Silver nanoparticles embedded phosphomolybdate–polyaniline hybrid electrode for electrocatalytic reduction of H<Subscript>2</Subscript>O<Subscript>2</Subscript>

Hybrid silver/phosphophomolybdate/polyaniline (Ag/PMo12/PAni) was obtained through one pot synthesis, and then, it was successfully fabricated on the glassy carbon electrode by simple casting method for electrocatalytic reduction of hydrogen peroxide (H₂O₂). The cyclic voltammetric studies of the Ag/PMo12/PAni hybrid electrode suggest that the electronic properties of the phosphomolybdate are retained even after the formation of hybrid material and in addition effectively electro-catalyzing the reduction of H₂O₂ with a less negative over potential. The Ag/PMo12/PAni-modified electrode showed the lowest detection limit (750 nM) for H₂O₂ reduction among the hybrid-modified electrodes already reported with a sensitivity of 4.398 nA μM⁻¹. The prepared hybrid material was well characterized by using UV, XRD and TEM analysis.     

An overview on the recent developments in polyaniline‐based supercapacitors

With the ever‐increasing depletion of nonrenewable fossil fuel reserve, greater attention has been directed towards renewable energy storage devices. One of the most important of such devices is the supercapacitor, which exhibits high specific capacitance. Polyaniline (PAni) is a versatile conducting polymer, which has demonstrated excellent electrochemical properties along with good stability and ease of synthesis. Therefore, PAni has been extensively used in the fabrication of supercapacitors. In the last few decades, researchers have studied the effect of morphology, developed during the synthesis of PAni, on its electrochemical properties. It is known that the electrical conductivity and the electrochemical properties of PAni get influenced by the level and type of dopant used, the method of synthesis adopted, and the surface area and porosity possessed. However, it has been realized that supercapacitors based on PAni suffer from short cycle life. This led to development of PAni composites with carbon‐based materials and transition metal oxides. In this review, focus has been laid on the achieved performance levels of the recently developed PAni‐based supercapacitors. In addition, an attempt has been made to study the fundamental aspects of the conductivity and the electrochemical properties of PAni and their effect on the supercapacitor performance. Moreover, several new interesting applications of PAni‐based supercapacitors have also been included in this review.     

In Situ Electrochemical Production of Metal-organic Hybrid Composite Film from Nickel Containing Polyoxometalate and 3,4-Ethylenedioxy-thiophene for Sensor Application

In situ electrochemical synthesis of an organic-inorganic hybrid material composed of poly(3,4-ethylenedioxythiophene) (PEDOT) and nickel-based Keggin type polyoxometalate, K₇[Ni^IIINi^II(H₂O)W₁₁O₃₉].15H₂O(NiPOM), has been proposed here. The remarkable optical and electrical properties of the PEDOT and the unique redox properties of NiPOM have synergistically combined to make the hybrid structure highly desired multi-functional materials for a myriad of applications. The driving force for the formation of hybrid structure is thought to be electrostatic interactions between POM anions and cationic polaron/bipolaron structures that in the PEDOT. PEDOT/NiPOM based hybrid composite modified graphite electrode has been used for non-enzymatic glucose sensor platform as a sample of applications. Furthermore, PEDOT/NiPOM based sensor platform was successfully utilized for detection of glucose content with the lowest detection limit in real samples like honey and milk. These results suggest that PEDOT/NiPOM metal-organic hybrid composite could be utilized as multi-functional material for a myriad of applications.     

In situ synthesized heteropoly acid/polyaniline/graphene nanocomposites to simultaneously boost both double layer- and pseudo-capacitance for supercapacitors

It is challenging to simultaneously increase double layer- and pseudo-capacitance for supercapacitors. Phosphomolybdic acid/polyaniline/graphene nanocomposites (PMo(12)-PANI/GS) were prepared by using PMo(12) as a bifunctional reagent for not only well dispersing graphene for high electrochemical double layer capacitance but also in situ chemically polymerizing aniline for high pseudocapacitance, resulting in a specific capacitance of 587 F g(-1), which is ～1.5 and 6 times higher than that of PANI/GS (392 F g(-1)) and GS (103 F g(-1)), respectively. The nanocomposites also exhibit good reversibility and stability. Other kinds of heteropolyacids such as molybdovanadophosphoric acids (PMo(12-x)V(x), x = 1, 2 and 3) were also used to prepare PMo(12-x)V(x)-PANI/GS nanocomposites, also showing enhanced double layer- and pseudo-capacitance. This further proves the proposed concept to simultaneously boost both double layer- and pseudo-capacitance and demonstrates that it could be a universal approach to significantly improve the capacitance for supercapacitors.     

Self-sustaining hybrid electrode prepared from polyaniline,carbon nanotubes,and carbon fibers: morphological,structural, and electrochemical analyses

The self-sustaining hybrid electrode was prepared via chemical polymerization of aniline in acid medium containing dispersed carbon nanotubes (CNT), using carbon fiber (CF) as conducting substrate. The ternary composites called PAni/CNT/CF were characterized in order to evaluate their morphologies, structures, and thermal properties. The influence of the polyaniline (PAni) layer in the ternary composite properties was studied considering different deposition times on CF samples (30, 60, and 90 min). The ternary composite morphologies were observed by scanning electron microscopy while thermal structural analyses were obtained using thermogravimetric measurements. The structural features were analyzed by Raman scattering spectroscopy and Fourier transform infrared spectroscopy (FTIR). The possible interactions between PAni and CNT were discussed on the basis of Raman and FTIR spectra. These spectroscopic analyses also confirmed that the PAni present in the composite is in the emeraldine (ES) salt form. Furthermore, the ternary composites were also evaluated by electrochemical measurements such as cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) techniques. The results showed good charge storage capacity for ternary composites, in particular, for PAni/CNT/CF obtained with 90 min of deposition time, which exhibited specific capacitance of around 500 F g^?1. Therefore, this electrode was selected to build a prototype of type I supercapacitor. This device presented specific capacitance of around 143 F g^?1 after 3200 charge/discharge cycles.     

纳米材料在超级电容器领域的有效设计与可控合成

伴随着电化学储能器件在便携式电子产品、混合动力电动汽车及大型工业规模的电力和能源管理中的应用,设计合成出结构新颖、性能优越的先进纳米电极材料显得至关重要.作为电化学储能器件中的重要一员,超级电容器以其功率密度高、循环寿命长等特点越来越受到人们的广泛关注,而电极材料的组成及结构是其性能高低的决定性因素.本文结合本科研团队近几年来的研究工作,综述了有关超级电容器纳米电极材料的设计与可控合成及其前沿研究进展.     

Plasma enhanced synthesis of N doped vertically aligned carbon nanofibers on 3D graphene

Graphene and carbon nanotubes/fibers (CNT/CNF) hybrid structures are emerging as frontier materials for high-efficiency electronics, energy storage, thermoelectric, and sensing applications owing to the utilization of extraordinary electrical and physical properties of both nanocarbon materials. Recent advances show a successful improvement in the structure and surface area of layered graphene by incorporating another dimension and structural form—three-dimensional graphene (3DG). In this study, vertically aligned CNFs were grown using plasma enhanced chemical vapor deposition on a relatively new form of compressed 3DG. The latter was synthesized using a conventional thermal chemical vapor deposition. The resulting free-standing hybrid material is in-situ N doped during synthesis by ammonia plasma and is produced in the form of a hybrid paper. Characterization of this material was done using electrochemical and spectroscopic measurements. The N doped hybrid showed relatively higher surface area and improved areal current density in electrochemical measurements than compressed pristine 3DG, which makes it a potential candidate for use as an electrode material for supercapacitors, sensors, and electrochemical batteries.     

溶剂热法合成UiO-66金属有机框架限域的钴取代磷钼酸及其催化烯烃环氧化性能

金属有机框架材料是一类新型晶体孔性材料,在气体储存、物质分离、非线性光学及催化等领域中具有潜在应用价值.其中,基于锆氧簇和有机配体构筑的锆基金属有机框架材料(ZrMOFs)因其具有更高的结构稳定性而备受关注.研究表明,将多金属氧酸盐(POM)负载在ZrMOFs载体上能够获得一类新型复合材料催化剂.这类材料具有可调控的酸性和氧化还原性,已在一些固体酸催化及选择氧化(包括烯烃环氧化)等反应中表现出优异的催化性能.多金属氧酸盐通常可以通过简单的浸渍法引入到ZrMOFs载体上,但这种方法制备的催化剂普遍存在活性组分分散不均匀且易于在液相催化反应过程中发生活性组分流失的问题.因此,当前的研究重点主要集中在如何通过简单有效的制备方法获得结构更加稳定、性能更加优异的复合材料催化剂.近期,国内外多个研究小组分别报道了采用溶剂热法能够一步合成出POM@ZrMOFs复合材料,这类材料的主要特点是POM团簇能够均匀的分散在ZrMOFs孔道中,从而使其在氧化脱硫及烯烃选择氧化等反应中表现出更高的稳定性.考虑到POMs及ZrMOFs种类和结构的多样性,可以预期这类复合材料的合成及催化性能研究仍有很大的发展空间.本文采用溶剂热法将磷钼酸(PMo12)及钴取代磷钼酸(PMo11Co)限域在一类ZrMOFs材料(UiO-66)的孔道中,得到了两种复合材料催化剂,分别记为PMo12@UiO-66和PMo11Co@UiO-66.通过以叔丁基过氧化氢(t-BuOOH)为氧化剂烯烃环氧化反应考察了其催化性能.相较于PMo12@UiO-66,含有钴取代磷钼酸的PMo11Co@UiO-66杂化材料表现出了更高的催化活性和稳定性.催化剂经简单的过滤和洗涤后即可循环使用多次,且催化性能基本保持不变.值得一提的是,PMo11Co@UiO-66对多种类型烯烃的环氧化反应均表现出较高的催化活性和环氧选择性.例如,在加入自由基抑制剂对二苯酚后,柠檬烯选择性氧化为柠檬烯-1,2-环氧化物的选择性可以达到91%,性能明显优于文献中报道的其它类型催化剂.此外,溶剂种类对PMo11Co@UiO-66的催化活性有着显著的影响,在极性相对较强的乙醇、乙腈等溶剂中,催化剂的活性较低;在极性较弱的甲苯、氯仿,四氯化碳等溶剂中,催化剂的活性则相对较高.溶剂极性的差异会影响反应物分子与催化剂活性中心的接触情况,继而对催化剂的活性产生较大影响.采用X射线衍射、氮吸附-脱附、X射线光电子能谱、傅立叶变换红外光谱(FT-IR)等手段对催化反应前后的PMo11Co@UiO-66催化剂进行了表征.结果表明,在溶剂热法合成的杂化材料催化剂中,引入的POM团簇能够均匀的分散在UiO-66框架材料的孔道和笼中;催化剂反应前后的组成与结构没有发生明显的变化.结合相关文献报道的结果,可以认为杂原子Co的引入能够产生类似于Co–O–Mo的新的活性中心,从而使PMo11Co@UiO-66表现出更高的催化活性.催化剂的高稳定性应主要归因于UiO-66框架对PMo11Co团簇的空间限域作用.这种空间限域作用能够使PMo11Co团簇被封装在UiO-66的八面体笼中,且二者之间还存在着较强的金属-载体间相互作用.在后续的工作中,我们还将继续深入研究PMo11Co@UiO-66催化剂的活性中心性质及其对分子氧的活化能力,加深对催化作用机制等问题的理解,进一步扩大这类复合材料催化剂的应用范围.     

Nickel/cobalt based materials for supercapacitors

We briefly summarize the fundamental mechanism of supercapacitors and classify them into three kinds according to the different energy storage mechanism. We further discuss the energy storage mechanism of nickel/cobalt based materials, and we suggest that these kinds of battery-type materials should be classified into hybrid supercapacitor instead of pseudocapacitors.     

Synthesis of Robust MOFs@COFs Porous Hybrid Materials via an Aza-Diels–Alder Reaction: Towards High-Performance Supercapacitor Materials

Metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) have attracted enormous attention in recent years. Recently, MOF@COF are emerging as hybrid architectures combining the unique features of the individual components to enable the generation of materials displaying novel physicochemical properties. Herein we report an unprecedented use of aza-Diels–Alder cycloaddition reaction as post-synthetic modification of MOF@COF-LZU1, to generate aza-MOFs@COFs hybrid porous materials with extended π-delocalization. A a proof-of-concept, the obtained aza-MOFs@COFs is used as electrode in supercapacitors displaying specific capacitance of 20.35 μF cm⁻² and high volumetric energy density of 1.16 F cm⁻³. Our approach of post-synthetic modification of MOFs@COFs hybrids implement rational design for the synthesis of functional porous materials and expands the plethora of promising application of MOFs@COFs hybrid porous materials in energy storage applications.     

New materials based on the reaction of cyclo- and poly-(organo phosphazenes) with SiO2, TiO2 and ZrO2 precursors

A new class of organic-inorganic materials can be prepared, based on inorganic networks and cycloor poly-(organophosphazenes). Poly(organophosphazenes) are polymers characterized by many interesting technological properties. This report is based on a investigation on the reactivity of SiO₂, TiO₂ and ZrO₂ precursors with different phosphazene compounds functionalized with hydroxyl groups, to prepare materials with a hybrid structure. The synthesis of these systems was studied in different experimental conditions. Evidences on the structures and properties of these materials will be presented on the basis of FTIR, SEM and thermal analysis characterization results.     

Designed synthesis of ZnO/PEDOT core/shell hybrid nanotube arrays with enhanced electrochromic properties

Designed growth of zinc oxide (ZnO)/poly(3,4-ethylenedioxythiophene) (PEDOT) core/shell hybrid nanotube arrays has been achieved by electropolymerization technique. The ZnO/PEDOT hybrid nanotubes electropolymerized for 2000-second display enhanced electrochromic properties of the contrast ratio up to 31.3%, a lot higher than those of the pure PEDOT and ZnO/PEDOT hybrid nanorods. Moreover, the coloring efficiency of the hybrid nanotubes increases from 105.2 cm² C⁻¹ of ZnO/PEDOT hybrid nantotube with the electrodeposition time of 1000 seconds to 122.2 cm² C⁻¹ of 2000 seconds at 520 nm. Therefore, the hybrid composite nanotubes fabricated by the in situ electrodeposition techniques may demonstrate huge potential applications in energy-saving technologies such as smart windows.     

Improving the fabrication of all-polythiophene supercapacitors

The influence of the preparation method in the properties of poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes used to manufacture organic energy storage devices, as for example supercapacitors, have been examined by considering a reduction of both monomer and supporting electrolyte concentrations during the anodic polymerization reaction. Thus, the excellent electrochemical properties of PEDOT films prepared using quiescent solutions have been preserved by applying controlled agitation to the polymerization process, even though the concentration of monomer and supporting electrolyte were reduced 5 and 2 times, respectively. For example, the charge stored for reversible exchange in a redox process, the electrochemical stability and the current productivity of films achieved using quiescent solutions have been preserved using a dynamic reaction medium in which the concentrations of monomer and supporting electrolyte are several times lower. The excellent properties of PEDOT electrodes prepared using optimized dynamic conditions have also been proved by constructing a symmetric supercapacitor. This energy storage device, which has been used as power source for a LED bulb, is rechargeable and exhibits higher charge-discharge capacities than supercapacitors prepared with electrodes derived from quiescent solutions. In addition of bring an efficacious procedure for preparing cost-effective PEDOT films with excellent properties, the proposed dynamic conditions reduce the environmental hazards of depleted reaction media.     

Electrochemistry of Electrode Materials Containing S−Se Bonds for Rechargeable Batteries

Sulfur (S) and selenium (Se) have been considered as promising high capacity cathode materials for rechargeable batteries. They have differences in their physical properties (e.g., electronic conductivity) but the same number of electrons in their outermost shells, which leads to similarity in their electrochemical behavior in batteries. In recent years, some efforts have been taken to combine them in electrodes in the hope of improved battery performance. The S−Se bonds of these electrode materials lead to unusual properties and intriguing electrochemical behavior, which have attracted increasing interest. In this Minireview, electrode materials containing S−Se bonds are summarized, including inorganic S_xSe_y solid solutions, organic compounds, and organic–inorganic hybrid materials. Our understanding in these materials is still premature, but they have shown unique properties to be electrode materials. We hope this Minireview could provide a new insight into the design, synthesis, and understanding of these materials, which could enable high energy density rechargeable batteries.     

Preparation of activated carbon from Turbinaria turbinata seaweeds and its use as supercapacitor electrode materials

Turbinaria turbinata brown seaweeds were tested as carbon electrode material in symmetric, electrochemical supercapacitors. The electrochemical properties of the carbon materials were characterised for their application as supercapacitors using cyclic voltammetry, galvanostatic charge/discharge method and electrochemical impedance spectroscopic analyses. Our initial results showed that the optimal behaviour was obtained for the sample prepared by pyrolysis at 800 °C. The average surface area of the carbon was 812 m²/g. Electrochemical tests with an organic electrolyte gave the following interesting results: a capacitance of 74.5 F/g, a specific series resistance of 0.5 Ω cm² and an ionic resistivity of 1.3 Ω cm². These results show the promising capacitive properties of carbon derived from seaweeds and their application in electrochemical supercapacitors.     

Protonic conducting organic/inorganic nanocomposites for polymer electrolyte membrane

Protonic conducting membrane can be used in many energy technological applications such as fuel cells, water electrolysis, hydrogen separation, sensors and other electrochemical devices. However, polymer electrolyte membrane usually lack thermal stability, resulting in narrow operational temperature windows. So, a new class of polymer membrane with high temperature stability and protonic conductivity is desired for many industrial applications. In this paper, new synthetic routes have been investigated for organic/inorganic nanocomposites hybrid polymer membranes of SiO₂/polymer (polyethylene oxides (PEO); polypropylene oxide (PPO); polytetramethylene oxide (PTMO)). Novel protonic conducting properties have also been investigated. The materials have been synthesized through sol–gel processes in flexible, ductile free-standing thin membrane form. The hybrid membrane has been found to be thermally stable up to 250°C and possess protonic conductivities of approximately 10⁻⁴ S/cm at temperature windows from room temperature to 160°C and relative humidity.     

Polyoxometallates as inorganic templates for electrocatalytic network films of ultra-thin conducting polymers and platinum nanoparticles

We develop a concept of fabrication of the multilayer network films on electrodes by exploring the ability of a Keggin-type polyoxometallate, phosphododecamolybdate (PMo(12)O(40)(3-)), to form stable anionic monolayers (templates) on carbon and metals including platinum. By repeated alternate treatments in the solution of PMo(12)O(40)(3-) (or in the colloidal suspension of polyoxometallate-protected Pt-nanoparticles) and in the solution of monomer (e.g. anilinium) cations, the amount of the material can be increased systematically (layer-by-layer) to form stable three-dimensional assemblies on electrode (e.g. glassy carbon) surfaces. In the resulting hybrid (organic-inorganic) films, the layers of negatively charged polyoxometallate, or polyoxometallate-protected (stabilized) Pt-nanoparticles, are linked or electrostatically attracted by ultra-thin layers of such positively charged conducting polymers as polyaniline (PANI), polypyrrole (PPy) or poly(3,4-ethylenedioxythiophene), PEDOT. Consequently, the attractive physicochemical properties of polymers and reactivity of polyoxometallate or noble metal particles are combined. The films are functionalized and show electrocatalytic properties towards reduction of nitrite, bromate, hydrogen peroxide or oxygen. They are of importance to the chemical and biochemical sensing as well as to the biochemical and medical applications.     

Hybrid Hydrogels of Porous Graphene and Nickel Hydroxide as Advanced Supercapacitor Materials

Graphene‐based hydrogels can be used as supercapacitor electrodes because of their excellent conductivity, their large surface area and their high compatibility with electrolytes. Nevertheless, the large aspect ratio of graphene sheets limits the kinetics of processes occurring in the electrode of supercapacitors. In this study, we have introduced in‐plane and out‐of‐plane pores into a graphene–nickel hydroxide (Ni(OH)₂) hybrid hydrogel, which facilitates charge and ion transport in the electrode. Due to its optimised chemistry and architecture, the hybrid electrode demonstrates excellent electrochemical properties with a combination of high charge storage capacitance, fast rate capability and stable cycling performance. Remarkably, the Ni(OH)₂ in the hybrid contributes a capacitance as high as 3138.5 F g^?1, which is comparable to its theoretical capacitance, suggesting that such structure facilitates effectively charge‐transfer reactions in electrodes. This work provides a facile pathway for tailoring the porosity of graphene‐based materials for improved performances. Moreover, this work has also furthered our understanding in the effect of pore and hydrogel structures on the electrochemical properties of materials.     

Rare-earth (Eu, Tb) hybrids through amide bridge: Chemically bonded self-assembly and photophysical properties

This work focuses on the construction of a series of chemically bonded rare-earth/inorganic/organic hybrid materials (TCH-Si-Ln, TCH-Si-Ln-Phen and TCH-Si-Ln-Bipy: Phen = 1,10-phenanthroline, Bipy = 2,2′-bipyridyl) using TCH-Si as an organic bridge molecule that can both coordinate to rare-earth ions (Eu³⁺ and Tb³⁺) and form an inorganic Si-O-Si network with tetraethoxysilane (TEOS) after cohydrolysis and copolycondensation through a sol-gel process. All of these hybrid materials exhibit homogeneous microstructures and morphologies, suggesting the occurrence of self-assembly of the inorganic network and organic chain. Measurements of the photoluminescent properties of these materials show that the ternary europium systems present stronger luminescent intensities than the binary hybrids, indicating that the introduction of the second ligands can sensitize the luminescence emission of the europium hybrid systems. However, in the terbium systems, this phenomenon was not observed.     

Biomass‐Derived Carbon Materials as Prospective Electrodes for High‐Energy Lithium‐ and Sodium‐Ion Capacitors

Biomass‐derived carbon materials have received special attention as efficient, low‐cost, active materials for charge‐storage devices, regardless of the power system, such as supercapacitors and rechargeable batteries. In this Minireview, we discuss the influence of biomass‐derived carbonaceous materials as positive or negative electrodes (or both) in high‐energy hybrid lithium‐ion configurations with an organic electrolyte. In such hybrid configurations, the electrochemical activity is completely different to conventional electrical double‐layer capacitors; that is, one of the electrodes undergoes a Faradaic reaction, whilst the counter electrode undergoes a non‐Faradaic reaction, to achieve high energy density. The use of a variety of biomass precursors with different properties, such as surface functionality, the presence of inherent heteroatoms, tailored meso‐/microporosity, high specific surface area, various degrees of crystallization, calcination temperature, and atmosphere, are described in detail. Sodium‐ion capacitors are also discussed, because they are an important alternative to lithium‐ion capacitors, owing to the low abundance and high cost of lithium. The electrochemical performance of carbonaceous electrodes in supercapacitors and rechargeable batteries are not discussed.