumulation of discharge products.Developing efficient catalyst for oxygen reduction and evolution reactions is effective to reduce the overpotentials in Li-O_2cells.In our work,we report a Co_3O_4modified Ag/g-C_3N_4nanocomposite as a bifunctional cathode catalyst for Li-O_2cells.The g-C_3N_4substrate prevents the accumulation of Ag and Co_3O_4nanoparticles and the presence of Ag NPs improves the surface area of g-C_3N_4and electronic conductivity,significantly improving the oxygen reduction/evolution capabilities of Co_3O_4.Due to a synergetic effect,the Ag/g-C_3N_4/Co_3O_4nanocomposite demonstrates a higher catalytic activity than each individual constituent of Co_3O_4or Ag/g-C_3N_4for the ORR/OER on as catalysts in Li-O_2cells.As a result,the Ag/gC_3N_4/Co_3O_4composite shows impressive electrochemical performance in a Li-O_2battery,including high discharge capacity,small gap between charge and discharge potential,and high cycling stability.     

TiC/C core/shell nanowires arrays as advanced anode of sodium ion batteries

High-perfo rmance anodes of sodium ion batteries(SIBs)largely depends on rational architecture design and binder-free smart hybridization.Herein,we report TiC/C core/shell nanowires arrays prepared by a one-step chemical vapor deposition(CVD)method and apply it as the anode of SIBs for the first time.The conductive TiC core is intimately decorated with carbon shell.The as-obtained TiC/C nanowires are homogeneously grown on the substrate and show core/shell heterostructure and porous architecture with high electronic conductivity and reinforced stability.Owing to these merits,the TiC/C electrode displays good rate performance and outstanding cycling performance with a capacity of 135.3 mAh/g at 0.1 A/g and superior capacity retention of 90.14%after 1000 cycles at 2 A/g.The reported strategy would provide a promising way to construct binder-free arrays electrodes for sodium ion storage.     

Nickel-iron borate coated nickel-iron boride hybrid for highly stable and active oxygen evolution electrocatalysis

The development of efficient and cost-effective electrocatalysts toward anodic oxygen evolution reaction (OER) is crucial for the commercial application of electrochemical water splitting. As the most promising electrocatalysts, the OER performances of nickel-iron-based materials can be further improved by introducing metalloid elements to modify their electron structures. Herein, we developed an efficient hybrid electrocatalyst with nickel-iron boride (NiFeB) as core and amorphous nickel-iron borate (NiFeB_i) as shell (NiFeB@NiFeB_i) via a simple aqueous reduction. The obtained NiFeB@NiFeB_i exhibits a small overpotential of 237 mV at 10 mA/cm² and Tafel slope of 57.65 mV/dec in 1.0 mol/L KOH, outperforming most of the documented precious-metal-free based electrocatalysts. Benefiting from the in situ formed amorphous NiFeBi layer, it shows excellent stability toward the oxygen evolution reaction (OER). These findings might provide a new way to design advanced precious-metal-free electrocatalysts for OER and the application of electrochemical water splitting.     

Surpassing electrocatalytic limit of earth-abundant Fe~(4+) embedded in N-doped graphene for(photo)electrocatalytic water oxidation

Developing highly active,cost-effective,and environmental friendly oxygen evolution reaction(OER)electrocatalysts facilitates various(photo)electrochemical processes.In this work,Fe3N nanoparticles encapsulated into N-doped graphene nanoshells(Fe₃N@NG)as OER electrocatalysts in alkaline media were reported.Both the experimental and theoretical comparison between Fe₃ N@NG and Fe₃N/NG,specifically including in situ Mossbauer analyses,demonstrated that the NG nanoshells improved interfacial electron transfer process from Fe₃N to NG to form high-valence Fe⁴⁺ions(Fe⁴⁺@NG),thus modifying electronic properties of the outer NG shells and subsequently electron transfer from oxygen intermediate to NG nanoshells for OER catalytic process.Meanwhile,the NG nanoshells also protected Fe-based cores from forming OER inactive and insulated Fe₂O₃,leading to high OER stability.As a result,the as-formed Fe⁴⁺@NG shows one of the highest electrocatalytic efficiency among reported Fe-based OER electrocatalysts,which can as well highly improve the photoelectrochemical water oxidation when used as the cocatalysts for the Fe₂O₃ nanoarray photoanode.     

Boosting Electrocatalytic Oxygen Evolution over Ce−Co9S8 Core–Shell Nanoneedle Arrays by Electronic and Architectural Dual Engineering

An dual electronic and architectural engineering strategy is a good way to rationally design earth-abundant and highly efficient electrocatalysts of the oxygen evolution reaction (OER) for sustainable hydrogen-based energy devices. Here, a Ce-doped Co₉S₈ core–shell nanoneedle array (Ce−Co₉S₈@CC) supported on a carbon cloth has been designed and developed to accelerate the sluggish kinetics of the OER. Profiting from valance alternative Ce doping, a fine core–shell structure and vertically aligned nanoneedle arrayed architecture, Ce−Co₉S₈@CC integrates modulated electronic structure, highly exposed active sites, and multidimensional mass diffusion channels; together, these afford a favorable catalyzed OER. Ce−Co₉S₈@CC exhibits remarkable performance in the OER in an alkaline medium, where the overpotential requires only 242 mV to deliver a current density of 10 mA cm⁻² for the OER; this is 70 mV superior to that of Ce-free Co₉S₈ catalyst and other counterparts. Good stability and impressive selectivity (nearly 100 % Faradic efficiency) are also demonstrated. When integrated into a two-electrode OER//HER electrolyzer, the as-prepared Ce−Co₉S₈@CC displays a low operation potential of 1.54 V at 10 mA cm⁻² and long-term stability, thus demonstrating great potential for economical water electrolysis.     

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.     

One-Step Synthesis of NiFe Layered Double Hydroxide Nanosheet Array/N-Doped Graphite Foam Electrodes for Oxygen Evolution Reactions

Developing cost-effective and highly efficient oxygen evolution reaction (OER) electrocatalysts is vital for the production of clean hydrogen by electrocatalytic water splitting. Here, three dimensional nickel-iron layered double hydroxide (NiFe LDH) nanosheet arrays are in-situ fabricated on self-supporting nitrogen doped graphited foam (NGF) via a one-step hydrothermal process under an optimized amount of urea. The as prepared NiFe LDH/NGF electrode exhibits a remarkable activity toward OER with a low onset overpotential of 233 mV and a Tafel slope of 59.4 mV dec⁻¹ as well as a long-term durability. Such good performance is attributed to the synergy among the doping effect, the binder-free characteristic, and the architecture of the nanosheet array.     

Hydrothermal Synthesis and Characterization of a Sandwich-type Tungstophosphate,(1,3-H2dap)8H4[Co4(H2O)2(α-B-PW9O34)2] 2·5H2O

<正>A sandwich-type tungstophosphate, (1,3-H_2dap)_8H_4[Co_4(H_2O)_2(α-B- PW_9O_(34))_2]_2·5H_2O (1,3-dap = 1,3-diaminopropane), was hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, IR and UV spectroscopy. The title compound crystallizes in triclinic, space group P1 with a = 13.691(3), b = 17.744(4), c = 20.620(5), α =113.466(5), β = 91.184(5), γ = 104.223(5)°, V = 4414.3(17)~3, C_(24)H_(96)Co_8N_(16)O_(145)P_4W_(36), M_r = 10143.09, D_c = 3.816 g/cm~3, μ(MoKα) = 24.210 mm~(-1), F(000) = 4452, Z = 1, the final R = 0.0694 and wR = 0.1519 for 9910 observed reflections (I > 2σ(I)). The compound consists of two sets of tetra-transition metal-substituted sandwich frameworks, [Co_4(H_2O)_2(α-B-PW_9O_(34))_2]~(10-) having an inversion centre. Two lacunary α-B-[PW_9O_(34)]~(9-) Keggin units are linked by a rhomb-like Co_4O_(14)(H_2O)_2 cluster, in which the Co~(2+) ions are coordinated by one water molecule. Isolatedly protonated 1,3-H2dap~(2+) units act as counter-ions to interact with the [Co_4(H_2O)_2(α-B-PW_9O_(34))_2]~(10-) heteropolyanions via hydrogen bonds, resulting in a three-dimensional framework.     

LiNi_(0.85)Co_(0.15)O_2合成和结构与电化学性能关系

介绍了一种以LiOH·H_2O, Co_2O_3和Ni_2O_3为原料通过高温法合成LiNi_(0. 85)Co_(0.15)O_2的方法，通过XRD和电化学测试对制得的产物进行了表征，讨论了 合成条件对产物结构的影响以及结构与电化学性能之间的关系。实验结果表明，合 成反应温度、Li/Ni/Co摩尔比对LiNi_(0.85)Co_(0.15)O_2的结构和电化学性能有 较大的影响，合成出具有电化学活性的LiNi_(0.85)Co_(0.15)O_2需要严格控制反 应条件。本文合成出具有高度结晶层状结构的LiNi_(0.85)Co_(0.15)O_2, Rietveld精化结果表明a = 0.2874 nm, c = 1.4229 nm，最大晶胞体积V = 0. 10180 nm~3，其首次放电容量可达197 mA·h/g, 15次循环后，其放电容量仍在 180 mA·h/g以上。     

New strategy to incorporate nano-particle sized water oxidation catalyst into dye-sensitized photoelectrochemical cell for water splitting

In order to develop a new strategy to deposit nano-particle sized water oxidation catalyst based on earth abundant element to the photoanode in a photoelectrochemical cell for water splitting, Co_3O_4 as water oxidation catalyst was prepared and subsequently modified by 3-aminopropyltriethoxysilane. The amino functionalized Co_3O_4 catalyst was carefully characterized and then integrated to the ruthenium dye sensitized photoelectrode through fast Schiff base reaction. Cyclic voltammetry experiments in the dark confirmed that the modified Co_3O_4 catalyst was still active toward water oxidation, which could be initiated by oxidation of the ruthenium photosensitizer. Under visible light irradiation, incorporation of the modified Co_3O_4 catalyst resulted in dramatic enhancement of the transient photocurrent density for the photoanode, which was 8 times higher than that of without Co_3O_4 catalyst.     

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)。     

Co@Co3O4 Encapsulated in Carbon Nanotube‐Grafted Nitrogen‐Doped Carbon Polyhedra as an Advanced Bifunctional Oxygen Electrode

Efficient reversible oxygen electrodes for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are vitally important for various energy conversion devices, such as regenerative fuel cells and metal–air batteries. However, realization of such electrodes is impeded by insufficient activity and instability of electrocatalysts for both water splitting and oxygen reduction. We report highly active bifunctional electrocatalysts for oxygen electrodes comprising core–shell Co@Co₃O₄ nanoparticles embedded in CNT‐grafted N‐doped carbon‐polyhedra obtained by the pyrolysis of cobalt metal–organic framework (ZIF‐67) in a reductive H₂ atmosphere and subsequent controlled oxidative calcination. The catalysts afford 0.85 V reversible overvoltage in 0.1 m KOH, surpassing Pt/C, IrO₂, and RuO₂ and thus ranking them among one of the best non‐precious‐metal electrocatalysts for reversible oxygen electrodes.     

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.     

Facile synthesis of free-standing nickel chalcogenide electrodes for overall water splitting

Developing high-performance noble metal-free and free-standing catalytic electrodes are crucial for overall water splitting. Here, nickel sulfide(Ni_3S_2) and nickel selenide(Ni Se) are synthesized on nickel foam(NF) with a one-pot solvothermal method and directly used as free-standing electrodes for efficiently catalyzing hydrogen evolution reaction(HER) and oxygen evolution reaction(OER) in alkaline solution.In virtue of abundant active sites, the Ni_3S_2/NF and the NiS e/NF electrodes can deliver a current density of 10 m A cm~(-2) at only 123 m V, 137 m V for HER and 222 m V, 271 m V for OER. Both of the hierarchical Ni_3S_2/NF and Ni Se/NF electrodes can serve as anodes and cathodes in electrocatalytic overall watersplitting and can achieve a current density of 10 m A cm~(-2) with an applied voltage of ~1.59 V and 1.69 V,respectively. The performance of as-obtained Ni_3S_2/NF||Ni_3S_2/NF is even close to that of the noble metalbased Pt/C/NF||IrO_2/NF system.     

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.     

Au-Cu/Co3O4双金属催化剂上乙烯完全催化氧化性能

以共沉淀法制得的Co₃O₄为载体, 采用两步法负载Au和Cu制得了一系列Au-Cu/Co₃O₄双金属催化剂, 考察了Au-Cu/Co₃O₄双金属催化剂完全催化氧化乙烯的性能, 并通过X射线衍射(XRD)、高分辨透射电镜(HRTEM)、H₂程序升温还原(H₂-TPR)和O₂程序升温脱附(O₂-TPD)对催化剂进行了表征. 活性测试结果表明: 负载型Au-Cu/Co₃O₄双金属催化剂的催化性能优于单一金属催化剂Au/Co₃O₄, 并且在Au负载量为4% (w, 质量分数)时, 与AuCu/Co₃O₄和Au₃Cu/Co₃O₄催化剂相比, AuCu₃/Co₃O₄催化剂的催化活性较好, 0 ℃时可催化转化15.3%的乙烯为CO₂和H₂O, 120 ℃时100%催化转化乙烯. XRD和HRTEM表明, AuCu₃/Co₃O₄催化剂中有Au-Cu合金相的生成, 而Au₃Cu/Co₃O₄催化剂中Cu主要以氧化物的形式存在. Au和Cu之间产生相互作用, 使活性相金属的粒径降低. H₂-TPR和O₂-TPD分析结果表明, AuCu₃/Co₃O₄催化剂具有较强的低温可还原能力和可提供的大量表面活性吸附氧物种, 促进了乙烯的完全催化氧化.