Polyrhodanine/NiFe2 O4 nanocomposite: A novel electrocatalyst for hydrazine oxidation reaction

This study reports a facile fabrication of magnetic polyrhodanine/nickel-ferrite (PR/NiFe₂O₄) nanoparticles as a novel electrocatalyst for oxidation of hydrazine. Several technique were utilized to indicate the properties of the synthesized nanocomposite including the X-ray diffractometry (XRD), scanning electron microscopy (SEM), and fourier transform infrared spectroscopy (FT-IR). The electrocatalytic activity of the PR/NiFe₂O₄ modified carbon paste electrode was examined for hydrazine oxidation in alkaline solution by cyclic voltametry (CV) and chronoamperometry (ChA) methods. According to the obtained results, the modified electrode showed a suitable catalytic activity for hydrazine electrooxidation at lower overpotential and a significant high response for hydrazine oxidation. Moreover, the findings indicate that the reaction follows a Cottrell in behaviour during CA experimentand the diffusion coefficient of hydrazine is determined to be 3.56 × 10^?9 cm² s^?1.     

Boosting the kinetics of oxygen and hydrogen evolution in alkaline water splitting using nickel ferrite /N-graphene nanocomposite as a bifunctional electrocatalyst

Design, synthesize and application of metal-oxide based bifunctional electrocatalysts with sustainability and efficient activity in water splitting is significant among the wide spread researches in energy applications. Herein, bifunctional electrocatalysts composed of NiFe₂O₄ dispersed on N-doped graphene has been prepared by in-situ polymerization and characterized for further bifunctional catalytic performances. The electrocatalyst exhibited bespoken performances as cathode in HER as well as anode in OER at alkaline electrolyte. The nanocomposite N-doped graphene/NiFe₂O₄ (NGNF) exhibited low overpotential of 184 mV in HER and 340 mV in OER for attaining the current density of 10 mA/cm² which is far better than their pristine counterparts. Similarly its Tafel slopes were found to be 82.9 mV/dec and 93.2 mV/dec for HER and OER. As an electrocatalyst NGNF outperformed pure nickel ferrite and graphene/NiFe₂O₄ (GNF) as bifunctional electrocatalyst with low overpotential and Tafel slopes. This indicates the impact of graphene and N-doping on graphene in the activity of pure NF. The graphene in the composite and the N-dopants provoked the catalytic activity and tuned the electron transfer and interaction with the electrolyte. Thus, herein we endow with strategies of preparing highly efficient bifunctional electrocatalysts by coupling spinel oxides and N-doped graphene for HER and OER.     

Visible light-driven hydrogen evolution by using mesoporous carbon nitride-metal ferrite (MFe2O4/mpg-CN; M: Mn,Fe, Co and Ni) nanocomposites as catalysts

Four different earth-abundant ferrite nanoparticles (MFe₂O₄, M: Mn, Fe, Co, Ni) with spinel structure were synthesized by using the surfactant-assisted high temperature thermal decomposition methods and then assembled on mesoporous graphitic carbon nitride (mpg-CN) to study their comparative catalysis for the photocatalytic hydrogen evolution reaction (HER) in the presence of Eosin-Y (EY) as a visible-light sensitizer. The yielded monodisperse ferrite nanoparticles and the MFe₂O₄/mpg-CN nanocomposites were characterized by using advanced analytical techniques including TEM, XPS, XRD, ICP-MS, and UV–Vis DRS. All the tested MFe₂O₄/mpg-CN nanocomposites provided the better catalytic performance than that of pristine mpg-CN in the photocatalytic HER and their photocatalytic HER rates are in the order of NiFe₂O₄/mpg-CN > CoFe₂O₄/mpg-CN > MnFe₂O₄/mpg-CN > Fe₃O₄/mpg-CN > mpg-CN. Among the tested MFe₂O₄/mpg-CN nanocomposites, NiFe₂O₄/mpg-CN nanocomposite provided the highest hydrogen generation of 14.56 mmol g⁻¹, which is 6.75 times greater than that of pristine mpg-CN and, using EY as a visible light sensitizer and triethanolamine (TEOA) as a sacrificial reagent. According to the optical properties and energy band positions of the nanocomposites, a plausible mechanism for the NiFe₂O₄/mpg-CN catalyzed HER is proposed to give insights on the highest activity of NiFe₂O₄/mpg-CN nanocomposites among others.     

Thermochemical two-step water splitting cycles by monoclinic ZrO2-supported NiFe2O4 and Fe3O4 powders and ceramic foam devices

A thermochemical two-step water splitting cycle is examined for NiFe₂O₄ and Fe₃O₄ supported on monoclinic ZrO₂ (NiFe₂O₄/m-ZrO₂ and Fe₃O₄/m-ZrO₂) in order to produce hydrogen from water at a high-temperature. The evolution of oxygen and hydrogen by m-ZrO₂-supported ferrite powders was studied, and reproducible and stoichiometric oxygen/hydrogen productions were demonstrated through a repeatable two-step reaction. Subsequently, a ceramic foam device coated with NiFe₂O₄/m-ZrO₂ powder was made and examined as a water splitting device by the direct irradiation of concentrated Xe-light in order to simulate solar radiation. The reaction mechanism of the two-step water splitting cycle is associated with the redox transition of ferrite/wustite on the surface of m-ZrO₂. A hydrogen/oxygen ratio for these redox powder systems exhibited good reproducibility of approximately two throughout the repeated cycles. The foam device loaded NiFe₂O₄/m-ZrO₂ powder was also successful with respect to hydrogen production through 10 repeated cycles. A ferrite conversion of 24-76% was obtained over an irradiation period of 30 min.     

Promoted effect of PANI on the preferential oxidation of CO in the presence of H2 over Au/TiO2 under visible light irradiation

A Polyaniline (PANI) assembled Au/TiO₂ catalyst (Au/TiO₂–PANI) was prepared by deposition–precipitation with the assistance of in-situ polymerization assistance, and was performed for oxidizing CO in H₂-rich stream under visible light irradiation. It is found that the as-prepared Au/TiO₂–PANI exhibited a higher activity of CO preferential oxidation (PROX) than the Au/TiO₂ without PANI decoration at room temperature under visible light irradiation. Based on the results of structure characterization, photo-absorbance, photo-electrochemical, electron paramagnetic resonance, and adsorbing CO and H₂ of Au/TiO₂–PANI, it is proposed that the photo-excited electrons of PANI could transfer to TiO₂ accompanied by suppressing the transfer of excited electrons induced by the localized surface plasmon resonance of Au nanoparticles to TiO₂, resulting in the increases in surface electron densities of both Au and TiO₂ sites. This will promote the activation of CO adsorbed at Au sites and the formation of O₂⁻ species at TiO₂ sites, and then the oxidation of CO. Meanwhile, the protonation of N atoms in PANI could cause a spillover of the dissociative H at Au sites into PANI, resulting in the suppression of H₂ oxidation.     

Synthesis of magnetic Ag3PO4/Ag/NiFe2O4 composites towards super photocatalysis and magnetic separation

The synthesis of Ag₃PO₄/Ag was performed through in-situ deposition and photo-reduction processes with magnetic NiFe₂O₄ nanofibers towards enhanced photocatalysis performance and stability. NiFe₂O₄ inhibit the photoreduction of Ag₃PO₄ into Ag and resulted in high stability. The photocatalytic activity of Ag₃PO₄/Ag/NiFe₂O₄ samples was studied by methylene blue degrading under visible light irradiation. The Ag₃PO₄/Ag/NiFe₂O₄ photocatalyst with NiFe₂O₄ loading of 3% revealed good photocatalytic performance, high stability and quick degradation after 5 cycles. Photoluminescence spectra and photocurrent tests demonstrated that the formation of hetero-junction facilitated the separation of photo-generated carriers. The trapping experiments confirmed that h⁺ and ?OH were active species during the degradation process.     

Growth of polyaniline on rGO-Co3S4 nanocomposite for high-performance supercapacitor energy storage

Recently, since the supercapacitors have drawn considerable attention, a vast study have been triggered in order to develop efficient electrodes for responding to the increasing demand of supercapacitors. In this report, a possible approach have been used to prepare a ternary nanocomposite, polyaniline/reduced graphene oxide-cobalt sulfide (PANI/rGO-Co₃S₄). At first, a simple and inexpensive hydrothermal route has been used for the preparation of cobalt sulfide (Co₃S₄) on the surface of graphene oxide sheets (rGO-Co₃S₄). Then, the polyaniline nanorods have been flourished on the surface of rGO-Co₃S₄ sheets via in situ chemical polymerization of aniline which was synergistically adjoined to the graphene surface. Polyaniline has uniformly covered the surface of the rGO-Co₃S₄ due to the rational combination of two components. Combining of PANI with rGO-Co₃S₄ electrode material amplify its electrochemical efficiency in terms of a high specific capacitance of 767 F g^?1 at 1 A g^?1 and 81.7% of specific capacitance maintenance after 5000 cycles due to the creation of synergistic effect. Therefore, the ternary nanocomposite of PANI/rGO-Co₃S₄ provides a new promising pathway for the expanding of high-performance electrode materials for supercapacitors.     

Construction of dual Z-scheme NiO/NiFe2O4/Fe2O3 photocatalyst via incomplete solid state chemical combustion reactions for organic pollutant degradation with simultaneous hydrogen production

A dual Z-scheme NiO/NiFe₂O₄/Fe₂O₃ photocatalyst is prepared via incomplete solid state chemical combustion reaction of Ni(OH)₂ and Fe(OH)₃. The formed perfect interfaces between NiO and NiFe₂O₄ and between NiFe₂O₄ and Fe₂O₃ facilitate the transfers of photo-induced electrons. The photocatalytic degradation of methylene blue and simultaneous production of hydrogen was performed to evaluate the activity of the prepared samples. The dual Z-scheme NiO/NiFe₂O₄/Fe₂O₃ (600–2) photocatalyst obtained by heat treatment of Ni(OH)₂ and Fe(OH)₃ at 600 °C for 2.0 h shows an excellent photocatalytic performance. Additionally, the influences of simulated sunlight irradiation time and methylene blue concentration on the photocatalytic reactions are investigated. Besides, the reusability of sample is assessed via four cycle experiments. Further, a possible mechanism on the photocatalytic reaction is proposed. Maybe, this work would provide an ingenious idea for the construction of dual Z-scheme photocatalyst and the exploration for photocatalytic degradation of organic pollutants with simultaneous hydrogen production.     

Photocatalytic hydrogen production from aqueous methanol solution with CuO/Al2O3/TiO2 nanocomposite

The photocatalytic hydrogen production from aqueous methanol solution was investigated with ZnO/TiO₂, SnO/TiO₂, CuO/TiO₂, Al₂O₃/TiO₂ and CuO/Al₂O₃/TiO₂ nanocomposites. A mechanical mixing method, followed by the solid-state reaction at elevated temperature, was used for the preparation of nanocomposite photocatalyst. Among these nanocomposite photocatalysts, the maximal photocatalytic hydrogen production was observed with CuO/Al₂O₃/TiO₂ nanocomposites. A variety of components of CuO/Al₂O₃/TiO₂ photocatalysts were tested for the enhancement of H₂ formation. The optimal component was 0.2 wt% CuO/0.3 wt% Al₂O₃/TiO₂. The activity exhibited approximately tenfold enhancement at the optimum loading, compared with that with pure P-25 TiO₂. Nano-sized TiO₂ photocatalytic hydrogen technology has great potential for low-cost, environmentally friendly solar-hydrogen production to support the future hydrogen economy.     

Fe2O3/spinel NiFe2O4 heterojunctions in-situ wrapped by one-dimensional porous carbon nanofibers for boosting oxygen evolution/reduction reactions

One-dimensional (1D) nanofiber structure of electrocatalyst has attracted increasing attention in oxygen evolution/reduction reactions (OER/ORR) owing to its unique structural properties. Here, MIL-53(Fe) and Ni(NO₃)₂·6H₂O are incorporated into the electrospun carbon nanofibers (CNFs) to prepare the nickel-iron spinel-based catalysts (Fe₂O₃/NiFe₂O₄@CNFs) with 1D and porous structure. The marked Fe₂O₃/NiFe₂O₄@CNFs-2 catalyst has a tube diameter of approximately 300 nm, a high surface area of 282.4 m² g^?1 and a hydrophilic surface (contact angle of 16.5°), which obtains a promising bifunctional activity with ΔE = 0.74 V (E_1/2 = 0.84 V (ORR) and E_j10 = 1.58 V (OER)) in alkaline media. Fe₂O₃/NiFe₂O₄@CNFs-2 has a higher catalytic stability (93.35%) than Pt/C (89.36%) for 30,000 s tests via an efficient 4e^? ORR pathway. For OER, Fe₂O₃/NiFe₂O₄@CNFs-2 obtains a low overpotential of 350 mV and a high Faraday efficiency of 92.7%. NiFe₂O₄ (Ni²⁺ in tetrahedral position) relies on its variable valence states (NiOOH and/or FeOOH) to obtain good catalytic activity and stability for OER, while CNFs wrap/protect the active components (Fe–N and graphic N) in the carbon skeleton to effectively improve the charge transfer (conductivity), activity and stability for ORR. Porous 1D nanofiber structure provides abundant smooth pathways for mass transfer. It indicates that the bimetallic active substances can promote bifunctional activity by synergistically changing the oxide/spinel interface structure.     

Facile reduction of nitrophenols: Comparative catalytic efficiency of MFe2O4 (M = Ni,Cu, Zn) nano ferrites

Nano ferrites of the formula MFe₂O₄ (M = Ni, Cu, Zn), synthesized using sol–gel technique, were employed to catalyze the reductive transformation of nitrophenols to aminophenols. The catalytic reduction was carried out in the excess of NaBH₄ as reducing agent in aqueous medium at room temperature. CuFe₂O₄ and NiFe₂O₄ were found to be active for the reduction of nitrophenols with significant difference in their activities whereas ZnFe₂O₄ was found to be inactive. The kinetics of the reduction of nitrophenols to aminophenols was also investigated. The reaction followed pseudo first order kinetics. The first order rate constant values for 30 mol% of CuFe₂O₄ and NiFe₂O₄ for the reduction of 2-nitrophenol were observed to be 3.68 min⁻¹ and 0.33 min⁻¹ respectively. The rates of reduction for the three isomers of nitrophenol were also studied and were observed to follow the order – 2-nitrophenol > 4-nitrophenol > 3-nitrophenol. The selective formation of aminophenol was confirmed using LC-MS, ¹H NMR and FT-IR spectroscopic techniques.     

Construction of ternary hybrid layered reduced graphene oxide supported g-C3N4-TiO2 nanocomposite and its photocatalytic hydrogen production activity

Reduced graphene oxide (rGO) supported g-C₃N₄-TiO₂ ternary hybrid layered photocatalyst was prepared via ultrasound assisted simple wet impregnation method with different mass ratios of g-C₃N₄ to TiO₂. The synthesized composite was investigated by various characterization techniques, such as XRD, FTIR, Raman Spectra, FE-SEM, HR-TEM, UV vis DRS Spectra, XPS Spectra and PL Spectra. The optical band gap of g-C₃N₄-TiO₂/rGO nanocomposite was found to be red shifted to 2.56 eV from 2.70 eV for bare g-C₃N₄. It was found that g-C₃N₄ and TiO₂ in a mass ratio of 70:30 in the g-C₃N₄-TiO₂/rGO nanocomposite, exhibits the highest hydrogen production activity of 23,143 μmol g^?1h^?1 through photocatalytic water splitting. The observed hydrogen production rate from glycerol-water mixture using g-C₃N₄-TiO₂/rGO was found to be 78 and 2.5 times higher than g-C₃N₄ (296 μmol g^?1 h^?1) and TiO₂ (11,954 μmol g^?1 h^?1), respectively. A direct contact between TiO₂ and rGO in the g-C₃N₄-TiO₂/rGO nanocomposite produces an additional 10,500 μmol g^?1h^?1 of hydrogen in 4 h of photocatalytic reaction than the direct contact between g-C₃N₄ and rGO. The enhanced photocatalytic hydrogen production activity of the resultant nanocomposite can be ascribed to the increased visible light absorption and an effective separation of photogenerated electron-hole pairs at the interface of g-C₃N₄-TiO₂/rGO nanocomposite. The effective separation and transportation of photogenerated charge carriers in the presence of rGO sheet was further confirmed by a significant quenching of photoluminescence intensity of the g-C₃N₄-TiO₂/rGO nanocomposite. The photocatalytic hydrogen production rate reported in this work is significantly higher than the previously reported work on g-C₃N₄ and TiO₂ based photocatalysts.     

Electrochemically synthesized polypyrrole/MWCNTs-Al2O3 ternary nanocomposites supported Pt nanoparticles toward methanol oxidation

As known, a good support enhances the activity and durability of any catalyst. In the current study, polypyrrole (PPY)/nanocomposite (MWCNTs and Al₂O₃) films were fabricated by electrochemical polymerization of pyrrole solution with a certain amount of nanoparticles on titanium substrates and were used as new support materials for Pt catalyst. The modified electrodes were characterized by Fourier transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDX) techniques. High catalytic activity and long-time stability toward methanol oxidation of Pt/PPY–MWNTs-αAl₂O₃ catalyst have also been verified by cyclic voltammetry results and chronoamperometric response measurements. This catalyst exhibits a vehemently high current density (345.03 mA cm^?2) and low peak potential (0.74 v) for methanol oxidation. Other electrochemical measurements (electrochemical impedance spectroscopy (EIS), CO stripping voltammetry and Tafel test) clearly confirmed that Pt/PPY–MWNTs-αAl₂O₃/Ti electrode has a better performance toward methanol oxidation compared to the other electrodes and that can be used as a promising electrode material for application in direct methanol fuel cells (DMFCs).     

In situ fabrication of CDs/g-C3N4 hybrids with enhanced interface connection via calcination of the precursors for photocatalytic H2 evolution

Novel carbon dots (CDs)/graphitic carbon nitride (g-C₃N₄) hybrids were fabricated via an in situ thermal polymerization of the precursors, urea and glucose. This heterojunction catalyst exhibited enhanced photocatalytic H₂ evolution activity under visible-light (λ > 420). A sample of CDs/g-C₃N₄ hybrids, CN/G0.5, which was prepared from 0.5 mg of glucose in 6.0 g of urea (8.3 × 10^?3 wt% glucose), exhibited the best photocatalytic performance for hydrogen production from water under visible light irradiation, which is about 4.55 times of that of the bulk g-C₃N₄ (BCN). The improvement of photocatalytic activity was mainly attributed to the construction of built-in electric field at the interface of CDs and g-C₃N₄, which could improve the separation of photogenerated electron-hole pair. Moreover, the tight connection of CDs with g-C₃N₄ would serve as a well electron transport channel, which could promote the photocatalytic H₂ evolution ability.     

CuCr2O4/TiO2 heterojunction for photocatalytic H2 evolution under simulated sunlight irradiation

CuCr₂O₄/TiO₂ heterojunction has been successfully synthesized via a facile citric acid (CA)-assisted sol-gel method. Techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-vis diffuse reflectance spectrum (UV-vis DRS) have been employed to characterize the as-synthesized nanocomposites. Furthermore, photocatalytic activities of the as-obtained nanocomposites have been evaluated based on the H₂ evolution from oxalic acid solution under simulated sunlight irradiation. Factors such as CuCr₂O₄ to TiO₂ molar ratio in the composites, calcination temperature, photocatalyst mass concentration, and initial oxalic acid concentration affecting the photocatalytic hydrogen producing have been studied in detail. The results showed that the nanocomposite of CuCr₂O₄/TiO₂ is more efficient than their single part of CuCr₂O₄ or TiO₂ in producing hydrogen. The optimized composition of the nanocomposites has been found to be CuCr₂O₄·0.7TiO₂. And the optimized calcination temperature and photocatalyst mass concentration are 500 °C and 0.8 g l⁻¹, respectively. The influence of initial oxalic acid concentration is consistent with the Langmuir model.     

Facile construction of self-assembled Cu@polyaniline nanocomposite as an efficient noble-metal free cocatalyst for boosting photocatalytic hydrogen production

Photocatalytic Hydrogen production via water splitting is considered a sustainable ecofriendly pathway to replenish the current and future energy demands. In this study, the self-assembly synthesis of Cu nanospheres (～8 nm) surrounded by a thin conductive layer of polyaniline (Cu@PANI) was rationally engineered via in?situ polymerization. Afterward, it was successfully deposited onto the TiO₂ surface to improve the photocatalytic activities for hydrogen production. The optimal Cu@PANI/TiO₂ ternary photocatalyst produced a substantial hydrogen generation rate (HGR) of 17.7 mmol h^?1 g^?1, 207-fold higher than that of bare TiO₂. The performance was considerably improved compared with (Cu–TiO₂)/PANI and (PANI-TiO₂)/Cu composites prepared by changing the deposition sequence of Cu and PANI. Such an improved activity was because of multiple transferring paths of photogenerated electrons in the composite. Interestingly, the as-prepared ternary photocatalyst exhibited superior hydrogen evolution compared with the binary hybrids (Cu/TiO₂ and PANI/TiO₂). The exceptional performance of Cu@PANI/TiO₂ could be understood considering the distinctive electrical conductivity of PANI and heterojunction formed between PANI and TiO₂, as well as the merits of the Schottky junction constructed between Cu and PANI. These superior features could efficiently suppress the recombination rate of the photogenerated electron–hole pairs and maximize the photocatalytic activity. This study provides new insights for understanding the effect of electron transfer pathways on photocatalytic activities.     

Photocatalytic hydrogen evolution of nanoporous CoFe2O4 and NiFe2O4 for water splitting

The spinels CoFe₂O₄ and NiFe₂O₄ of nanoporous photocatalysts were prepared by dealloying and calcination. The photocatalytic performance for the hydrogen generation rate via water splitting was measured. The results revealed that CoFe₂O₄ exhibits a sheet-like nanoporous structure and that abundant mesopores are distributed in the nanosheets. NiFe₂O₄ shows a typical pore-ligament structure. The measurements show that hydrogen generation is exhibited by both oxides because the bandgap of CoFe₂O₄ and NiFe₂O₄ is higher than the water oxidization potential. The hydrogen generation rate is approximately 0.088 mmol h^?1g^?1 for CoFe₂O₄ and 0.026 mmol h^?1g^?1 for NiFe₂O₄ when the TEOA (10 vol%) sacrificial agent is adopted. This performance is significantly higher than that of methanol as the scavenger because TEOA increases the pH value of the solution, changes the negative shift in the conduction band energy level and improves the electron transport efficiency. The higher performance of CoFe₂O₄ is attributed to its larger specific surface area, ample unimpeded penetration diffusion paths and higher electron transfer rate.     

Preparation and photocatalytic properties of HLaNb2O7/(Pt,TiO2) perovskite intercalated nanomaterial

A novel perovskite intercalated nanomaterial HLaNb₂O₇/(Pt, TiO₂) is fabricated by successive intercalated reaction of HLaNb₂O₇ with [Pt(NH₃)₄]Cl₂ aqueous solution, n-C₆H₁₃NH₂/C₂H₅OH organic solution and acidic TiO₂ colloid solution, followed by ultraviolet light irradiation. The gallery height and the band gap energy of HLaNb₂O₇/(Pt, TiO₂) is less than 0.6 nm and 3.14 eV, respectively. The photocatalytic activity of HLaNb₂O₇/TiO₂ is superior to that of unsupported TiO₂ and is enhanced by the co-incorporation of Pt. The photocatalytic hydrogen evolution based on HLaNb₂O₇/(Pt, TiO₂) is 240 cm³ h⁻¹ g⁻¹ using methanol as a sacrificial agent under irradiation with wavelength more than 290 nm from a 100-W mercury lamp. High photocatalytic activity of HLaNb₂O₇/(Pt, TiO₂) may be due to the host with rare earth La element and perovskite structure, the quantum size effect of intercalated semiconductor and the coupling effect between host and guest.     

Facile synthesis of hierarchically structured Fe3O4/carbon micro-flowers and their application to lithium-ion battery anodes

A flower-like Fe₃O₄/carbon nanocomposite with nano/micro hierarchical structure is prepared by controlled thermal decomposition of the iron alkoxide precursor, which is obtained via an ethylene glycol-mediated solvothermal reaction of FeCl₃ and hexamethylenetetramine (HMT) in the absence of any surfactant. The nanocomposite is characterized by the assembly of porous nanoflakes consisting of Fe₃O₄ nanoparticles and amorphous carbon that is in situ generated from the organic components of alkoxide precursor. When used as the anode materials for the lithium-ion batteries, the resultant nanocomposite shows high capacity and good cycle stability (1030 m Ah g⁻¹ at a current density of 0.2 C up to 150 cycles), as well as enhanced rate capability. The excellent electrochemical performance can be attributed to the high structural stability and high rate of ionic/electronic conduction arising from the synergetic effect of the unique nano/micro hierarchical structure and conductive carbon coating.