Nanostructured energy materials for electrochemical energy conversion and storage: A review

Nanostructured materials have received tremendous interest due to their unique mechanical/electrical properties and overall behavior contributed by the complex synergy of bulk and interfacial properties for efficient and effective energy conversion and storage. The booming development of nanotechnology affords emerging but effective tools in designing advanced energy material. We reviewed the significant progress and dominated nanostructured energy materials in electrochemical energy conversion and storage devices, including lithium ion batteries, lithium–sulfur batteries, lithium–oxygen batteries, lithium metal batteries, and supercapacitors. The use of nanostructured electrocatalyst for effective electrocatalysis in oxygen reduction and oxygen evolution reactions for fuel cells and metal–air batteries was also included. The challenges in the undesirable side reactions between electrolytes and electrode due to high electrode/electrolyte contact area, low volumetric energy density of electrode owing to low tap density,and uniform production of complex energy materials in working devices should be overcome to fully demonstrate the advanced energy nanostructures for electrochemical energy conversion and storage. The energy chemistry at the interfaces of nanostructured electrode/electrolyte is highly expected to guide the rational design and full demonstration of energy materials in a working device.     

Valence modulated nickel oxynitride network as integrated bifunctional electrodes for enhanced energy storage

As promising electrode materials,transition metal oxides have attracted considerable attention owing to their excellent performance in electrochemical energy storage.However,their poor conductivity and fragile structure limit their practical application.In this study,a binder-free nickel oxide/oxynitride network(NiON WS)bifunctional electrodes with cation multivalent states that exhibit high energy storage performance were synthesized for the first time.The massive active sites,high specific surface areas,and multiple cation valence states of NiON WS were advantageous for electrochemical redox reaction during its application in supercapacitors(1283.5 mF cm^-2)and lithium-ion batteries(1345.0 mA h g^-1).Particularly,the NiON WS based flexible asymmetric SCs exhibit excellent capacitance and energy densities.First-principle calculations were employed to study the mechanism of the electrochemical performance improvement of NiON WS.This study demonstrates the potential of transition metal oxides electrode with high capacity and activity for electrochemical energy storage and conversion.     

Coupling of methane under pulse corona plasma (Ⅰ)——In the absence of oxygen

At normal temperature and pressure, pulse corona plasma was used as a new method for the dehydrogenative coupling of methane in the absence of oxygen. The effects of voltage polarity and input energy on the dehydrogenative coupling of methane were investigated. The parameter "energy efficiency" was introduced to examine the coupling of the input energy and the dehydrogenative coupling of methane. The experimental results show that positive corona gives higher energy efficiency than negative corona. When the positive corona was chosen, C2. yield per pass was 31.6% and acetylene yield per pass was 30.1% with 44.6% methane conversion at an input energy density of 1788kJ/mol and a pulse repetition frequency of 66Hz. The function of input energy density towards methane conversion may be expressed as a formula of -ln(1-X) = k (P/F). In the range of input energy employed, C2 yield is proportional to input energy density, but energy efficiency drops off with increasing input energy density.     

Facile Synthesis of Layered Sodium Manganese Oxide for Application in Asymmetric Supercapacitor

Layered sodium manganese oxides(LSMOs), with two-dimensional channels for ion diffusion, have been regarded as the promising electrode materials in the application of asymmetric supercapacitors(ASCs). In this work, the layered Na_(0.5)Mn_2O_4·1.5H_2O was synthesized through a facile hydrothermal method by controlling the molar ratio of sodium and manganese. When the molar ratio of sodium to manganese is 3:1, Na_(0.5)Mn_2O_4·1.5H_2O has shown the best capacitance of 369 F/g with current density of 0.5 A/g, and maintained a capacitance of 265 F/g after 2000 cycles. The asymmetric supercapacitor consists of the sodium manages oxides as the positive electrode and active carbon(AC) as the negative electrode in 1 mol/L Na_2SO_4 solution. The voltage of the asymmetric supercapacitor has been expanded to 0～2 V with an energy density of 10.13 Wh/kg at a power density of 500 W/kg based on the total weight of both active electrode materials when the mass ratio of AC to Na_(0.5)Mn_2O4·1.5H_2O was 3:1.     

Performance of PbO2/activated carbon hybrid supercapacitor with carbon foam substrate

PbO₂/activated carbon（AC） hybrid supercapacitor in H₂SO₄ with a carbon foam current collector is studied.The PbO₂/AC hybrid is designed with electrodeposited PbO₂ thin film as positive electrode to match with AC negative electrode.The discharge curve shows capacitive characteristics between 1.88 V and 0.65 V.The hybrid system exhibits excellent energy and power performance,with specific energy of 43.6 Wh/kg at a power density of 654.2 W/kg.The use of carbon foam current collector ensures stability of the PbO₂ electrode in H₂SO₄ environment.After 2600 deep cycles at 15 C high rate of charge/discharge,the capacity remains nearly unchanged from its initial value.     

Pt-MoOx/CNT电极的制备及其对乙醇氧化电催化性能研究

MoOx,a non-noble secondary catalyst instead of noble metal Ru,was dispersed on carbon nanotubes(CNT)andthen the primary catalyst Pt was electrodeposited on MoO_x/CNT/graphite electrode by potential-step method.CNTused was grown directly on graphite disk by chemical vapor deposition.The Pt-MoO_x/CNT/graphite electrode wascharacterized by scanning electron microscopy and energy dispersive X-ray spectroscopy.The electrocatalyticproperty and the long-term cyclic stability of Pt-MoO_x/CNT/graphite electrode for ethanol oxidation have been in-vestigated in 1.0 mol/L CH_3CH_2OH 0.1 mol/L H_2SO_4 by cyclic voltammetry.On the other hand,the effect of theloading mass of MoO_x on specific activity of Pt-MoO_x/CNT/graphite electrode and the activation energy of ethanoloxidation were investigated.The Pt-MoO_x/CNT/graphite electrode shows good long-term cyclic stability.82%value of peak current density at the oxidation peak around 0.69 V(vs.SCE)remains after 500 cycles,which ishigher than those of Pt/CNT/graphite and Pt-Ru/CNT/graphite electrodes with the corresponding values of 55% and72%,respectively.     

Unraveling and optimizing the metal-metal oxide synergistic effect in a highly active Cox(CoO)1–x catalyst for CO2 hydrogenation

The relation between catalytic reactivities and metal/metal oxide ratios, as well as the functions of the metal and the metal oxides were investigated in the CO_2 hydrogenation reaction over highly active Co_x(CoO)_1–xcatalysts in operando. The catalytic reactivity of the samples in the CO_2 methanation improves with the increased Co O concentration. Strikingly, the sample with the highest concentration of CoO, i.e., Co_0.2(CoO)_0.8, shows activity at temperatures lower than 200 °C where the other samples with less CoO are inactive. The origins of this improvement are the increased amount and moderate binding of adsorbed CO_2 on CoO sites. The derivative adsorption species are found to be intermediates of the CH4 formation. The metallic Co functions as the electronically catalytic site which provides electrons for the hydrogenation steps. As a result, an abundant amount of CoO combined with Co is the optimal composition of the catalyst for achieving the highest reactivity for CO_2 hydrogenation.     

Charge transfer across the water/nitrobenzene interface by three-electrode system

A droplet of aqueous solution containing a certain molar ratio of redox couple is first attached onto a platinum electrode surface, then the resulting drop electrode is immersed into the organic solution containing very hydrophobic electrolyte. Combined with reference and counter electrodes, a classical three-electrode system has been constructed. Ion transfer (IT) and electron transfer (ET) are investigated systematically using three-electrode voltammetry. Potassium ion transfer and electron transfer between potassium ferricyanide in the aqueous phase and ferrocene in nitrobenzene are observed with potassium ferricyanide/potassium ferrocyanide as the redox couple. Meanwhile, the transfer reactions of lithium, sodium, potassium, proton and ammonium ions are obtained with ferric sulfate/ferrous sulfate as the redox couple. The formal transfer potentials and the standard Gibbs transfer energy of these ions are evaluated and consistent with the results obtained by a four-electrode system and other methods.     

TiO_2-Supported Binary Metal Oxide Catalysts for Low-temperature Selective Catalytic Reduction of NO_x with NH_3

Binary metal oxide（MnOx-A/TiO2）catalysts were prepared by adding the second metal to manganese oxides supported on titanium dioxide（TiO2）,where,A indicates Fe2O3,WO3,MoO3,and Cr2O3.Their catalytic activity,N2 selectivity,and SO2 poisonous tolerance were investigated.The catalytic performance at low temperatures decreased in the following order：Mn-W/TiO2〉Mn-Fe/TiO2〉Mn-Cr/TiO2〉Mn-Mo/TiO2,whereas the N2 selectivity decreased in the order：Mn-Fe/TiO2〉Mn-W/TiO2〉Mn-Mo/TiO2〉Mn-Cr/TiO2.In the presence of 0.01%SO2 and 6%H2O,the NOx conversions in the presence of Mn-W/TiO2,Mn-Fe/TiO2,or Mn-Mo/TiO2 maintain 98.5%,95.8%and 94.2%, respectively,after 8 h at 120°C at GHSV 12600 h？ 1 .As effective promoters,WO3 and Fe2O3 can increase N2 selectivity and the resistance to SO2 of MnOx/TiO2 significantly.The Fourier transform infrared（FTIR）spectra of NH3 over WO3 show the presence of Lewis acid sites.The results suggest that WO3 is the best promoter of MnOx/TiO2,and Mn-W/TiO2 is one of the most active catalysts for the low temperature selective catalytic reduction of NO with NH3.     

Ni3S2 nanorods growing directly on Ni foam for all-solid-state asymmetric supercapacitor and efficient overall water splitting

Transition metal compounds are attractive for their significant applications in supercapacitors and as non-noble metal catalysts for electrochemical water splitting.Herein,we develop Ni3 S2 nanorods growing directly on Ni foam,which act as multifunctional additive-free Ni3 S2@Ni electrode for supercapacitor and overall water splitting.Based on PVA-KOH gel electrolyte,the assembled all-solid-state Ni3 S2@Ni//AC asymmetric supercapacitor delivers a high areal energy density of 0.52 mWh cm^-2 at an areal power density of 9.02 MW cm^-2,and exhibits an excellent cycling stability with a capacitance retention ratio of 89%after 10000 GCD cycles at a current density of 30 mA cm^-2.For hydrogen evolution reaction and oxygen evolution reaction in 1 M KOH,Ni3 S2@Ni electrode achieves a benchmark of 10 mA cm^-2at overpotentials of 82 mV and 310 mV,respectively.Furthermore,the assembled Ni3 S2@Ni‖Ni3 S2@Ni electrolyzer for overall water splitting attains a current density of 10 mA cm^-2 at 1.61 V.The in-situ synthesis of Ni3 S2@Ni electrode enriches the applications of additive-free transition metal compounds in high-performance energy storage devices and efficient electrocatalysis.     

Novel Catalytic Dielectric Barrier Discharge Reactor for Gas-Phase Abatement of Isopropanol

Catalytic gas-phase abatement of air containing 250 ppm of isopropanol (IPA) was carried out with a novel dielectric barrier discharge (DBD) reactor with the inner catalytic electrode made of sintered metal fibers (SMF). The optimization of the reactor performance was carried out by varying the voltage from 12.5 to 22.5 kV and the frequency in the range 200–275 Hz. The performance was significantly improved by modifying SMF with Mn and Co oxide. Under the experimental conditions used, the MnO _x /SMF showed a higher activity towards total oxidation of IPA as compared to CoO _x /SMF and SMF electrodes. The complete destruction of 250 ppm of IPA was attained with a specific input energy of ∼235 J/L using the MnO _x /SMF catalytic electrode, whereas, the total oxidation was achieved at 760 J/L. The better performance of the MnO _x /SMF compared to other catalytic electrodes suggests the formation of short-lived active species on its surface by the in-situ decomposition of ozone.     

静电纺氧化锰复合碳纳米纤维柔性膜的电化学性能

采用一步法静电纺丝技术制备了具有超亲水特性的氧化锰/碳纳米纤维(MnO_x/CNFs)复合柔性膜电极材料,并通过X射线衍射、扫描电子显微镜和透射电子显微镜等对复合材料进行了表征.电化学性能测试结果表明,复合材料的电容性能优于单一材料,醋酸锰质量分数为40%时制得的复合纳米纤维电极(MC-4)在1 A/g电流密度下,于2 mol/L KOH电解液中的比电容高达1112.5 F/g,10 A/g电流密度下循环3000次比容量保持在93.4%,具有很好的稳定性.MnO_x/CNFs复合材料电化学性能增强一方面是由于三维超亲水纤维膜结构有利于电解液的快速浸润渗透,从而极大缩短了传输到材料基质的有效路径;另一方面是由于碳和MnO_x的协同效应,包裹在MnO_x粒子周围的碳层避免了MnO_x在充放电过程中的体积膨胀效应,这2种叠加机制促进了电化学性能的提升.     

Fabrication of an Electrochemical L‐Cysteine Sensor Based on Graphene Nanosheets Decorated Manganese Oxide Nanocomposite Modified Glassy Carbon Electrode

The graphene nanosheets/manganese oxide nanoparticles modified glassy carbon electrode (GC/GNSs/MnOx) was simply prepared by casting a thin film of GNSs on the GC electrode surface, followed by performing electrodeposition of MnOx at applied constant potential. The GC/GNSs/MnOx modified electrode shows high catalytic activity toward oxidation of L ‐cysteine. Hydrodynamic amperometry determination of L ‐cysteine gave linear responses over a concentration range up to 120 µM with a detection limit of 75 nM and sensitivity of 27 nA µM^?1. The GC/GNSs/MnOx electrode appears to be a highly efficient platform for the development of sensitive, stable and reproducible L ‐cysteine electrochemical sensors.     

The Solid-State-Grinding Synthesis of Maganese-Modified Cobalt Oxides and Application in the Low-Temperature CO Preferential Oxidation in H<Subscript>2</Subscript>-Rich Gases

A series of MnOx modified cobalt oxides with different atomic molar ratios of Mn/(Mn?+?Co) were prepared by a soft reactive grinding route and investigated for CO preferential oxidation in H₂. It was found that as-prepared Mn-doped cobalt oxides exhibited superior activity compared to the single constituted oxides, other Mn–Co–O mixed oxides synthesized by solution-based route, and other grinding-derived mixed metal oxides M–Co–O (M?=?Zn, Ni, Cu, Fe). The grinding-derived MnCo10 catalyst with Mn/(Mn?+?Co) molar ration of 10% showed the best CO oxidation activity and higher selectivity at low temperature. The surface richness of Co³⁺ was not found as increasing the Mn molar ratio in the present work. However, the incoporation of MnOx with proper amount into Co₃O₄ could produce high surface area, high structure defects, and rich surface active oxygen species, while the ability to supply the active oxygen species was suggested to play the crucial role in promoting the catalytic performance of Mn–Co–O mixed oxides.     

Recent advances in metal oxide/hydroxide on three-dimensional nickel foam substrate for high performance pseudocapacitive electrodes

The high demand for long-lasting and portable energy storage devices with enhanced energy and power densities has attracted researcher's interest globally. The three-dimensional (3D) nickel foam is a promising electrode material for storing energy in various devices because they possess large surface area, are very conductive and enjoy a continuous permeable 3D system. This article provides a review and detailed information on the uses of 3D nickel foam-based electrodes with metal oxides/hydroxides of different morphologies for high-performance pseudocapacitors. We assess the limitations and future prospects of 3D nickel foam-based electrodes with metal oxides/hydroxides for industrial application towards enhancing pseudocapacitors' energy storage capability.     

Synthesis and characterization of carbon-supported transition metal oxide nanoparticles — Cobalt porphyrin as catalysts for electroreduction of oxygen in acids

Unpyrolyzed, non noble metal catalysts for Oxygen Reduction Reaction (ORR), denoted MeOx–CoP/C, were obtained using a two-step procedure. The procedure consisted of a synthesis of carbon-supported transition metal (Me═Co, or Ni, or Fe) nanoparticles, followed by adsorption of cobalt porphyrin (CoP). TEM and XPS analyses confirm the formation of nanoparticles and the presence of transition metal oxides. Rotating disk electrode measurements showed that the as-synthesized materials exhibit catalytic ORR activity in acidic medium toward oxygen reduction, which is higher than that of cobalt porphyrin on carbon. This reveals that the metal oxide nanoparticles enhance the activity of the metalloporphyrin without being electroactive themselves. The catalytic activity follows the sequence: CoOx–CoP/C > NiOx–CoP/C > FeOx–CoP/C, showing the influence of nature of the transition metal on the enhancing effect. The presence of a cobalt center incorporated in the macrocycle was found to be essential to the oxygen reduction reaction, appearing thus to be the catalytic active site of the reaction. Our data suggest the ORR occurs at a single active site.     

Surfactant-assisted hydrothermal synthesis of CoMn2O4 nanostructures for efficient supercapacitors

Journal of Solid State Electrochemistry - Mixed transition metal oxides/spinels are excellent energy storage electrode materials that can deliver sizeable specific capacitance, excellent cyclic...     

金属氧化物电化学电容器

电化学电容器是一类利用电化学双电层或电极材料在电极表面及体相发生的氧化还原反应而存储能量的装置，具有高比能量、良好的可逆性和长循环寿命。金属氧化物电极目前主要有贵金属氧化物和过渡金属氧化物。本文简要介绍了金属氧化物电化学电容器的储能机理、特点及应用，总结了电极材料的制备及改性方法；并简要评述了电极材料的研究进展。     

高效 CeO2-MnOx-Al2O3催化剂的制备、表征及催化消除 NO性能

机动车在给人类生活带来便利的同时,也造成了严重的大气污染.其尾气净化成为人们关注的焦点.一氧化氮(NO)、一氧化碳(CO)和碳氢化合物(HCs)是机动车尾气中的三大典型污染物,主要通过三效催化(TWC)技术进行脱除. TWC技术涉及几个重要的催化反应,其中 CO催化还原 NO由于能够同时消除 CO和 NO两种污染物而引起研究者的极大关注.研究表明,负载型贵金属催化剂在该反应中显示出优异的催化性能,但存在资源匮乏、价格昂贵以及热稳定性欠佳等不足.因此,低价、高效的过渡金属氧化物催化剂成为近年研究重点.稀土金属氧化物 CeO2由于具有良好的氧化还原性能、较高的储释氧容量以及丰富的表面氧空位而被广泛用于 CO催化还原 NO反应.研究表明,对 CeO2进行离子掺杂可进一步增大其比表面积,改善其氧化还原性能和储释氧容量.并且,我们在先前的研究中还发现,将具有多种可变价态的钛离子或锡离子掺入 CeO2晶格由于掺杂离子能与 Ce4+/Ce3+发生电子转移而更有利于改善 CeO2的理化性质.此外,锰氧化物(MnOx)在氧化还原气氛中容易实现不同价态之间的切换,从而在一些重要的氧化还原反应中表现出优异的催化性能.近年来,有研究者将 CeO2与 MnOx相结合制备了 CeO2-MnOx催化剂用于 NO消除、碳烟燃烧和挥发性有机物(VOCs)氧化等反应,并取得一些有意义的结果.然而,对于实际应用来说, CeO2-MnOx催化剂存在比表面积偏小等不足.众所周知,γ-Al2O3是一种常用的具有高比表面积和高热稳定性的催化剂载体材料,可有效增大催化剂比表面积.我们前期研究结果表明,通过共沉淀法将 Al3+掺入铈基复合氧化物的晶格相比于以γ-Al2O3为载体更有利于改善铈基复合氧化物的理化性质和催化性能.因此,我们通过简单的氨水反滴加共沉淀法制备了一系列 CeO2-MnOx-Al2O3(Ce：Mn：Al摩尔比=6：4：x,x =0.25,0.5,1,2)复合氧化物催化剂用于 CO催化还原 NO反应.并运用 X射线衍射、拉曼光谱、氮气物理吸附、氢气程序升温还原、X射线光电子能谱以及原位漫反射红外光谱等表征技术对上述催化剂进行了系统分析.重点考察了 Al3+掺杂量对 CeO2-MnOx-Al2O3复合氧化物催化剂理化性质和催化性能的影响.结果表明,在 CeO2-MnOx复合氧化物中掺入少量 Al3+会导致其晶粒尺寸减小,从而增大其比表面积和孔体积,并增加 Ce3+和 Mn4+的含量.比表面积和孔体积增大有助于催化剂与反应物分子之间充分接触; Ce3+和 Mn4+含量增加能分别促进 CO物种吸附以及吸附态 NO物种脱附、转化和解离.这些变化有利于提高 CeO2-MnOx复合氧化物在 CO催化还原 NO反应中的催化性能.最后,基于催化剂的理化性质表征及其催化性能评价,我们尝试提出了一个可能的催化反应机理,以进一步理解 CeO2-MnOx-Al2O3复合氧化物催化剂在 CO催化还原 NO反应中的优异性能.