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.     

Selectively attaching Pt-nano-clusters to the open ends and defect sites on carbon nanotubes for electrochemical catalysis

Pt nano-clusters (nano-Pt) have been selectively attached to the open ends and defect sites of mildly oxidized multi-wall carbon nanotubes (MWCNTs) on a glassy carbon electrode (GCE) by a cyclic voltammetry (CV) electrodeposition method. The nano-Pt functionalized MWCNTs were characterized by XPS, XRD, FE-SEM and electrochemical techniques. The catalytic activity of the nano-Pt functionalized MWCNTs were tested by an oxygen reduction reaction (ORR) and a methanol oxidation reaction (MOR). Taking the ORR as an example, we found that the electrocatalytic activity of the nano-Pt functionalized MWCNTs can be well tuned by varying the cycle number and the PtCl₆²⁻ concentration of the deposition conditions. The average size of the nano-Pt was 123 nm, and it was constituted of nano-crystallite of an average size of 10.8 nm. Though the large nano-Pt particles (100-150 nm) were only attached on the open ends and defect sites of the MWCNTs, which were very different from the highly dispersed small Pt nanoparticles (<10 nm) on carbon nanotubes reported by other research groups. In our method, excellent electrocatalytic activity of the nano-Pt functionalized MWCNTs for ORR and MOR can be obtained. The mechanisms for nano-Pt deposition are proposed.     

纳米FePt/GC催化剂的制备及其对乙醇的电氧化性能

通过循环伏安法(CV)在玻碳(GC)表面电沉积出分布较为均匀的纳米Fe粒子,制得纳米Fe/GC,再经置换反应制得具有Fe核Pt壳结构的纳米粒子(纳米FePt/GC)。SEM图像显示,纳米Fe/GC和纳米FePt/GC表面粒子的形貌均呈立方体,且分布较为均匀。纳米FePt/GC对乙醇的氧化具有很高的电催化活性。相对于纳米Pt/GC催化剂,纳米FePt/GC催化剂的起始氧化电位(Ei)提前了0.044V;其对乙醇氧化的峰电流密度(jp)大约是纳米Pt/GC催化剂的2.16倍。     

Preparation and properties of Co<Subscript>3</Subscript>O<Subscript>4</Subscript> nanorods as supercapacitor material

Co₃O₄ nanorods have been successfully synthesized by thermal decomposition of the precursor prepared via a facile and efficient microwave-assisted hydrothermal method, using cetyltrimethylammonium bromide (CTAB) with ordered chain structures as soft template for the first time. The obtained Co₃O₄ was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical measurements. The results demonstrate that the as-synthesized nanorods are single crystalline with an average diameter of about 20 to 50 nm and length up to several micrometers. Preliminary electrochemical studies, including cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) measurements, are carried out in 6 M KOH electrolyte. Specific capacitance of 456 F g⁻¹ for a single electrode could be achieved even after 500 cycles, suggesting its potential application in electrochemical capacitors. This promising method could provide a universal green chemistry approach to synthesize other low-cost and environmentally friendly transition metal hydroxide or oxide.     

Capacitive properties of promising energy storage material based on thiophene containing perylenediimide polymer

In this study, electropolymerization of pre-synthesized N,N′-di-[3-[2-(3-thienyl)ethyl] phenyl] perylene-3,4,9,10-bis(dicarboximide) (ThPDITh) was performed on Au button electrode and the properties of the resultant polymer P(ThPDITh) were investigated by electrochemical techniques. Effect of the polymerization charge on the redox behaviors of the polymer film was investigated by cyclic voltammetry (CV) and the polymer film was further characterized by electrochemical impedance spectroscopy (EIS) measurements. Corresponding electrical equivalent circuit was applied to the experimental data to explain the electrochemical phenomenon on the interface of the Au/P(ThPDITh). In order to obtain information on the energy storage properties of P(ThPDITh) as a pseudo-capacitive electrode material, important cell characteristics, such as redox process in anodic and cathodic potential ranges, stability of galvanostatic charge–discharge (GCD) curves, coulombic efficiency, capacitance, energy and power density values were determined. Capacitance values, obtained through different measurements (CV, EIS and GCD) are all in good agreement with each other. All the results suggested that P(ThPDITh) is capable of undergoing multiple reversible redox processes, and a good candidate for improving the capacitance and energy density of electrode material while still offering high power capability.     

High surface area LaNiO<Subscript>3</Subscript> electrodes for oxygen electrocatalysis in alkaline media

LaNiO₃ coatings on nickel-foam supports were prepared by brush painting. The electrochemical properties were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Comparative studies were performed with LaNiO₃-pelleted electrodes. The roughness factors were determined by CV and found to be 5,208 ± 350 and 4,037 ± 250 for the pelleted and coated electrodes, respectively. EIS measurements confirm the results obtained by CV. Values lower than 0.3 were calculated for the morphology factors for both electrodes, indicating low electrochemical porosity. The experimental method used in this work to synthesise the oxide coupled with the use of Ni foam as support has proved to be very effective in producing oxide electrodes with surface areas higher than those referred to in relevant literature.     

层间阴离子对铝取代氢氧化镍电化学性能的影响

采用化学共沉淀法制备出层间分别含有SO42-和NO3-的铝取代氢氧化镍样品。利用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)和扫描电子显微镜(SEM)对样品的微观结构和表面形貌进行了分析。采用循环伏安(CV)、交流阻抗(EIS)和充放电测试表征了样品的电化学性能。结果表明,层间含有NO3-的铝取代氢氧化镍比层间含有SO2-的铝取代氢氧化镍具有更好的电化学反应可逆性、更高的质子传递系数和放电比容量。     

Preparation and electrochemistry of NiO/SiNW nanocomposite electrodes for electrochemical capacitors

This paper studies nickel oxide/silicon nanowires (NiO/SiNWs) as composite thin films in electrodes for electrochemical capacitors. The SiNWs as backbones were first prepared by chemical etching, and then the Ni/SiNW composite structure was obtained by electroless plating of nickel onto the surface of the SiNWs. Next, the NiO/SiNW nanocomposites were fabricated by annealing Ni/SiNW composites at different temperatures in an oxygen atmosphere. Once the electrodes were constructed, the electrochemical behavior of these electrodes was investigated with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). In 2 M KOH solution, the electrode material was found to have novel capacitive characteristics. Finally, when the NiO/SiNW composites were annealed at 400 °C, the maximum specific capacitance value was found to be as high as 681 F g⁻¹ (or 183 F cm⁻³), and the probing of the cycling life indicated that only about 3% of the capacity was lost after 1000 charge/discharge cycles. This study demonstrated that NiO/SiNW composites were the optimal electrode choice for electrochemical capacitors.     

Inhibition of steel corrosion by electrosynthesized poly(o-anisidine)-dodecylbenzenesulfonate coatings

Poly(o-anisidine)-dodecylbenzenesulfonate (POA-DBSA) coatings were synthesized on stainless steel from aqueous solution containing o-anisidine and dodecylbenzene sulfonic acid by using cyclic voltammetry. These coatings were characterized by Fourier transform infrared spectroscopy (FTIR), UV-vis absorption spectroscopy, scanning electron microscopy (SEM) and cyclic voltammetry (CV). Corrosion tests of these coatings were carried out in aqueous 3% NaCl solution by using open circuit potential (OCP) measurements, potentiodynamic polarization technique, cyclic potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS). The results reveal that POA-DBSA acts as a corrosion protective coating on steel and reduces the corrosion rate (CR) of steel almost by a factor of 14.5.     

Electropolymerization, characterization and corrosion performance of poly(N-ethylaniline) on copper

Poly(N-ethylaniline) (PNEA) coatings were grown by cyclic voltammetry technique on copper from 0.1 M N-ethylaniline (NEA) in 0.3 M oxalic acid solution. The optimum conditions (e.g. upper potential limit, scan rate and cycle number) effect on corrosion performance of synthesized PNEA films were determined in order to obtain best protection results against corrosion. The electrodeposited coatings were characterized by cyclic voltammetry (CV), Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy and scanning electron microscopy (SEM). Redox parameters were found after electrochemical tests and results of stability tests of these films impart an electroactive behavior that is composed of both diffusion control and thin film behavior. In addition, corrosion performance of PNEA coatings were investigated in 0.1 M H₂SO₄ by Tafel extrapolation and electrochemical impedance spectroscopy (EIS) techniques.     

Luminescence,Paramagnetic, and Electrochemical Properties of Copper Oxides-Decorated TiO2/Graphene Oxide Nanocomposites

The properties of newly synthesized Cu₂O/CuO-decorated TiO₂/graphene oxide (GO) nanocomposites (NC) were analyzed aiming to obtain insight into their photocatalytic behavior and their various applications, including water remediation, self-cleaning surfaces, antibacterial materials, and electrochemical sensors. The physico-chemical methods of research were photoluminescence (PL), electron paramagnetic resonance (EPR) spectroscopy, cyclic voltammetry (CV), and differential pulse voltammetry (DPV). The solid samples evidenced an EPR signal that can be attributed to the oxygen-vacancy defects and copper ions in correlation with PL results. Free radicals generated before and after UV-Vis irradiation of powders and aqueous dispersions of Cu₂O/CuO-decorated TiO₂/GO nanocomposites were studied by EPR spectroscopy using two spin traps, DMPO (5,5-dimethyl-1-pyrroline-N-oxide) and CPH (1-hydroxy-3-carboxy-2,2,5,5-tetramethylpyrrolidine), to highlight the formation of hydroxyl and superoxide reactive oxygen species, respectively. The electrochemical characterization of the NC modified carbon-paste electrodes (CPE) was carried out by CV and DPV. As such, modified carbon-paste electrodes were prepared by mixing carbon paste with copper oxides-decorated TiO₂/GO nanocomposites. We have shown that GO reduces the recombination process in TiO₂ by immediate electron transfer from excited TiO₂ to GO sheets. The results suggest that differences in the PL, respectively, EPR data and electrochemical behavior, are due to the different copper oxides and GO content, presenting new perspectives of materials functionalization.     

离子液体BMIMBF4对全钒液流电池正极电解液的影响

为提高全钒液流电池的能量密度和正极电解液稳定性,采用循环伏安、交流阻抗等方法,研究了1-丁基-3-甲基咪唑四氟硼酸盐（BMIMBF₄）作为正极电解液添加剂对溶液稳定性和电化学反应活性的影响,并对其机理进行了初步探讨。实验结果表明,添加BMIMBF₄后,正极电解液中五价钒离子的稳定性显著提高,电解液的电化学反应活性也有所提升。当添加量为1%时,电池的单位体积电容量比有所增加,并且能量效率有所提升。     

苯甲醇在Cu-PTFE复合电极上的电化学氧化行为

采用复合电镀制备Cu—PTFE疏水性复合电极并应用于苯甲醇的电化学氧化的研究。实验中分别测定了极化曲线、循环伏安和交流阻抗等电化学特征参数。结果表明,苯甲醇在Cu—PTFE疏水性复合电极上的电氧化电流效率为41．8％,苯甲醛的产率为83．1％,其电化学过程可能受电荷传递和浓差扩散过程综合控制。     

Polyaniline-SrTiO3 nanocube based binary nanocomposite as highly stable electrode material for high performance supercapaterry

The current study demonstrates the simplistic approach for the synthesis of SrTiO₃ nanocubes incorporated polyaniline flakes (PANI-SrTiO₃) by facile in-situ oxidative polymerisation route. The synthesised nanocomposites were characterised by various spectroscopic and surface analysis techniques viz. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and Brunauer-Emmett-Teller analysis (BET). The electrochemical performance of the prepared nanocomposites for energy storage application was evaluated by electrochemical impedance spectroscopy (EIS), galvanostatic charge-discharge (GCD) and cyclic voltammetry (CV) in 1?M of KOH as an electrolyte. The electrochemical investigations demonstrate that the performance of the PANI-SrTiO₃ nanocomposite in terms of rate capability was significantly higher as compared to the polyaniline flakes and SrTiO₃ nanocubes. Supercapattery was fabricated by combining activated carbon and PANI-SrTiO₃-250 as negative and positive electrodes respectively in order to evaluate complete device performance. It is found that fabricated supercapattery gave an energy density of 13.2?W?h/kg at a power density of 299?W/kg. Additionally, the fabricated supercapattery also offered excellent stability cycle with 114% capacity retention after 4000 cycles. Moreover, the performance of PANI-SrTiO₃-250 was found to be better than the other compositions.     

Using gold nanorods to enhance the current response of a choline biosensor

This present work describes the utilization of gold nanorods to create a highly responsive choline biosensor. Choline biosensors have been formed with choline oxidase (ChOx) immobilized in composite immobilization membrane matrix, which is composed of Au nanorods and polyvinyl alcohol (PVA) by a sol–gel method. Circular dichroism (CD) shows that the secondary structure of ChOx was preserved after conjugating with Au nanorods. The cyclic voltammograms (CVs) and electrochemical impedance spectroscopy (EIS) give the evidence that gold nanorods can improve the electrical conductivity of PVA-modified enzyme electrode. A set of experimental results indicates that the current response of modified electrode is several times larger than that without nanorods. The experimental conditions of biosensors are optimized, and the performance of the obtained electrodes with respect to linear range, reproducibility, response time, and stability is also presented.     

添加剂对钒液流电池正极液的影响

研究了添加剂酒石酸、乙二酸、柠檬酸、葡萄糖对钒电池正极液电化学性能和稳定性的影响,并对其规律和机理进行了探讨。CV研究结果表明:含有多个-OH的有机物葡萄糖能明显提高正极液的阳极峰电流,含有多个-COOH的乙二酸能明显提高正极液的阴极峰电流,而含有多个-OH和多个-COOH的酒石酸对正极液的阴、阳极峰电流均有明显提高。同时,酒石酸(含氧官能团-OH和-COOH)能与5价钒作用,阻碍钒离子聚合,从而提高了5价钒的稳定性。交流阻抗测试表明,正极液中添加酒石酸能大大降低电荷传递电阻和溶液电阻,电解液的性能得到了显著提高。     

Corrosion protection of mild steel by polypyrrole phosphate composite coating

Electrodeposition of polypyrrole phosphate (PPy–P) on mild steel (ST₁₂) was achieved in oxalic acid medium using cyclic voltammetry (CV) technique. Adherent and homogeneous PPy–P films were obtained. The corrosion behavior of mild steel with phosphate (PPy–P) coatings in 3.5% NaCl solutions was investigated through potentiodynamic polarization technique, open circuit potential–time curves, and electrochemical impedance spectroscopy (EIS). Based on a physical model for the corrosion of mild steel composite, the Zview (II) software was applied to the EIS to estimate the parameters of the proposed equivalent circuit. It was found that the PPy–P coatings could provide much better protection than PPy. The effect of phosphate on the morphology and structure of the passive film was investigated by scanning electron microscopy and electron dispersion X-ray analysis (EDX). The results reveal that the PPy–P coated electrode provided a noticeable enhancement of protection against corrosion process.     

Electrochemical impedance spectroscopy of poly(N-methyl pyrrole) on carbon fiber microelectrodes and morphology

This work reports the supercapacitive properties of electrochemically grown homopolymer films on carbon fiber microelectrode (CFME) via poly(N-methyl pyrrole) (P(NMPy)) which is characterized by cyclic voltammetry (CV), Fourier transform infrared reflectance (attenuated total reflection) spectroscopy (FTIR-ATR), scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). Microporosity of P(NMPy) electrocoated carbon fiber microelectrodes facilitated improved capacitance and redox behaviours by applying different DC potentials in electrochemical impedance spectroscopic measurements. The capacitance values of P(NMPy)/CFME is obtained (0.059 F) which is in the range of manufactured values.     

Electrochemical performances of nanostructured vanadium oxides

Vanadium oxide nanotubes (VOx-NTs) and nanourchin (4-phenylbutylamine/vanadium oxide) have been synthesized via one-step hydrothermal treatment. Compounds were analyzed through X-ray powder diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). CV curves illustrate reversible redox behavior with charge-discharge cycling corresponding to the reversible lithium intercalation/deintercalation. The EIS spectra were carried out in order to investigate the Li⁺ insertion mechanism at the electrode/electrolyte interface and evaluate the diffusion of Li⁺ within the bulk of cathode material.