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28 December 2020, Volume 26 Issue 6

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2020, 26(6):  0-0. 

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Articles



Degradation and Thermal Characteristics of LiNi_0.8Co_0.15Al_0.05O₂/Graphite Lithium Ion Battery after Different State of Charge Ranges Cycling

WANG Cun, ZHANG Wei-jiang, HE Teng-fei, LEI Bo, SHI You-jie, ZHENG Yao-dong, LUO Wei-lin, JIANG Fang-ming

2020, 26(6):  777-788.  doi:10.13208/j.electrochem.200507

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The LiNi_0.8Co_0.15Al_0.05O₂ (NCA) cathode exhibits high energy density and large reversible capacity, which plays an essential role in the field of electric vehicles (EVs). However, low capacity retention and poor thermal stability limit its application. Few literatures are found for the capacity degradation mechanism of NCA/graphite batteries at home and abroad. The different state of charge (SOC) ranges cycle degradation behaviors of 18650-type NCA/graphite (2.4 Ah) battery were studied in this paper. The SOC ranges considered were 0% ~ 20% (low), 20% ~ 70% (medium), 70% ~ 100% (high), and 0% ~ 100% (whole). To obtain the states of the batteries being cycled in different SOC ranges, the basic characteristics of the four batteries, including capacity, incremental capacity (IC), internal resistance, and electrochemical impedance spectroscopy (EIS), were tested at 25 ^oC before and after every 100-cycle up to 400 cycles. At the same time, the surface temperature of the batteries during discharging was monitored to analyze the thermal characteristics. A detailed analysis for the IC curve of NCA/graphite was performed, making the mechanism of capacity degradation more clear. The results show that the battery life would be shortened after the whole SOC range cycling and the battery aging rate would be reduced to a certain extent upon cycled in the partial range. In addition, the battery thermal characteristic became the worst after the whole SOC range cycling, but the battery thermal performance became the best after the medium SOC range cycling. Analyzing IC data reveals that the main reason for the performance degradation of batteries in the high, medium and low SOC ranges cycling may be the loss of active lithium ions, and that in the high SOC range cycling may also include the loss of active materials and the increase of reaction internal resistance.



Numerical Simulations of Current and Temperature Distribution of Symmetrical Double-Cathode Solid Oxide Fuel Cell Stacks Based on the Theory of Electric-Chemical-Thermal Coupling

YU Cheng-rong, ZHU Jian-guo, JIANG Cong-ying, GU Yu-chen, ZHOU Ye-xin, LI Zhuo-bin, WU Rong-min, ZHONG Zheng, GUAN Wan-bing

2020, 26(6):  789-796.  doi:10.13208/j.electrochem.191105

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Solid oxide fuel cell (SOFC) is a high-efficient clean conversion device for future energy management. Because of the low antioxidant reduction ability and complex thermal stress, the structure of traditional asymmetrical thin anode-supported planar SOFC is easily to be broken under stack operating conditions. To overcome these defects, a new complete symmetrical SOFC based on double-sided cathodes was developed. To study the influences of gas flow direction and current collection mode on the cell performance inside stack, a numerical model was established by finite element method based on the theory of electro-thermo-chemo multiphysical coupling. By applying this model, the molar fraction of gas components, current density distribution and temperature distribution in the co-flow side and the counter flow side inside a stack are calculated, and the influences of the cathodic flow mode on the gas components and cell performance are discussed. In addition, the current distribution of the cell under the unilateral current collection mode is simulated, and its effect on the cell performance inside a stack is analyzed. The results show that the current density and temperature distribution on the electrolyte are affected by the flow direction and the current collection model. Large current density distributions are observed at gas inlet and outlet. The temperature distribution on the electrolyte layer under the co-flow model is more uniform than that under the counter flow direction. The average current density on the current collecting side is higher than that on the other side under the single current collection mode. It is also found that the current density and temperature distribution on the electrolyte layer can be effectively improved by reducing the resistance of cathodic cover plate. Moreover, the current collecting position will affect the path of electrons. Thus, optimization of the current collecting position can also contribute to improve the cell output performance inside a stack. This work provides a reference for improving the electric power density and operation life of the double-sided SOFC stack.



Effect of Reaction Conditions on Cu⁃Catalyzed CO2 Electroreduction

ZHU Chang, CHEN Wei, SONG Yan-fang, DONG Xiao, LI Gui-hua, WEI Wei, SUN Yu-han

2020, 26(6):  797-807.  doi:10.13208/j.electrochem.191228

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Electrochemical conversion of carbon dioxide (CO₂) driven by renewable electricity that can meet both carbon emission reduction and renewable energy utilization has been rapidly developed in recent years. Copper (Cu) catalyst has long been a promising candidate for CO₂ electroreduction applications because of its natural abundance and specific capability of producing a substantial amount of C2 products. However, various metallic Cu electrodes reported have been significantly influenced by the adsorption of certain cation/anion ions, resulting in wide-span catalytic activities and selectivity for various products. In addition, a recent report demonstrated that by virtue of gas-diffusion flow cell with Cu cathode, remarkable ethylene production was achieved in CO₂ electroreduction. It is, therefore, desirable to systematically investigate the effect of reaction conditions on the performances of Cu-catalyzed CO₂ electroreduction. Here we chose the commercial Cu particles with an average size of 600 nm as the catalyst for CO₂ electroreduction and investigated the electrocatalytic performances under various reaction conditions, including the commonly used electrolyte solutions, the different potassium hydrogen carbonate (KHCO3) concentrations, as well as H-type and gas-diffusion flow cells. The results of linear sweep voltammetry and potentiostatic CO₂ electrolysis showed that KHCO₃ as an electrolyte solution with a concentration of 0.5 mol?L^-1 offered good catalytic activities and high current densities, and the gas-diffusion flow cell could further improve the Faradaic efficiencies and partial current densities of the main products formate and CO. This work provides a fundamental insight to the electrocatalytic conversion of CO₂ reduction from the view of reaction conditions.



Pitting Behaviors of Passivated and Trans-Passivated 304 Stainless Steel

SHEN Jing, WANG Zi-ming, ZHENG Da-jiang, SONG Guang-ling

2020, 26(6):  808-814.  doi:10.13208/j.electrochem.190418

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In order to further understand the passivation and trans-passivation behaviors of 304 stainless steels, the samples were pretreated under different polarization potentials and their corrosion behaviors were investigated. It was found that the pitting potential of the untreated sample was the same as that of the sample treated with 1.1 V trans-passivation potential, while the pitting potential of the sample treated with 0.5 V passivation treatment was the highest. This observation was further verified by the SKP results. According to SEM observations, the surface of the untreated sample preserved a polishing morphology, while the surface of the 0.5 V passivation treated sample was covered by a passivation film decorated with small corrosion particles, performing good corrosion resistance. However, cracks appeared on the surface of the 1.1 V trans-passivation treated sample, leading to severe localized corrosion of the matrix and resulting in the deterioration of the trans-passivation film.



Core-Shell Structured Ru@PtRu Nanoflower Electrocatalysts toward Alkaline Hydrogen Evolution Reaction

WANG Xue-liang, CONG Yuan-yuan, QIU Chen-xi, WANG Sheng-jie, QIN Jia-qi, SONG Yu-jiang

2020, 26(6):  815-824.  doi:10.13208/j.electrochem.200223

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Water electrolysis for hydrogen production is beneficial for solving the problem of energy crisis and environmental issues. It is necessary to study highly active and cost-effective catalysts toward hydrogen evolution reaction (HER) to reduce the consumption of noble metals. Herein, we report the synthesis of core-shell structured Ru@Pt_0.24Ru nanoflowers electrocatalyst by stepwise reduction of Ru and Pt precursors in the mixture of oleylamine and benzyl alcohol at 160 ^oC. The average diameter of the resultant Ru@Pt_0.24Ru was 16.5±4.0 nm with a bulk atomic ratio between Pt and Ru of 0.24:1 and a surface ratio of 3.3:1 between Pt and Ru. Therefore, we speculate the formation of core-shell structure with Ru as the core and PtRu alloy as the shell. The performance of the electrocatalyst toward alkaline HER was tested in 1.0 mol·L ^-1 KOH aqueous solution. The Ru@Pt_0.24Ru exhibited pronounced alkaline HER activity with a small overpotential of 22 mV at 10 mA·cm ^-2, a low Tafel slope of 43 mV·dec ^-1, and a high mass activity of 5.68 A·mg ^-1_Pt+Ru at an overpotential of 100 mV, all largely surpassing commercial Pt/C (60 mV, 101 mV·dec ^-1, 1.53 A·mg ^-1_Pt). The attained Ru@Pt_0.24Ru also held outstanding long-term cycling stability. After 10,000 potential cycles from 0.1 to -0.1 V (vs. RHE), the overpotential increased to 30 mV at 10 mA·cm ^-2, while increased to 85 mV for Pt/C. The significantly improved electrochemical activity may be derived from the electronic and geometric effects of the electrocatalyst. The improvement of durability may be due to the stability of the flower-like dendritic morphology.



Preparation and Process Optimization of Cathode Materials for Lithium-Sulfur Batteries

WU Kai

2020, 26(6):  825-833.  doi:10.13208/j.electrochem.191227

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Lithium-sulfur (Li-S) batteries represent promising candidates for next-generation energy storage system due to their high energy density and low material cost. However, the industrial application of Li-S batteries remains challenges because of the shuttle effect from lithium polysulfides and the lack of facial routes for Li-S battery preparation. To solve these problems, a cathode consisting of different commercial carbon materials, namely, acetylene black (SP), Ketjen Black (KB) and carbon nanotube (CNT), with sulfur (S) is prepared separately for Li-S battery. After the process of 8-h ball milling for KB/S composite, together with the polyvinyl pyrrolidone (PVP) binder, the cathode could be controlled to yield large thickness (500 μm) and high tap density (991.65 mg·cm ^-3). Accordingly, the as-prepared Li-S pouch cell showed a high electrochemical performance with the discharge capacity up to 137.4 mA·h at the first cycle and the capacity retention up to 84% at the 10th cycle. Over all, we adopt a simple method to solve the serious and challenging problems from the perspective of industrialization in Li-S batteries. The advantages of this simple preparation technology include the optimized formula and process of positive electrode, the easily available component in industry, and the potential mass production. Furthermore, the most suitable electrode could be used to assemble Li-S pouch cell with high surface loading and high capacity. It would shed light on future development of high performance cathode in Li-S batteries, as well as other energy storage systems.



Effect of Stereotaxically-Constructed Graphene on the Negative Electrode Performance of Lead-Acid Batteries

Chen Pin-song, Hu Yi-tao, Zhang Xin-yi, Shen Pei-kang

2020, 26(6):  834-843.  doi:10.13208/j.electrochem.200306

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With the advantages of high ratio surface area, excellent conductivity and high stability, the stereotaxically-constructed graphene (SCG) material was added to the negative active material (NAM) of lead-acid battery for improving battery performance. XRD, SEM and cyclic voltammetry tests were carried out to analyze the influence of SCG on negative active material. It is found that the conversion efficiency of lead sulfate to lead in the negative active material added with SCG material was higher than that of control group, and the particle size of the lead sulfate obtained after the discharge reaction was smaller, which are favorable factors for inhibiting the irreversible sulfation of the negative active material. At the discharge rate of 0.1 C, the initial discharge capacity of the NAM with SCG added was 173.8 mAh·g ^-1, being 14% higher than that of the NAM without carbon adding (151.6 mAh·g ^-1). The cycle life under the high-rate partial-state-of charge (HRPSoC) state reached 10,889 cycles, which was 303% longer than the control one. Finally, for explaining the benefits of SCG materials in lead-acid batteries, possible mechanism is proposed as below: SCG material has a porous structure and excellent conductivity, which allows it to build a conductive network in the NAM and provides an ion channel for the electrolyte, thereby, reducing the ohmic resistance of the negative plate, improving the efficiency of material exchange in chemical reaction as well as the charge acceptance ability of the battery. Furthermore, LSV and EIS tests confirmed that the addition of SCG material would not cause serious hydrogen evolution reaction to the NAM, which can reduce the loss of electrolyte and maintain the stability of the battery. These results verify the positive effect of SCG on lead-acid battery, and show potential application prospect in lead-acid battery.



Preparations and Photoelectrochemical Performances of RGO-TiO₂ Nanotubes Arrays

ZHANG Ze-Yang, SUN Lan, LIN Chang-Jian

2020, 26(6):  844-849.  doi:10.13208/j.electrochem.200211

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Decorating TiO₂ nanotube arrays with RGO to improve the photocatalytic activity of TiO₂ nanotube arrays has been reported. For the reported RGO-TiO₂ nanotube arrays, TiO₂ nanotube arrays were prepared by anodizing the high-purity Ti foil in an organic electrolyte for multiple-step treatments, while RGO were deposited on TiO₂ nanotube arrays by using cyclic voltammetry or other electrical reduction methods. To enhance the reduction degree and the coverage of RGO on the resultant RGO-TiO₂ nanotube arrays, in this work, the one-step electrochemical anodization in hydrofluoric acid was used to fabricate TiO₂ nanotube arrays with different wall thicknesses by adjusting the distance between the cathode and anode. RGO were loaded on the surface of TiO₂ nanotube arrays by pulse electroreduction deposition. When the distances between the cathode and anode were 4 and 0.5 cm, respectively, the corresponding wall thicknesses of the as-prepared TiO₂ nanotubes were 8 and 14 nm, respectively. Compared with the RGO loaded on the thin-walled TiO₂ nanotube arrays, the RGO loaded on the thick-walled TiO₂ nanotube arrays were fully reduced and the RGO coverage was greatly improved. X-ray photoelectron spectroscopy demonstrated that the reduction degree of RGO loaded on the thick-walled TiO₂ nanotube arrays was higher than that of RGO loaded on the thin-walled TiO₂ nanotube arrays with the decrease of the oxygen content. UV-vis diffuse reflectance spectroscopy showed that the band gap of RGO-TiO₂ nanotube arrays became narrower than that of TiO₂ nanotube arrays due to the loading of RGO. The photocurrent measurements displayed that the photocurrent density of the RGO loaded thick-walled TiO₂ nanotube arrays was significantly increased accordingly, showing good light absorption properties, but also lower charge transfer resistance. The method and results presented in this work would lay a good foundation for the practical photoelectrochemical catalysis application of RGO-TiO₂ nanotube arrays.



Preparations and Sodium Storage Properties of Ni₃S₂@CNT Composite

DUAN Ming-tao, MENG Yan-shuang, ZHANG Hong-shuai

2020, 26(6):  850-858.  doi:10.13208/j.electrochem.200426

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Transition metal sulfides (TMSs)-based electrode materials with highly reversible sodium storage have attracted extensive attentions as one of the most prospective electrode materials for sodium ion batteries (SIBs). However, low cycling stability and rate property caused by large volume expansion and poor electronic conductivity during the electrochemical reaction still hamper their further practical application. In this work, in-situ encapsulated Ni₃S₂ nanoparticles in carbon nanotubes (Ni₃S₂@CNT) have been successfully fabricated as an anode material for high-performance SIBs by a one-step solid-phase calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry, and galvanostatic discharge/charge experiments and electrochemical impedance spectroscopy (EIS) were used to characterize the morphology, phase structure and electrochemical performance of the Ni₃S₂@CNT material. When evaluated as an anode material for sodium ion batteries, the Ni₃S₂@CNT composite exhibited excellent rate performance (the discharge specific capacity reached 541.6 mAh·g ^-1 at a current density of 100 mA·g ^-1, the discharge specific capacity could maintain at 274.5 mAh·g ^-1, even at a large current density of 2000 mA·g ^-1) and good cycle stability (the discharge and charge specific capacities still maintained at 374.5 mAh·g ^-1 and 359.3 mAh·g ^-1, respectively, at a current density of 100 mA·g ^-1 after 120 cycles). Remarkable cycling performance and rate capability could attribute to the synergistic effect between Ni₃S₂ nanoparticles and this unique carbon nanotube structure. The nanoscale size of the Ni₃S₂ particles could reduce the Na-ions diffusion path as well as increase the contact area between the electrode and the electrolyte. More importantly, in-situ generated carbon nanotube structure not only helped to improve the electronic conductivity of materials, but also buffered the volume effect of Ni₃S₂ nanoparticles during discharge and charge cycling. At the same time, the smart structure designed and fabrication method reported here provide a new way for in-situ preparation of high-performacne host materials for SIBs, and other high-end energy storage and conversion applications in the future.



Effect of 18-Crown-6 Additive on Chromium Electrodeposition in Ionic Liquid

WANG Yi-jie, NIU Dong-fang, ZHANG Xin-sheng

2020, 26(6):  859-867.  doi:10.13208/j.electrochem.191009

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Trivalent chromium ion (Cr³⁺) is used for electrodeposition due to its low toxicity. Electrodeposition in ionic liquids can greatly solve for hydrogen evolution problem. However,as a widely used Cr(III) precursor, chromium chloride hydrate (CrCl₃·6H₂O), still contains water. In the presence of water, Cr³⁺ will form a complex coordination structure with water molecules ([Cr(H₂O)₆]³⁺), which is a stable octahedral structure and is difficult to be directly reduced to chromium metal. Therefore, coordination agents should be added into the bath. In this work, the effect of 18-Crown-6 additive on chromium electrodeposition was investigated in CrCl₃/[BMIM]HSO₄/H₂O plating solution. The UV-Vis spectra showed that 18-Crown-6 formed a complex with Cr³⁺, destroyed the stable coordination structure formed by Cr³⁺ and water molecules, making a red shift in the maximum absorption wavelength. The cyclic voltammograms indicated that the electroreduction of Cr³⁺ occurred in a two-step process, namely, Cr³⁺ + e → Cr²⁺ and Cr²⁺ + 2e → Cr⁰. Both of the peak potential and initial reduction potential of Cr³⁺ had positive shifts by 220 mV after adding 18-Crown-6. The reason for this phenomenon was that when 18-Crown-6 was added to the plating solution, the stable structure of [Cr(H₂O)₆]³⁺ was destroyed, Cr³⁺ became more readily to be reduced, thereby, lowered the reduction potential of Cr³⁺. The EDS data showed that the chromium content in the coating was increased under the action of 18-Crown-6. The improvement indicated that 18-Crown-6 was beneficial to the chromium electrodeposition. The SEM characterizations indicated that the coating obtained in 18-Crown-6/CrCl₃/[BMIM]HSO₄/H₂O plating solution had a larger particle size. Tafel curves suggested that the corrosion resistance of chromium coating was better than that of brass substrate. The optimized process in 18-Crown-6/CrCl₃/[BMIM]HSO₄/H₂O plating solution could be proceeded at the temperature of 50 ^oC, pH of 3.5, current density of 1200 A·m^-2, and plating time of 1.5 h. The thickness of the chrome plating reached 72.5 μm and the current efficiency was 42.3%.



Synergistic Effect of Dissolving O₂ and Wavelength on the Photo-Assisted Anodic Deposition of CeO₂ Thin Films

JIN Tong-zheng, YANG Yu-meng, FAN Sheng-hui, WEI Guo-ying, ZHANG Zhao

2020, 26(6):  868-875.  doi:10.13208/j.electrochem.190719

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Cerium dioxide (CeO₂) thin films have been applied as new material in many technical fields such as solid oxide fuel cells, catalysts, UV absorbents, pharmacology, and coatings for corrosion protection of many metals and alloys. Electrodeposition is widely considered to be one of the best preparation methods for CeO₂ film. In this work, the CeO₂ films were prepared by photo-assisted anodic deposition in the bath solutions containing 0.05 mol·L^-1 cerium (III) nitrate, 0.1 mol·L^-1 ammonia acetate and 70% (V/V) ethanol onto 316L stainless steel (SS) surface. The synergistic effects of three monochromatic light wavelengths (i.e., 254 nm, 365 nm and 415 nm) and the dissolving O₂ have been discussed. The influences of dissolving O₂ and light wavelength on the electroplating behavior, morphology and structure of the CeO₂ films were studied by chronoamperometry, ellipsometry, scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. Results showed that photo-irradiation was helpful to the anodic growth of CeO₂ films. With the increase of wavelength from 254 nm to 415 nm, both the crystallinity and film thickness were decreased. Surface morphologies of the CeO₂ films on the anode were slightly affected by the wavelength. The effective light wavelengths in this study were 365 nm and 254 nm and the photon energy of 415 nm was not enough to excite electrons from the conduction band to the valence band. A small amount of oxygen had a positive effect on the photo-assisted anode electrodeposition of the CeO₂ thin film, but it would generate more CeO₂ adsorbed on the surface. In the photo electrochemical system, ethanol is usually used as a hole scavenger and O₂ is usually used as an electron scavenger. Due to the presence of ethanol in the bath, as the dissolved oxygen content increasing, O₂ would capture the photo-generated electrons which are able to produce positive effect on the deposition, leading to the slower deposition reaction.



Step-by-Step Modification of Graphite Felt Electrode for Vanadium Redox Flow Battery

LOU Jing-yuan, YOU Dong-jiang, LI Xue-jing

2020, 26(6):  876-884.  doi:10.13208/j.electrochem.190714

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As a well-known electrode material of the vanadium redox flow battery (VRFB),graphite felt electrode is the frequently-used electrode material in VRFB, and its low electrochemical activity is one of the key factors for the low power density of VRFB. In this work, we proposed a step-by-step modification method, which used KMnO₄ to oxidize graphite felt first and then placed in an activation solution to excite its reactivity, to improve the electrochemical performance of the graphite felt electrode. According to the results from cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) characterizations of the treated graphite felts, it was found that the oxidation time and the composition of the activation solution are factors affecting the electrode performance. In this paper, the charge transfer resistance of the electrode treated in the activation solution with a volume ratio of H₂SO₄:H₂O₂ = 3:1 after oxidation in KMnO₄ for 3 days, was significantly lower than that of the electrode treated by other methods, showing the lowest contact resistance (7.33 Ω·cm ²). The redox peak current density ratio (I_pa /I_pc) was closer to 1, which effectively increased the activity and reversibility of the redox reactions. In addition, the XPS data showed that the excellent electrochemical performance of the treated graphite felt might be related to the increase in the number of surface oxygen-containing functional groups. The charge/discharge testing results demonstrated that the all-vanadium redox flow battery employing the modified graphite felt electrodes exhibited the enhanced performance with higher battery efficiency and favorable discharge capacity. Moreover, the all-vanadium redox flow battery with the treated graphite felt as an electrode delivered the energy efficiency of 7.47%, which was higher than that of the untreated electrode at a current density at 100 mA·cm ^-2. Compared with heat treatment, acid treatment and electrochemical oxidation, the step-by-step modification method requires no auxiliary equipment and consumes no energy.



Preparations and Properties of Low Cost Sulfide Solid Electrolytes Li_6-xPS_5-xCl_x

YANG Na-chuan, WANG Yu, SHUAI Yi, CHEN Kang-hua

2020, 26(6):  885-889.  doi:10.13208/j.electrochem.190715

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With the shortage of energy and environmental pollution, the storage of electric energy is getting more attention all over the world. In order to improve the energy density and safety performance of batteries, uses of solid electrolyte become more and more popular. However, because the conductivity of solid electrolyte is not comparable to that of liquid electrolyte, the solid electrolyte application has certain limitations. With the efforts of researchers from various countries, there are several different solid electrolytes having better conductivity, for instance, sulfide solid electrolyte and oxide solid electrolyte. Sulfide solid electrolyte is a highly promising solid electrolyte material because of its high room temperature conductivity, good thermal stability and wide electrochemical window. It has outstanding advantages in high power and normal temperature solid state batteries. However, the application of expensive Li₂S raw materials required high-purity has been hampered. In this paper, Li_6-xPS_5-xCl_x (x = 0.5) solid electrolyte was prepared by ball milling using low-cost raw materials such as elemental lithium metal (99.9%), sublimed sulfur (CP), P₂S₅ (AR) and LiCl (AR). The as-prepared Li_6-xPS_5-xCl_x solid electrolyte powder was characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), and the cold-pressed Li_6-xPS_5-xCl_x tablets were tested for cycle performance and electrical conductivity in Li_6-xPS_5-xCl_x/Li half-cell. The results showed that through the pressure-free sintering at 550 ^oC, the total lithium-ion conductivity of the solid electrolyte at room temperature was 8.29×10 ^-4 S·cm ^-1, making commercialization of solid-state batteries possible.



Electrochemical Determination of Dopamine Based on Metal-Substituted Polyoxometalates Composites

XING Yi-fei, LI Na, WEN Xiao-fang, HAN Hong-yan, CUI Min, ZHANG Cong, REN Ju-jie, JI Xue-ping

2020, 26(6):  890-899.  doi:10.13208/j.electrochem.190716

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In this report, a dopamine electrochemical sensor based on metal-substituted polyoxometalates and reduced graphene oxide (RGO) composite was successfully constructed. The K₂H₂SiW₁₁NiO₃₉·xH₂O (SiW₁₁Ni) was synthesized by hydrothermal method, while the RGO was prepared by Hummers' method and chemical reduction method. The above-mentioned materials were characterized by SEM, FTIR and XRD. The as-synthesized SiW₁₁Ni and RGO composites were modified on the surface of glassy carbon electrode (GCE) by drop coating method, and the sensing interface (SiW₁₁Ni-RGO/GCE) was successfully constructed. The electrochemical properties of the sensing interface were studied by electrochemical impedance spectroscopy and cyclic voltammetry. After optimizing the experimental conditions, dopamine could be quantitatively detected by cyclic voltammetry with good performance. The limit of detection was 3.2 μmol·L ^-1 (S/N = 3), the sensitivity was 9.71 μA·(μmol·L ^-1·cm ^-2) ^-1, and the linear range was 10 to 80 μmol·L ^-1.



Novel Electrochemical Sensor Based on Integration of Nanoporous Gold with Molecularly Imprinted Polymer for Detection of Arsenic Ion(III)

MA Wu-wei, CHANG Qi-gang, SHI Xiong-fang, TONG Yan-bin, ZHOU Li, YE Bang-ce, LU Jian-jiang, ZHAO Jin-hu

2020, 26(6):  900-910.  doi:10.13208/j.electrochem.191221

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Arsenic, a toxic chemical element, is detrimental to environment and human health in particular. Therefore, the development of simple, fast, and accurate arsenic ion (As³⁺) detection methods has attracted extensive attention. In this work, an electrochemical sensor based on molecular imprinted polymer (MIP) and nano-porous gold (NPG) modified indium tin oxide (ITO) electrode (MIP/NPG/ITO) was developed for determination of As³⁺ in water with different quality. NPG with high conductivity, large specific surface area and high biocompatibility was prepared in situ on ITO surface by a green electrodeposition method using simple and controllable steps. Then, a layer of MIP was synthesized in situ on NPG surface by electropolymerization, in which As³⁺ was used as a template molecule and mphenylenediamine as a functional monomer. The preparation process of MIP/NPG/ITO was monitored by scanning electron microscope (SEM) and energy-dispersive X-ray spectroscope (EDS). The potassium ferricyanide and potassium ferrocyanide chelates were used as electrochemical probes to generate signals. The electrochemical behavior of MIP/NPG/ITO was studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). After optimizing the experimental conditions, As³⁺ was quantitatively detected by cyclic voltammetry. The linear range of As³⁺ was measured from 2.0 ×10^-11 to 9.0×10^-9 mol·L^-1, and the lower detection limit was 7.1×10^-12 mol·L^-1 (S/N = 3). The detection limit of the constructed sensor is far below 10 ppb, which meets the drinking water standards set by the World Health Organization (WHO) and Environmental Protection Agency (EPA). In addition, the sensor has the advantages of simple preparation, simple procedure of determination, good repeatability, excellent reproducibility and stability. It is worth mentioning that the prepared sensor has been successfully applied to the As³⁺ measurements of four water qualities, including landscape river water, groundwater, tap water and domestic sewage. It can be predicted that the reported simple and cheap sensor has potential practical applications in environmental monitoring, food analysis and clinical diagnosis.

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2020, 26(6):  911-913. 

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Contents

2020, 26(6):  914-920. 

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Author Index

2020, 26(6):  921-924. 

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