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[Display omitted] • CoFePBA with hierarchical hollow structure was prepared by anion exchange method. • The nanocomposite with hollow structure was prepared by heat-treatment of CoFePBA. • The synergistic effect among different components significantly enhanced OER activity. The microstructure of materials importantly affects their performance. As electrocatalyst materials, the performance of hollow-structure materials is usually better than that of solid materials because of the larger specific surface area, lower density, and more exposed active sites of hollow structure. Bimetallic catalysts usually exhibit better catalytic activity than monometallic catalysts because of the synergistic effects between different metal elements. Prussian blue and its analogues (PB/PBAs) are ideal precursors for preparing hollow-structure bimetallic catalysts due to their structure and composition characteristics. In this study, ZIF-67 hollow sphere (HS) was used as the template to prepare hierarchical hollow CoFePBA (H-SCP) through anion-exchange method. The oxygen evolution reaction (OER) catalytic performance of H-SCP was further improved by low-temperature heat treatment in N 2 atmosphere. The H-SCP-350 sample, which was obtained at a heat-treatment temperature of 350 ℃, was a bimetallic nanocomposite. Part of H-SCP was converted into metallic cobalt and cobalt-iron alloy during heat treatment. The synergistic effect among the different components effectively improved the electrocatalytic activity of the material. Therefore, H-SCP-350 showed the best OER catalytic performance among all samples. The overpotential was only 291mV at a current density of 10 mA cm−2 when tested in 1 M KOH electrolyte. [ABSTRACT FROM AUTHOR]

Abstract: Lithium‐ion batteries (LIBs) have been widely used in the field of portable electric devices because of their high energy density and long cycling life. To further improve the performance of LIBs, it is of great importance to develop new electrode materials. Various transition metal oxides (TMOs) have been extensively investigated as electrode materials for LIBs. According to the reaction mechanism, there are mainly two kinds of TMOs, one is based on conversion reaction and the other is based on intercalation/deintercalation reaction. Recently, hierarchically nanostructured TMOs have become a hot research area in the field of LIBs. Hierarchical architecture can provide numerous accessible electroactive sites for redox reactions, shorten the diffusion distance of Li‐ion during the reaction, and accommodate volume expansion during cycling. With rapid research progress in this field, a timely account of this advanced technology is highly necessary. Here, the research progress on the synthesis methods, morphological characteristics, and electrochemical performances of hierarchically nanostructured TMOs for LIBs is summarized and discussed. Some relevant prospects are also proposed. [ABSTRACT FROM AUTHOR]

A novel core–shell structured Co 11 (HPO 3 ) 8 (OH) 6 –Co 3 O 4 hybrid material was synthesized in a hydrothermal condition from the microporous Co 11 (HPO 3 ) 8 (OH) 6 microrod precursor. Due to the unique nano/microstructures, the assembled asymmetric all-solid-state supercapacitor (Co 11 (HPO 3 ) 8 (OH) 6 –Co 3 O 4 and graphene) showed a high gravimetric specific capacitance of 1.84 F cm −3 at 0.5 mA cm −2 and an excellent cycling stability with only 1.3% ca decay after 3000 cycling. The device delivered a maximum power density of 105 mW cm −3 at a current density of 1.5 mA cm −2 and possessed a maximum volumetric energy density of 0.48 mW h cm −3 at a current density of 0.5 mA cm −2 . The device also exhibited excellent flexibility. [ABSTRACT FROM AUTHOR]

1D Co 2.18 Ni 0.82 Si 2 O 5 (OH) 4 architectures assembled by ultrathin nanoflakes are synthesized for the first time by a hydrothermal method. We present a self-reacting template method to synthesize 1D Co 2.18 Ni 0.82 Si 2 O 5 (OH) 4 architectures using Ni(SO 4 ) 0.3 (OH) 1.4 nanobelts. A high-performance flexible asymmetric solid-state supercapacitor can be successfully fabricated based on the 1D Co 2.18 Ni 0.82 Si 2 O 5 (OH) 4 architectures and graphene nanosheets. Interestingly, the as-assembled 1D Co 2.18 Ni 0.82 Si 2 O 5 (OH) 4 architectures//Graphene nanosheets asymmetric solid-state supercapacitor can achieve a maximum energy density of 0.496 mWh cm −3 , which is higher than most of reported solid state supercapacitors. Additionally, the device shows high cycle stability for 10,000 cycles. These features make the 1D Co 2.18 Ni 0.82 Si 2 O 5 (OH) 4 architectures as one of the most promising candidates for high-performance energy storage devices. [ABSTRACT FROM AUTHOR]

Amorphous core–shell CoO@C and Mn 3 O 4 @C composites have been synthesized by documenting a simple glucose–ethanol-assisted approach and characterized by SEM, TEM, X-ray diffraction, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Electrochemical measurements are performed to examine the CoO@C composites, and the result shows that CoO@C structure has much higher capacitance, higher energy and power density and better cycling performance than that of C/CoO hybrids. This improvement can be attributed to the nature of core–shell structure, which promotes fast Faradaic charging and discharging reaction and also minimizes both the ionic and electronic transportation distances and therefore improves the resulting electrode kinetic performance. [ABSTRACT FROM AUTHOR]

Abstract: Magnetic CoFe2O4-functionalized graphene sheets (CoFe2O4–FGS) nanocomposites have been synthesized by hydrothermal treatment of inorganic salts and thermal exfoliated graphene sheets. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations show that cobalt ferrite nanoparticles with sizes of 10–40nm are well dispersed on graphene sheets. OH− was recognized as a tie to integrate the inorganic salts with the graphene sheets, which made reaction started and developed on the surface of graphene sheets and formed cobalt ferrite nanoparticles on graphene sheets. The adsorption kinetics investigation revealed that the adsorption of methyl orange from aqueous solution over the as-prepared CoFe2O4–FGS nanocomposites followed pseudo-second-order kinetic model and the adsorption capacity was examined as high as 71.54mgg−1. The combination of the superior adsorption of FGS and the magnetic properties of CoFe2O4 nanoparticles can be used as a powerful separation tool to deal with water pollution. [Copyright &y& Elsevier]

Hollow cobalt oxide is phosphated under an inert atmosphere to form a composite with interconnected porous structures. As an electrocatalyst for oxygen evolution reaction, the catalytic activity of this material is significantly better than Co 3 O 4. [Display omitted] • Amorphous porous CoP x -CoO y complex was constructed by low temperature phosphating. • The same structure was obtained when the method is applied to other oxides. • The structure can significantly increase the number of active sites required for OER. • The catalytic activity of the material for oxygen release reaction was better than that of Co 3 O 4. Interconnected porous structures and amorphous materials are widely used in the field of electrocatalysis owing to their rich catalytic active sites. Amorphous CoP x -CoO y composites with interconnected porous structures were constructed through low-temperature phosphating of cobalt oxides. Moreover, low-temperature phosphating of cobalt oxide and other metal oxides with different morphologies also produced the same porous structures, further proving the generality of this method. Interestingly, the prepared CoP x -CoO y catalyst has excellent electrocatalytic activity for oxygen evolution reactions in alkaline media. At a current density of 10 mA cm−2, an overpotential of 322 mV and a Tafel slope of 102 mV dec-1 are generated. In a 1 M KOH electrolyte, its electrochemical activity is significantly better than that of unphosphorylated Co 3 O 4. Under catalytic conditions, the excellent performance arises from the formation of the incorporation of phosphorus, amorphous phase and porous structures. The unique structure can provide a large number of active sites, significantly shortening the electron transfer pathway. This is the foundation of our research on the development of electrocatalysts with rich active sites. The synthesis of amorphous interconnected porous structures by introducing phosphorus will allow the application of high-efficiency catalysts in electrocatalysis and other important chemical reactions. [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) carbonaceous aerogel derived from biomass bacterial cellulose (BC) is introduced as a flexible framework for iron oxides in Li-ion batteries (LIBs). The 3D carbonized BC (CBC) with highly interconnected nanofibrous structure exhibits good electrical conductivity and mechanical stability. The amorphous Fe 2 O 3 is tightly coated on the nanofibers of CBC through a simple in situ thermal decomposition method. The obtained amorphous Fe 2 O 3 anode (denoted as A-Fe 2 O 3 @CBC) exhibits stable cycling performance and high rate capability when assembled into a half-cell, which is supposed to benefit from the well-dispersed Fe 2 O 3 nanoshells and the hierarchical pores in A-Fe 2 O 3 @CBC composite. The rational design of the nanostructure could improve the transportation of electrons/ions and effectively alleviate volume changes of Fe 2 O 3 during the electrochemical cycling. Meanwhile, the amorphous nature of the Fe 2 O 3 in anode provides an enhanced capacitive-like lithium storage and flexible structure of the active materials, resulting in much higher specific capacity and longer cycle life when compared with its crystalline counterpart. This work provides a promising approach to design and construct the flexible metal oxide anode materials based on 3D carbonaceous aerogel for high-performance LIBs. [ABSTRACT FROM AUTHOR]

Abstract: Ordered mesoporous carbons (OMCs) with controllable pore sizes in the range of 4–10nm are prepared by a template procedure using 2D hexagonal MSU-H and 3D cubic KIT-6 as hard templates and boric acid as the pore expanding agent. The electrochemical performances of the as-synthesized OMCs as electrode materials for electrochemical double layer capacitors (EDLCs) are characterized by cyclic voltammetry (CV), galvanostatic charge/discharge (GC) and electrochemical impedance spectroscopy (EIS) experiments in 30wt% KOH electrolyte. The influence of the pore size distributions of OMCs on the electrochemical capacitive performances is discussed. The prepared OMCs exhibit good capacitive behaviors with the specific capacitance values ranging from 143 to 205.3Fg−1 at a voltage scan rate of 5mVs−1 and 81 to 86% retained at a high scan rate of 100mVs−1. OMC-M-2 shows the highest specific surface capacitance value of 27.5μFcm−2 at 5mVs−1 with a peak pore size of 7.8nm and a Brunauer–Emmet–Teller (BET) surface area of 729.3m2 g−1. The analysis of two kinds of pore symmetries of OMCs with the same pore size of about 6.5nm shows that the 3D cubic OMC exhibited superior capacitive performance than the 2D hexagonal OMC. [Copyright &y& Elsevier]

Abstract: New ordered mesoporous carbons containing nickel oxide nanoparticles have been successfully synthesized by carbonization of sucrose in the presence of nickel acetate inside SBA-15 mesoporous silica template. The obtained samples were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption, and transmission electron microscopy (TEM). The NiO nanoparticles were embedded inside the mesoporous carbon framework due to the simultaneous pyrolysis of nickel acetate during carbonization. The electrochemical testing of the as-made nanocomposites showed a large specific capacitance of 230Fg−1 using 2M KOH as the electrolyte at room temperature. This is attributed to the nanometer-sized NiO formed inside mesoporous carbons and the high surface area of the mesopores in which the NiO nanoparticles are formed. Furthermore, the synthetic process is proposed as a simple and general method for the preparation of new functionalized mesoporous carbon materials, for various applications in catalysis, sensor or advanced electrode material. [Copyright &y& Elsevier]

Iron oxides are potential electrode materials for lithium-ion batteries because of their high theoretical capacities, low cost, rich resources, and their non-polluting properties. However, iron oxides demonstrate large volume expansion during the lithium intercalation process, resulting in the electrode material being crushed, which always results in poor cycle performance. In this paper, to solve the above problem, iron oxide/carbon nanocomposites with a hollow core–shell structure were designed. Firstly, an Fe2O3@polydopamine nanocomposite was prepared using an Fe2O3 nanocube and dopamine hydrochloride as precursors. Secondly, an Fe3O4@N-doped C composite was obtained by means of further carbonization treatment. Finally, Fe3O4@void@N-Doped C-x composites with core–shell structures with different void sizes were obtained by means of Fe3O4 etching. The effect of the etching time on the void size was studied. The electrochemical properties of the composites when used as lithium-ion battery materials were studied in more detail. The results showed that the sample that was obtained via etching for 5 h using 2 mol L−1 HCl solution at 30 °C demonstrated better electrochemical performance. The discharge capacity of the Fe3O4@void@N-Doped C-5 was able to reach up to 1222 mA g h−1 under 200 mA g−1 after 100 cycles. [ABSTRACT FROM AUTHOR]

Abstract: High-density Co3O4 nanowire arrays have been fabricated by a simple, solvent-free synthesis method inside the alumina pores. It has been found that the pore diameter played a key role in the formation of the Co3O4 nanowires. When the same reaction was performed in the narrow pores of the AAO template (<90nm), a mixture of nanoparticles and short nanorods were obtained. The nanorod consists of a lot of obvious grains, which form grain chains. However, continuous and uniform nanowires could be produced when the larger pores of AAO (>120nm) were applied. Selected-area electron diffraction (SAED) patterns revealed that the nanowires were single-crystalline. Electrochemical measurements by an electrochemical workstation indicate that the specific capacitance characteristics of the as-prepared Co3O4 nanowires are much higher than that of Co3O4 particles. [Copyright &y& Elsevier]

Abstract: Cuspate deltoid cobaltous oxide (CoO) crystallites with an average grain size of 3μm were obtained via developing the Co3O4 nanoplatelets under the KCl/NaCl flux atmosphere. The as-synthesized products were characterized by powder X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscope and selected area electron diffraction. The electrochemical properties of the products were investigated by an Electrochemical Workstation device at room temperature. It has been found that the final prepared cubic CoO crystallites are of uniform cuspate deltoid morphology. The results of electrochemical tests indicate that the CoO shows acceptable capacitive behavior with specific capacitance about 88F/g. [Copyright &y& Elsevier]