Single-atom co sites confined in layered double hydroxide for selective generation of surface-bound radicals via peroxymonosulfate activation

Selective production of specific radical species with prolonged lifetime is challenging in advanced oxidation process. Herein, we constructed single-atom Co (SA-Co) catalytic sites confined in layered double hydroxide (LDH) for selectively and sustainably generate radical species via peroxymonosulfate (PMS) activation. The negatively charged PMS was stabilized by the positively charged LDH and simultaneously activated by the nanoconfined Co single-atom sites, resulting in oriented-production of surface-bonded •OH and SO₄^•− radicals with long-term efficiency (up to 48 h), suppressed PMS decomposition and radical self-quenching. Ion competition experiments and in-situ spectroscopic studies were applied to monitor the PMS activation processes. The SA-Co-LDH/PMS system outperforms the benchmark homogeneous (Co²⁺/PMS) and heterogeneous (Co₃O₄/PMS) catalytic systems for the degradation of emerging organic contaminants (EOCs) with the lowest Co consumption and highest catalytic efficiency.     

The role of crystalline Nb2O5 nanoparticles for enhanced dye adsorption and photodegradation

Niobium pentoxide (Nb₂O₅) nanoparticles have attracted attention in recent years due to their enhanced adsorption and photocatalysis properties against emerging contaminants. The photocatalytic properties of niobium pentoxide are directly related to defects and non-stoichiometric phases in its structure. This work presents the synthesis of Nb₂O₅ nanoparticles using the Pechini method and precursor decomposition techniques. X-ray diffraction (XRD) showed the presence of niobium pentoxide crystallized in TT, T, H, and the non-stoichiometric Nb₁₂O₂₉ phases. The samples calcined at 500 °C showed a specific surface area (SSA) between 55 and 65 m² g^?1, acting as a good adsorbent and photocatalyst to degrade crystal violet (CV). The contaminant adsorption process was studied and optimized using zeta-potential analysis, showing a negatively charged surface at pH > 2, with optimal adsorption at pH = 10. The adsorption study showed the best fit for the adsorption isotherm proposed by Liu and also the possibility of reusing Nb₂O₅. The photodegradation of crystal violet dye using Nb₂O₅ as catalyst showed synergetic properties, in which samples with higher SSA and crystallization in the TT-phase decolored the solution in 2 h 30 min. However, the mixture of H–Nb₂O₅ and Nb₁₂O₂₉ also showed good adsorption properties and decolored the CV pollutant in 2 h 30 min, demonstrating that adsorption and photodegradation mechanisms strongly depend on the crystalline phase of the niobium pentoxide.     

Two inorganic–organic hybrid compounds based on [Ni2(V3O9)2]2− cluster and {Co2V2} cage subunits

Two novel inorganic-organic hybrid compounds (Ni₃(Hfcz)₄(V₃O₉)₂? 2H₂O) (1) and Co₅(H₂O)₄(fcz)₂(V₄O₁₂)₂ (2) have been successfully constructed, based on [Ni₂(V₃O₉)₂]^2? “bow tie” clusters and {Co₂V₂} pure inorganic cages. Structural analysis reveals that the clusters and cages are expanded to a 2D network and 3D framework via Ni^II and Co^II, respectively. In addition, we investigated the optical band gaps of the two compounds: 2.92 eV and 2.23 eV.     

Protic Ionic Liquid Assisted Synthesis and Characterization of Ferromagnetic Cobalt Oxide Nanocatalyst

Cobalt oxide (Co₃O₄) nanocatalyst was synthesized by sol-gel method using the protic ionic liquid namely 1-butylimidazolium glycolate as solvent and stabilizer. The obtained Co₃O₄ nanocatalyst was characterized by powder X-ray diffraction (XRD), Fourier transform infrared, High resolution scanning electron microscopy (HR-SEM), Energy dispersive X-ray (EDX), High resolution transmission electron microscopy (HR-TEM), Selected area electron diffraction, UV–Visible diffuse reflectance spectroscopy, Photoluminescence spectroscopy, Brunauer–Emmett–Teller surface area and Vibrating sample magnetometer (VSM). Powder XRD results showed the well-crystalline cubic structure of synthesized Co₃O₄ with size of 19.29 nm. Also, the sphere-like morphology of Co₃O₄ nanocatalyst was confirmed by HR-SEM and HR-TEM images. Furthermore, the synthesized Co₃O₄ nanocatalyst possessed optical band gap values of 1.75 and 2.46 eV and hence acted as a semiconducting material. In addition, the presence of small hysteresis loop in Magnetic measurement (VSM) confirmed the ferromagnetic nature of Co₃O₄ nanoparticles. Moreover, the synthesized Co₃O₄ nanocatalyst found to be used in photo-catalytic degradation of methylene blue and exhibited 94.61% efficiency.     

Template-free synthesis of novel Co3O4 micro-bundles assembled with flakes for high-performance hybrid supercapacitors

In this paper, a novel Co₃O₄ micro-bundles structure (Co₃O₄ MBs) was obtained at 120 °C after a hydrothermal reaction for 24 h and followed by an annealing treatment at 300 °C in air. The unique Co₃O₄ MBs are constructed by many adjacent flakes with 0.4 μm in thickness, and exhibit a large surface area of 81.2 m² g^?1 and a mean pore diameter of 6.14 nm, which may facilitate a sufficient contact with electrolyte and then shorten the diffusion pathway of ions. A remarkable electrochemical behavior including specific capacity of 282.3 C g^?1 at 1 A g^?1 and 205.9 C g^?1 at 10 A g^?1, and an excellent cycling performance with 74.6% capacity retention after 4000 charge-discharge process at 5 A g^?1 are achieved when the test of Co₃O₄ MBs-modified electrode is performed using three-electrode configuration. Additionally, a hybrid supercapacitor (HSC) was fabricated with the obtained Co₃O₄ MBs as positive electrode and commercial activated carbon (AC) as negative electrode. The HSC exhibits a specific capacity of 144.1 C g^?1 at 1 A g^?1 and 126.4% capacity retention after 5000 cycles at 5 A g^?1. An energy density of 38.5 W h kg^?1 can be obtained at a power density of 962.0 W kg^?1, and 29.5 W h kg^?1 is still retained at 8532.5 W kg^?1. The simple synthetic strategy can be applicable to the synthesis of other transition metal oxides with superior electrochemical performance.     

Sulfate radical-based ferrous–peroxymonosulfate oxidative system for PCBs degradation in aqueous and sediment systems

Polychlorinated biphenyls (PCBs) in the environment pose long-term risk to public health because of their persistent and toxic nature. This study investigates the degradation of PCBs using sulfate radical-based advanced oxidation processes (SR-AOPs). These processes are based on the generation of sulfate radicals through iron (Fe(II), Fe(III)) mediated activation of peroxymonosulfate (KHSO₅, PMS) or persulfate (Na₂S₂O₈, PS). This study is the first instance for coupling of Fe(II)/Fe(III) with PMS for PCB degradation in aqueous and sediment systems. The high oxidation efficiencies of the free radicals (SO₄⁻), in combination with the slow rate of consumption of the oxidants, make these processes very effective for the degradation of recalcitrant organic compounds. The effectiveness of the process was evaluated based on the degradation of a model polychlorinated biphenyl, 2-chlorobiphenyl and total organic carbon (TOC) removal. The kinetics of 2-chlorobiphenyl degradation along with the effect of oxidant and catalyst concentrations on the degradation efficiency was studied. Near complete removal of 2-chlorobiphenyl was observed when Fe(II) was used with PMS or PS. Fe(II) acts as a sulfate radical scavenger at higher concentrations indicating that there is an optimum concentration of Fe(II) that leads to most effective degradation of the target contaminant. A chelating agent, sodium citrate, was used to control the quantity of iron in the solution for activation of the oxidant. For the first time, we studied the feasibility of the activation of PMS using iron citrate complexes for PCB degradation. In the presence of sodium citrate, increase in degradation efficiency was observed up to a metal:ligand ratio of 1:2, after which the increase in citrate concentration led to a decrease in removal efficiency. Fe(II)/PMS systems were found to be very effective in degrading PCB in a sediment-slurry system with more than 90% PCB removal being observed within 24 h.     

Effect of calcination temperature on structural,morphological and electrochemical properties of Sn doped Co3O4 nanorods

Tremendous attention has been devoted for the development of highly efficient and stable electrode materials for supercapacitor applications. In this study, Sn-doped Co₃O₄ nanorods were prepared via solvothermal process using PVP and oxalic acid as surfactants. The phase, morphology and composition of Sn-doped Co₃O₄ nanorods were examined by XRD and SEM/EDX techniques. The electrochemical properties were studied via cyclic voltammetry (CV), galvanostatic charging-discharging (GCD), electrochemical impedance spectroscopy (EIS) measurements. The CV results show that electrode based on 5 at. % Sn-doped Co₃O₄ (5Sn-doped Co₃O₄) nanorods delivered the highest specific capacitance (842.44 F/g) at 5 mV/s than that of the electrode based on pure Co₃O₄ (729.39 F/g). In order to further tune the performance of this electrode, the structure, morphology and electrochemical behavior of 5Sn-doped Co₃O₄ sample were optimized via variety of calcination temperatures ranging from 250 to 400 °C. Notably, the 5Sn-doped Co₃O₄ sample calcined at 350 °C exhibited higher electrochemical performance (specific capacitance ~913.10 F/g) than other samples calcined at low or high calcination temperatures. The CV curves of 5Sn-doped Co₃O₄/T-350 °C at scan rates of 5–35 mV/s also showed pseudocapacitor behavior and good electrochemical reversibility. Moreover, the prepared novel electrode material has also displayed good rate capability (71.77%) at current density of 1–10 A/g and long-term stability of 92.23% after 3000 cycles. These excellent electrochemical characteristics of 5Sn–Co₃O₄/T-350 °C nanorods verified that it will be highly suitable electrode material for supercapacitor applications.     

Fabrication and characterization of MOCVD (In1-xAlx)2O3 (0.1≤x≤0.6) ternary films

A series of (In_1-xAl_x)₂O₃ (0.1 ≤ x ≤ 0.6) films with tunable bandgap were grown on MgO (100) substrates by MOCVD. The influences of chemical compositions and growth temperatures on the film properties were studied systematically. XRD analyses indicated that the film quality degraded from crystalline to amorphous structure as Al concentration (x) increased. The (In_1-xAl_x)₂O₃ films prepared at 700 °C exhibited better film crystallinity than those of the ones grown at 600 °C. The films prepared at 700 °C with x = 0.1–0.3 showed an epitaxial In₂O₃ <111> orientation with the corresponding growth relationship of In₂O₃ (111)∥MgO (100). The film with x = 0.2 exhibited the best crystallinity and the largest grain size of 25.9 nm. The Hall mobilities and resistivities of the films were influenced evidently by Al concentrations. The Hall mobility showed a monotonous decrease from 12 to 1.1 cm²V^?1s^?1 as x increased from 0.1 to 0.6. The lowest resistivity of 9.2 × 10^?3 Ω cm was acquired for the film with x = 0.2. The average transmittances in the visible region for all the films were beyond 83%. The bandgap of the (In_1-xAl_x)₂O₃ films can be regulated in the range of 3.85–4.88 eV by changing Al concentrations from 0.1 to 0.6.     

π‐Complexation Studied by Fluorescence Technique: Application in Desulfurization of Petroleum Product using Magnetic π‐Complexation Sorbents

Abstract

Magnetic π‐complexation sorbents were studied for petroleum product desulfurization by fluorescent technique. The ability of metal cation to form π‐complexation decreases in the order following: Cu⁺>Ni²⁺>Co²⁺>Al³⁺. The order is consistent with that of desulfurization performance of their corresponding magnetic sorbents (γ‐Al₂O₃‐Cu(I)>γ‐Al₂O₃‐Ni(II)>γ‐Al₂O₃‐Co(II)>γ‐Al₂O₃). Both π‐complexation strength and desulfurization performance of the sorbents increase with temperature. The adsorptive performances of magnetic γ‐Al₂O₃‐Cu(I) sorbent to different compounds have the following orders: DBT>fluorene, and pyrene>naphthalene>benzene, respectively. In this study, dibenzothiophene (DBT) was used as a model sulphur‐containing compound for desulfurization. The maximal adsorption amount of magnetic γ‐Al₂O₃‐Cu(I), was 0.362 mmol DBT g^?1.     

Effect of dopant on ferroelectric,dielectric and photocatalytic properties of Co–La-doped dysprosium chromite prepared via microemulsion route

In the current study, pristine and a series of La and Co-doped dysprosium chromite (Dy_1-yLa_yCr_1-xCo_xO₃) nanoparticles have been fabricated via a facile microemulsion technique. The influence of doping was evaluated based on structural, ferroelectric, dielectric, and photocatalytic properties. The prepared nanoparticles were characterized by XRD, SEM, Raman, and UV–Vis techniques. XRD patterns confirm the synthesis of a monophase orthorhombic structure with space group Pbnm with an average crystalline size in the 18–37 nm range. The saturation polarization (Ps), remanence (Pr), and coercivity (Hc) were determined using a hysteresis loop, and it was observed that by increasing the concentration of dopants, the value of Ps and Pr were improved. According to the PL spectra, highly substituted materials had a low recombination rate and higher charge separation (e^? - h⁺), which was ultimately accountable for higher photocatalytic activity. The dielectric loss decreases with frequency and dopant concentration. The photocatalytic activity of Dy_1-yLa_yCr_1-xCo_xO₃ was investigated against Crystal Violet (CV) dye under sunlight irradiation. The Dy_1-yLa_yCr_1-xCo_xO₃ furnished a 70% dye degradation in 90 min, which is attributed to the tunned bandgap and efficient electron-hole pair separation and the photocatalytic activity under visible light making Dy_1-yLa_yCr_1-xCo_xO₃ a promising photocatalyst for dye removal from wastewater.     

Preparation,characterisation and catalytic evaluation of MgF2 supported V2O5 catalysts for ammoxidation of 3-picoline

Non-conventional MgF₂ supported V₂O₅ catalysts with different vanadia contents (2–15 wt.%) were prepared by impregnation (using NH₄VO₃), characterised and catalytically evaluated for selective ammoxidation of 3-picoline to nicotinonitrile. Oxygen and ammonia chemisorption uptakes increased continuously from 60 to over 600 μmol g^?1 and 275 to >750 μmol g^?1, respectively, with rise in V₂O₅ proportion indicating that the redox as well as acidic sites are increasing with increase in V₂O₅ content. Thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) analysis revealed endothermic as well as exothermic thermal effects mainly due to liberation of water and ammonia, and also due to structural changes. XRD patterns showed the formation of crystalline V₂O₅ in the fresh solids having 8 wt.% V₂O₅ and above and NH₄VO₃ phase in the spent samples. The conversion of 3-picoline is observed to increase continuously with increase in V₂O₅ loading. However, the selectivity of nicotinonitrile is found to be independent on conversion of 3-picoline. The catalyst with the highest V₂O₅ loading (15.7 wt.%) displayed the best activity (X > 90%) and selectivity (S > 95%) compared to all other catalysts of this series. The 3-picoline conversion of 10% at 548 K is increased to almost 100% with rise in temperature to 663 K. Increase in 3-picoline feed rate and NH₃: 3-picoline ratio exhibited an inhibiting effect on the conversion, while an increase in air: 3-picoline ratio has no significant influence on the performance.     

Synthesis and simultaneously enhanced photovoltaic property of poly[4,4,9,9-tetra(4-octyloxyphenyl)-2,7-indaceno[1,2-b:5,6-b′]dithiophene-alt-2,5-thieno[3,2-b]thiophene]

An alternating conjugated polymer derived from 4,4,9,9-tetra(4-octyloxyphenyl)indaceno[1,2-b:5,6-b′]dithiophene and thieno[3,2-b]thiophene was synthesized by Stille coupling reaction. The copolymer shows extensive absorption from 360 nm to 590 nm with optical band gap of 2.12 eV. The highest occupied molecular orbit (HOMO) and the lowest unoccupied molecular orbit (LUMO) energy levels of the copolymer, determined by cyclic voltammetry (CV), are about ?5.29 eV and ?3.01 eV, respectively. A field-effect hole mobility of 8.1 × 10^?4 cm²/(V s) and an on/off ratio of 2.0 × 10³ are obtained in the field-effect transistors based on the copolymer. The J_sc, V_oc and FF of the polymer photovoltaic cells (PVCs) based on the copolymer were enhanced simultaneously via the inserting of alcohol soluble conjugated polymer interlayer between active layer and metal cathode, and the maximal power conversion efficiency of 4.19% was achieved in the modified devices under an AM 1.5 simulator (100 mWcm^?2).     

Facile synthesis and characterization of conducting polymer-metal oxide based core-shell PANI-Pr2O–NiO–Co3O4 nanocomposite: As electrode material for supercapacitor

Metal oxide nanoparticles and their composites with conducting polymers, specifically Polyaniline (PANI) were utilized for fabricating nanoscale supercapacitor (SC) electrode materials. In the present study, we have synthesized pristine Pr₂O₃, NiO, Co₃O₄ nanoparticles, binary PANI-Pr₂O₃, PANI-NiO, PANI-Co₃O₄, ternary Pr₂O₃–NiO–Co₃O₄, and quaternary PANI-Pr₂O₃–NiO–Co₃O₄ spherical core-shell nanocomposite using co-precipitation and ultra-sonication methods. The grown samples were characterized with different analytical techniques. The XRD pattern revealed that the as-synthesized products were crystalline with Pr₂O₃ hexagonal phase, NiO cubic phase, and Co₃O₄ cubic phase in pure and nanocomposites. The Williamson-Hall, Scherrer, and size-strain plot methods were employed to study the crystalline development and contribution of micro-strain. FTIR pattern exhibited the metal-oxygen and PANI bond vibrations. FE-SEM images shown the spherical core-shell shape morphology of quaternary nanocomposite. EDX evident the presence of praseodymium, cobalt, and nickel in synthesized samples. UV–vis spectroscopy confirmed the absorption in the visible region. The IV graphs showed a higher conductivity of quaternary nanocomposite. The cyclic voltammetry results revealed that the quaternary nanocomposite has a higher specific capacitance 500 Fg^-1 as compared to binary nanocomposites 134 F g^?1 (PANI-Pr₂O₃), 143 F g^?1 (PANI-Co₃O₄), 256 F g^?1 (PANI-NiO), and PANI (90.8 F g^?1) at a scan rate of 5 m Vs^?1. The GCD results also showed that the quaternary nanocomposite has a higher specific capacitance of 905 F g^?1 at current density 1 A g^?1 with maximum energy density and power density of 87.99 kWhkg^-1 and 2.6 k W kg^?1_, respectively. The EIS curve also confirmed that the quaternary nanocomposite has a lower polarization resistance (R_p) and solution resistance (R_s). The higher capacitance of quaternary nanocomposite can facilitate ion transfer, and the formation of its core-shell structure flourish to enhance surface-dependent electrochemical properties. Furthermore, this study gives a novel research idea to manufacture electrode materials for supercapacitors.     

Electrical conductivity and thermoelectric power studies of solution-combustion-processed Ca2.76Cu0.24Co4O9

Nanocrystalline Ca_2.76Cu_0.24Co₄O₉ powders (25 nm in crystallite size) are synthesized by the solution combustion method, using aspartic acid as the combustion fuel. In this study, we discuss the effect of sintering temperature on the microstructure and thermoelectric properties of Ca_2.76Cu_0.24Co₄O₉. The density and grain size increase with an increase in sintering temperature. The Ca_2.76Cu_0.24Co₄O₉ sintered at 900 °C shows the largest value of electrical conductivity and Seebeck coefficient, resulting in the largest power factor (3.8×10^?4 W m^?1 K^?2 at 800 °C). This value is more than 22 times larger than that of the Ca_2.76Cu_0.24Co₄O₉ sintered at 940 °C (1.7×10^?5 W m^?1 K^?2 at 800 °C).     

Enhanced performance and durability of lanthanum strontium cobalt ferrite by in-situ solvothermal modification

Due to the limitations of single material, the oxygen reduction kinetics may be slow, which is considered as a key challenge for developing the high-performance cathodes. In this work, an effective strategy is proposed, employing the in-situ solvothermal method, in which the LSCF, one of the most promising cathode materials, is decorated with Co₃O₄. After being treated at 180 °C in a neutral solution, the R_p of N-?Co₃O₄ @LSCF electrode is decreased by 37%, exhibiting reasonable stability for 120 h. Utilizing the DRT technique, finding the decorated Co₃O₄ mainly promotes the charge transfer and oxygen dissociation processes. The single cell with the N-?Co₃O₄ @LSCF cathode achieves a maximum power density of 803 mW cm^-?² at 750 °C, which is 25% higher than that for the untreated LSCF electrode. Our work demonstrates that such Co₃O₄ decorated composite obtained by the in-situ solvothermal treatment is a promising cathode material for solid oxide fuel cells.     

Ferroelectric,dielectric, magnetic,structural and photocatalytic properties of Co and Fe doped LaCrO3 perovskite synthesized via micro-emulsion route

In the present investigation, La_1-xCo_xCr_1-yFe_yO₃ (x,y = 0.0, 0.12, 0.36, 0.60) perovskite was fabricated via a facile micro-emulsion route. The synthesized perovskites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques to examine the effect of Co and Fe ions on the physico-chemical properties. The ferroelectric, dielectric, and magnetic properties of La_1-xCo_xCr_1-yFe_yO₃ were changed significantly as a function of dopants contents (Co and Fe ions). Outcomes revealed that the dielectric, ferroelectric and magnetic properties of LaCrO₃ perovskite can be tuned significantly via Co and Fe doping and La_0.40Co_0.60Cr_0.40Fe_0.60O₃ have potential for photocatalytic dye removal under (visible) light expoure. The photocatalytic activity (PCA) of the pristine LaCrO₃ and La_0.40Co_0.60Cr_0.40Fe_0.60O₃ photocatalyst was evaluated under (visible) light irradiation for crystal violet (CV) dye. Experimental results revealed that La_0.40Co_0.60Cr_0.40Fe_0.60O₃ photocatalyst degrdae almost 77.21% CV dye with the rate constant value of 0.01475 min^?1. In the presence of isopropyl alcohol (IPA) scavenger, the PCA of the La_0.40Co_0.60Cr_0.40Fe_0.60O₃ photocatalyst and rate constant value of the photocatalytic reaction decreased to 32.5% and 0.00491 min^?1, suggesting the superoxide as main active specie. Results revealed that Co and Fe doping doped material is efficient for photocatalytic presentations under solar light expoure.     

Water purification using a BiVO4/graphene oxide multifunctional hydrogel based on interfacial adsorption-enrichment and photocatalytic antibacterial activity

Photocatalytic degradation by visible light-driven generation of reactive oxygen species shows great promise for purification of environmental water. However, such degradation is limited by the low separation efficiency of photogenerated carriers and the poor adsorption capacity of the photocatalyst itself. To solve these problems, we successfully constructed and prepared a composite hydrogel (BV-GH) combining a three-dimensional network structure composed of graphene oxide and BiVO₄ to achieve the synergistic effects of adsorption enrichment and photocatalytic degradation. The results show that the amount of methylene blue and methyl orange adsorbed by BV-GH is 258.78 mg g^?1 and 217.16 mg g^?1, respectively, which is much higher than that obtained for pure BiVO₄. Due to the synergistic effect of adsorption enrichment and photocatalytic degradation, the degradation rate of the dye by BV-GH reaches 94.18% in 60 min, which is 6.98 times higher than that obtained for pure BiVO₄. Electron spin-resonance (ESR) experiments confirm that the main factor affecting the dye degradation by BV-GH is the ability to produce more ·OH and ·O₂^?, which is an important reason for the excellent antibacterial performance of BV-GH against E. coli. This work can provide further inspiration for photocatalytic technology in water purification.     

High-performance Li4Ti5−xVxO12 (0 ≤ x ≤ 0.3) as an anode material for secondary lithium-ion battery

Powders of spinel Li₄Ti_5−xV_xO₁₂ (0 ≤ x ≤ 0.3) were successfully synthesized by solid-state method. The structure and properties of Li₄Ti_5−xV_xO₁₂ (0 ≤ x ≤ 0.3) were examined by X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electronic microscope (SEM), galvanostatic charge–discharge test and cyclic voltammetry (CV). XRD shows that the V⁵⁺ can partially replace Ti⁴⁺ and Li⁺ in the spinel and the doping V⁵⁺ ion does almost not affect the lattice parameter of Li₄Ti₅O₁₂. Raman spectra indicate that the Raman bands corresponding to the Li–O and Ti–O vibrations have a blue shift due to the doping vanadium ions, respectively. SEM exhibits that Li₄Ti_5−xV_xO₁₂ (0.05 ≤ x ≤ 0.25) samples have a relative uniform morphology with narrow size distribution. Charge–discharge test reveals that Li₄Ti_4.95V_0.05O₁₂ has the highest initial discharge capacity and cycling performance among all samples cycled between 1.0 and 2.0 V; Li₄Ti_4.9V_0.1O₁₂ has the highest initial discharge capacity and cycling performance among all samples cycled between 0.0 and 2.0 V or between 0.5 and 2.0 V. This excellent cycling capability is mainly due to the doping vanadium. CV reveals that electrolyte starts to decompose irreversibly below 1.0 V, and SEI film of Li₄Ti₅O₁₂ was formed at 0.7 V in the first discharge process; the Li₄Ti_4.9V_0.1O₁₂ sample has a good reversibility and its structure is very advantageous for the transportation of lithium-ions.     

The synthesis,cyclic voltammetry and spectroelectrochemical studies of Co(II) phthalocyanines tetra-substituted at the α and β positions with phenylthio groups

Non-peripherally substituted cobalt 1,(4)-(tetraphenylthiophthalocyaninato) and peripherally substituted cobalt 2,(3)-(tetraphenylthiophthalocyaninato) complexes were synthesized. Redox processes were observed at E_1/2 = ?1.44 V (I), ?0.39 V (II), +0.37 V (III), +0.78 V (IV) and 1.15 V (V) for the non-peripherally substituted and at E_1/2 = ?1.42 V (I), ?0.57, ?0.39 V (II), +0.27 V (III), +0.79 V (IV) and +1.10 V (V) for the peripherally substituted complexes, respectively. The couples were assigned to Co^IPc^?2/Co^IPc^?3 (I), Co^IIPc^?2/Co^IPc^?2 (II), Co^IIIPc^?2/Co^IIPc^?2 (III), and Co^IIIPc^?1/Co^IIIPc^?2 (IV) using spectroelectrochemistry. The last process (V) could not be ascertained by spectroelectrochemistry but is associated with ring oxidation. Upon reduction or oxidation, the Q band of the non-peripherally substituted complex became less red shifted compared to that of its peripherally substituted counterpart.     

Holey graphene interpenetrating networks for boosting high-capacitive Co3O4 electrodes via an electrophoretic deposition process

A composite of Co₃O₄/holey graphene (Co₃O₄/HG) was prepared via a facile hydrothermal route, and was then processed into an electrode by an electrophoretic deposition process. Holey graphene (HG) wrapped Co₃O₄ to form a 3D skeleton network, thereby providing high electrical conductivity, and the holes in HG could further shorten the electrolyte ion diffusion pathway. Therefore, by adjusting the mass ratio of Co₃O₄ to HG, the Co₃O₄/HG composite afforded an enhanced capacitance of 2714 F g⁻¹ (at a current density of 1 A g⁻¹), which is 20 times higher than that of pure Co₃O₄. To further explore the practical applications of Co₃O₄/HG, a symmetric supercapacitor employing Co₃O₄/HG was fabricated. The supercapacitor functioned stably at potentials up to 1.2 V, with an enhanced energy density of 165 Wh kg⁻¹ and a high power density of 0.6 kW kg⁻¹ at 1 A g⁻¹.