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Among the environmental issues, plastic waste is one of the most significant problems, and thus, searching for ways to solve it is critical. In the present work, a green process is proposed for synthesizing RGO nanosheets from recycled plastic waste for efficient supercapacitor applications. The suggested approach consists of the transformation of plastic waste into GO using a direct and reproducible strategy and then the transformation of GO to RGO via an eco-friendly reducing agent. The synthesized RGO nanosheets possessed desirable electrochemical characteristics such as a specific capacitance of 104F/g at 0.5A/g, 90% capacitance retention after 5000 cycles, and good rate capability. The RGO nanosheets were further employed as electrode materials for the supercapacitor devices which has been evidenced with high energy density and power density. Physical properties have been characterized by XRD, Raman spectroscopy and transmission electron microscope have clearly observed the structure and the morphology of Graphene nanosheets has been established. The electrochemical properties of RGO have been examined and demonstrated to be regular. The proposed structure exhibits a nearly rectangular shape within the range of the potential window, conforming to the standard characteristics of an ideal capacitor. The findings of this study represent a viable and techno-economically feasible strategy to address the global issue of plastic waste and generate high-value graphene materials for energy storage technologies.

The development of composite materials is a key area of research for enhancing the electrochemical performance of electrode materials. In this study, NiCo–S nanostructured hybrid electrode materials were prepared on nickel foam (NF) by using binary metal–organic frameworks (MOFs) as the sacrificial template through a two-step hydrothermal method. Ni–MOF was then deposited on the surface of NiCo–S/NF through the hydrothermal method and subsequently converted into Ni(OH)₂ through a subsequent alkalization treatment. The duration of the Ni–MOF hydrothermal process was varied as a parameter. NiCo–S@Ni–MOF/NF was prepared through hydrothermal reaction for 6h, 9h and 12h, followed by heating in a 6M KOH solution at 75${}^{\circ }$C for 6h in a water bath. The electrode materials with the best morphology and electrochemical properties were obtained when the hydrothermal reaction time was 6h. The optimized electrode had a specific capacity of 2533.2F$\cdot$g${}^{-1}$ at 1A$\cdot$g${}^{-1}$ and a capacity retention rate of 60.8% at 10A$\cdot$g${}^{-1}$, which indicated good rate performance. Additionally, the electrode material demonstrated excellent cycling stability, with a capacity retention rate of 95.3% after 5000 cycles at 50mV$\cdot$s${}^{-1}$. The energy density of the hybrid supercapacitor device assembled from this electrode material was 33.5Wh$\cdot$kg${}^{-1}$ when the power density was 849.89W$\cdot$kg${}^{-1}$ at a current density of 1A$\cdot$g${}^{-1}$.

The synthesis, spectroscopic and electrochemical properties of the Lu(oepz)₂ (oepz ≡ 2,3,7,8,12,13,17,18-octakis(ethyl)-5,10,15,20-porphyrazinato) complex are reported. The complex, as inferred from UV-vis spectra recorded at different concentrations, strongly aggregates in solution, the most likely association mode being dimerization. The complex shows a weak near-IR absorption (λ_max = 834 nm) that is considerably blue-shifted compared with the near-IR absorption of bis(π-radical) lutetium analogues. The Lu(oepz)₂ neutral species is electrochemically stable between 0.73 and -0.98 V (vs Ag/AgCl), which is the largest range of stability for neutral lutetium di- tetrapyrrole complexes. Lu(oepz)₂ shows excellent Type II photodynamic activity, as indicated by the value of the singlet oxygen generation quantum yield φ_Δ of 0.94 obtained by comparison with meso-tetraphenylporphyrin.

The effects of mechanical alloying on the microstructure of binary and ternary powder mixtures with stoichiometric compositions of Mg₂Ni and Mg₂Ni_0.75Nb_0.25 were studied, respectively. Also, the electrode properties of the milled products were investigated in 6M KOH solution. X-ray diffraction and scanning electron microscopy of the milled products showed the formation of Mg₂Ni-based nanocrystallites after 15 and 10h of milling using the initial binary and ternary mixtures, respectively. It was found that partial substitution of Nb for Ni has beneficial effect on the formation kinetic of nanocrystalline Mg₂Ni. Longer milling times resulted in the formation of an amorphous phase. A relatively high discharge capacity of 350mAhg^-1 was measured for the electrode made up of the ternary milled product after 20h. Also, the ternary milled product showed longer discharge life. This ternary electrode showed a microstructure consisting of Mg₂Ni nanocrystallites and an amorphous phase. Nb substitution for Ni was found to be beneficial to electrode properties of the milled products.

In this research, LiMn₂O₄ nanopowders were synthesized via sol–gel method using gelatin as a novel chelating agent. The effect of temperature and pH on the structure, morphology and particle size of synthesized powders has been investigated by the differential thermal analysis (DTA), the X-ray diffraction (XRD), the Fourier transform infrared (FTIR) and the field-emission scanning electron microscope (FESEM). The crystal structure of LiMn₂O₄ was completely formed without any impurity phase at a calcination temperature of 750${}^{\circ }$C. The peak intensity ratio of I${}_{400}$/I${}_{311}$, which presents the stability of LiMn₂O₄ structure, is bigger for the sample with pH=4 than that of the samples with pH=7 and 8. The sample with pH=4 has smaller particles of about 70 nm, with more homogeneity and less agglomeration than that of the other samples. At calcination temperature to 850${}^{\circ }$C, the size of the particles has become bigger and the particle surfaces show more clarity in all samples. The effect of the pH value on electrochemical properties was studied by galvanostatic charge/discharge tests. The results show more capacity lost for the sample with pH=8 with regards to the other samples.

Modifications with different acids (HNO₃, H₂SO₄, HCl and HF, respectively) were introduced to treat the activated carbons (ACs) surface. The microstructures and surface chemical properties were discussed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), ASAP, Raman spectra and Fourier transform infrared (FTIR) spectra. The ACs electrode-based supercapacitors were assembled with 6 mol ⋅ L${}^{-1}$ KOH electrolyte. The electrochemical properties were studied by galvanostatic charge–discharge and cyclic voltammetry. The results indicated that although the BET surface area of modified ACs decreased, the functional groups were introduced and the ash contents were reduced on the surface of ACs, receiving larger specific capacitance to initial AC. The specific capacitance of ACs modified with HCl, H₂SO₄, HF and HNO₃ increased by 31.4%, 23%, 21% and 11.6%, respectively.

Two symmetrical TPA chromophores containing 1,3,4-oxadiazole group were designed and synthesized through the Wittig–Horner reaction. All compounds were characterized by NMR, IR, UV and melting point. Chromophore I and II showed good thermal stability and did lose less than 5% weight on heating to about 300°C. The electrochemical property was explored by cyclic voltammetry. The HOMO and LUMO energy of compound I were estimated to be -3.65 eV and -1.09 eV. That of compound II were -3.69 eV and -1.10 eV. Both chromophores exhibited a positive solvatochromic behavior. In CH₂Cl₂, the maximum peaks of single-photon-excited fluorescence (SPEF) were at 512 nm for compound I and at 495 nm for compound II with high fluorescence quantum yields 0.73 and 0.70, respectively. The two-photon-excited fluorescence (TPEF) had also been investigated. Pumped by femtosecond laser at 800 nm, strong up-conversion emissions with the central wavelength were at 532 nm for compound I and 550 nm for compound II in the solution of CH₂Cl₂.

Submicron Li_0.8CoO₂ particles were prepared by sol–gel method, and then ball-mill grinding method was adopted to make nanosized Li_0.8CoO₂ powders. The two kinds of powders were then examined by X-ray diffraction (XRD), ICP (inductively coupled plasma), the multi-point BET (Brunauer, Emmett and Teller) and transmission electron micrographs (TEM). It appeared that the Li_0.8CoO₂ nanoparticles exhibited quite different electrochemical properties, such as higher open-circuit voltage and lower discharge capacity, compared to submicron Li_0.8CoO₂ particles.

In this paper, we synthesized zinc oxide (ZnO) thin film by using a cost effective chemical bath deposition technique (CBD) at 90^∘C. The as-deposited ZnO films exhibited polycrystalline in nature. The FESEM image shows growth of nanorods about 0.2$\mu$m length. The Raman spectrum was recorded using frequency of 532nm with excited line Nd-YAG laser. The optical band gap of ZnO thin film obtained 3.37eV. The value of RMS roughness is determined by atomic force microscopy (AFM), found to be 34nm. The supercapactive studies were determined in 2MKOH aqueous electrolyte by means of cyclic voltammetry and charge–discharge technique. ZnO exhibited maximum specific capacitance of ZnO 204F/g at the scan rate of 5mV/s.

The 5-(4-carboxylatomethoxy)phenyl-10,15,20-triphenyl porphyrin (H₂Pp) and its transition metal complex (MPp, M = Zn²⁺, Co²⁺, Ni²⁺, Cu²⁺) were synthesized and characterized by IR, UV-vis, MS and elementary analysis. Electrocatalytic effects associated with the reduction of thionyl chloride in a lithium/thionyl chloride (Li/SOCl₂) battery containing H₂Pp and its transition metal complex (MPp, M = Zn²⁺, Co²⁺, Ni²⁺, Cu²⁺) are evaluated by the relative energy of the battery and discharge time. The results indicate that the energy of Li/SOCl₂ battery catalyzed by CuPp and ZnPp is 103.7%, 106.3%, respectively, higher than that of Li/SOCl₂ battery in the absence of the porphyrins. The energy of Li/SOCl₂ battery whose electrolyte contains NiPp and CoPp is similar to that of the cell in the absence of these complexes. It shows that the electronic configuration of the central metal ion influences a charge-transfer process during the reduction of thionyl chloride. With the increasing numbers of d electrons of the central metal ion, the catalytic activity of MPps was enhanced. The ZnPp with electronic configuration d¹⁰ of central metal ion exhibits relatively high catalytic activity.

A trinuclear copper(II) phthalocyanine complex was synthesized by chelate coordination of the peripherally introduced Schiff-base nitrogen and phenoxide oxygen on the Cu(pc) core to a copper(II) ion. The magnetic, spectral and electrochemical properties were compared with those of the precursor mononuclear Cu(pc) complex with the NO chelate coordination site and a mononuclear Schiff-base copper(II) complex corresponding to the central bis-chelated unit of the title trinuclear complex. A stronger aggregating nature of the trinuclear complex compared with the precursor mononuclear Cu(pc) complex was confirmed by the spectral change of the Q band feature coming from the coordination to the copper(II) ion in dichloromethane. Two successive pc-ring reduction waves were not observed for the trinuclear complex in dichloromethane containing TBP(PF${}_{\mathrm{\text{6}}})$, alternatively showing an irreversible wave in the reduction side. The central bis-chelated copper(II) ion was considered to play an important role for the redox behavior of the trinuclear complex.

Polypyrrole/manganese dioxide nanocomposite was deposited on graphite felt (GF) via electrodeposition to fabricate polypyrrole/manganese dioxide/graphite felt (PYMG), which can be used as novel free-standing electrode for supercapacitors. The microstructure and morphology of the as-prepared samples were characterized by Fourier transform infrared (FTIR) spectra, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Cyclic voltammogram (CV), chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS) techniques were employed to investigate the electrochemical performance of the composites. The PYMG electrode displayed specific capacitance as high as 596.3 Fg^-1 at the current density of 0.5 Ag^-1, which is much higher than that of polypyrrole/manganese dioxide (PPy/MnO₂) composite reported previously. The high specific capacitance of PYMG may be attributed to the fact that the porous GF is a good conductive matrix for the dispersion of PPy/MnO₂ composite and it can facilitate easy access of electrolytes to the electrode, which results in enhancement of the electrochemical performance of the composite. Furthermore, the PYMG composite exhibited enhanced specific capacitance compared to MnO₂/GF (MGF) and PPy/GF, which may be ascribed to the synergistic effect of PPy and MnO₂.

Porous hollow SnO₂ nanospheres were prepared by means of enforced Sn²⁺ hydrolysis method under hydrochloric acid medium. These hollow nanospheres with an average diameter of 220nm had a very thin shell thickness of about 40nm and were surrounded by elongated octahedral-like nanoparticles with the apex oriented outside. The experimental conditions, such as HCl content, reaction temperature and time directly dominated the morphology, structure and crystallinity of the obtained samples. A pre-oxidation-nucleation-growth mechanism and inside-out Ostwald-ripening method was proposed on the basis of the previous research and time-dependent experiments. Electrochemical tests showed that the porous hollow SnO₂ nanospheres exhibited improved cycling performance for anode materials of lithium-ion batteries, which retained a high reversible capacity of 540.0mAhg^-1, and stable cyclic retention at 120th cycle.

In this paper, hierarchical CuO/MnO₂ composite hollow nanospheres have been successfully fabricated by water evaporation-induced self-assembly through a redox transformation reaction between Cu₂O nanospheres and KMnO₄ solution at 120${}^{\circ }$C for 6h, followed by removing the residual Cu₂O cores with ammonia hydroxide solution. The outstanding feature of this method is that the reaction system is in a dynamic environment due to the evaporation of the solvent water, which benefits the self-assembly of nanostructures to form hierarchical structures. Both Kirkendall effect and Ostwald ripening mechanism are suggested to be responsible for the formation of the hierarchical CuO/MnO₂ nanocomposites according to the characterization results. The electrochemical properties of the products were studied, and the results show that the hierarchical CuO/MnO₂ hollow nanospheres exhibit high capacity and good rate performance (a stable capacity of about 480mAhg${}^{-1}$ after 80 cycles of variable charging rate), which is probably attributed to the hierarchical hollow nanostructures.

Carbon nanotubes (CNTs) were welded on the surface of thermoplastic polypropylene (PP) substrate by laser irradiation and then manganese dioxide (MnO₂) was deposited on the surface of CNTs by electrochemical method to prepare CNTs/MnO₂ flexible electrodes (L-CM). The microstructure and morphology of CNTs/MnO₂ composites were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The results showed that CNTs were welded on the surface of the substrate, adhering to each other to form a porous network structure. In addition, there were distinct small protrusions on the surface of CNTs, indicating that MnO₂ had been successfully deposited on the surface of CNTs. Cyclic voltammogram (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques were employed to investigate the electrochemical performance of the composites. Compared with CNTs/MnO₂ composite prepared via compaction (denoted as C-CM), L-CM composite prepared under the laser power of 0.75W (denoted as L-CM75) showed a larger capacitance of 214.6Fg${}^{-1}$ at the current density of 0.5Ag${}^{-1}$ and displayed excellent bendability, demonstrating capacitance retention of approximately 89.6% after 1000 bending cycles. The excellent performance of L-CM75 may be attributed to the fact that the CNTs welded on the substrate have formed an effective conductive network whose porous structure can facilitate easy access of electrolytes to the electrode, which results in enhancement of the electrochemical performance of L-CM75.

In order to reduce the negative volume effect of Silicon (Si) and Silica (SiO${}_2)$ as anode materials, CNTs@SiO₂/Si@C is prepared by sol–gel method and magnesiothermic reduction process. SEM and TEM results show that the surface of Carbon nanotubes (CNTs) is uniformly coated with active materials including SiO₂ and Si. Active materials (SiO₂/Si) closely contact with the conductive network constructed by CNTs, which greatly improves the conductivity of the composite anode material. Moreover, the large specific surface area of the tubular structure provides more Li${}^{+}$ diffusion channel. The cushion space of the hollow tube structure effectively alleviates the volume effect of SiO₂/Si and enables the anode material excellent electrochemical performance in the cycling test. The initial discharge capacity of CNTs@SiO₂/Si@C is 1064mAh/g at current density of 200 mA/g. The specific discharge capacity of CNTs@SiO₂/Si@C is higher than 960 mAh/g after 100 cycles, and the coulomb efficiency maintains over 98% in the range from 30th to 100th cycle.

Two kinds of CuO nanomaterials with different morphologies were grown directly on surface of nickel foam using electrochemical deposition technology, and their electrochemical properties were studied. The morphology of CuO at different deposition voltages (spherical and wheat spike) were observed by field emission scanning electron microscopy. The results showed that the deposition voltage is the main factor affecting the morphology of CuO. In addition, X-ray diffraction results showed that the prepared samples are CuO materials. The electrochemical properties of CuO nanostructures were studied by cyclic voltammetry, galvanostatic charge/discharge measurements and electrochemical impedance spectroscopy. These test results showed that the specific capacitance of CuO nanomaterials was largely related to the morphology of the material. Compared with CuO nanospheres thin films, wheat spike CuO thin films had a more prominent specific capacitance. The wheat spike CuO array film has a specific capacitance of 120mF/cm² at a current density of 1mA/cm² in 1mol/L sodium sulfate electrolyte.

Glycine was firstly used as a chelating agent to prepare LiFePO₄/C cathodes by the sol–gel process and sucrose as carbon source. The effects of calcination temperature on properties of LiFePO₄/C cathode were investigated using scanning electron microscope (SEM), X-ray diffraction (XRD), galvanostatic charge-discharge and cyclic voltammogram (CV) respectively. The XRD patterns indicate that all samples were of good crystallinity. The primary particle size increased with the calcination temperature from 600 to 750°C. The LiFePO₄/C sample synthesized at 700°C has the best electrochemical performance with an initial discharge capacity of 162.6 mAh g^-1 at 0.1 C and the discharge capacity remains at 154.6 mAh g^-1 after 50 cycles.

A facile synthetic approach for CoSb₃/graphene nanocomposite has been developed in this work. By adjusting Co/Sb molar ratio, reaction temperature, and reaction time, we found that nanocrystalline CoSb₃ (5–10 nm) can form at a low temperature of 180°C and a short time of only 1 h via a one-pot solvothermal route. At the same time, graphite oxide can be reduced to graphene with uniformly loaded CoSb₃ nanoparticles. The composites have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The nanocomposite shows improved cycling stability compared to bare CoSb₃.

Well-crystallized Na_0.44MnO₂ is readily synthesized via a facile NaCl-flux reaction at 850°C for 5 h. The Na_0.44MnO₂ material exhibits a well-defined nanoribbon structure with dimension of 50–100 nm in thickness and 200–500 nm in width. Electrochemical properties of as-prepared Na_0.44MnO₂ are thoroughly investigated on assembled nonaqueous Na_0.44MnO₂//Na cells using cyclic voltammetry, galvanostatic test, and electrochemical impedance spectroscopy. The results show that the Na_0.44MnO₂ nanoribbon material can deliver a high capacity of 106 mAh g^-1 with stable cycling performance over 40 cycles. In addition, it exhibits a favorable rate capability, delivering a capacity of 90 mAh g^-1 at a rate of 1 C. The high capacity retention combined with acceptable rate capability makes the Na_0.44MnO₂ a promising electrode material for advanced Na-ion batteries.