Journal of The Electrochemical Society
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Published By The Electrochemical Society

1945-7111, 0013-4651

Author(s):  
Jéssica Santos Gomes ◽  
Érica Abadia Da Costa ◽  
Rodrigo A. A. Munoz ◽  
Alberto De Oliveira ◽  
Raquel M. F. Sousa

Abstract Most electrochemical sensors reported for catechin determination in herbal medicines actually involve the detection of not only catechins but also other flavonoids. This work proposes a strategy to selectively detect and quantify flavan-3-ol, known as catechins, in the presence of other flavonoids by complexation with AlCl3. Flavonoids (e.g.,rutin, quercetin) form stable complex with AlCl3 which affect the electrooxidation of these molecules. Hence, the electrochemical oxidation of catechin is free from the interference of other flavonoids as shown by differential-pulse voltammetry using glassy-carbon electrode. The approach was applied to herbal medicines and mass-spectrometry confirmed the presence of catechins in such samples.


Author(s):  
Wei Xu ◽  
Connor Welty ◽  
Margaret R. Peterson ◽  
Jeffrey Read ◽  
Nicholas Paul Stadie

Abstract Graphite is, in principle, applicable as a high-power anode in lithium-ion batteries (LIBs) given its high intralayer lithium diffusivity at room temperature. However, such cells are known to exhibit poor capacity retention and/or undergo irreversible side reactions including lithium plating when charged at current rates above ~2C (~740 mA g-1). To explore the inherent materials properties that limit graphite anodes in rapid-charge applications, a series of full-cells consisting of graphite as the anode and a standard Li[Ni0.8Mn0.1Co0.1]O2 (NMC811) cathode was investigated. Instead of a conventional cathode-limited cell design, an anode-limited approach was used in this work to ensure that the overall cell capacity is only determined by the graphite electrode of interest. The optimized N:P capacity ratio was determined as N/P = 0.67, enabling stable cycling across a wide range of charging rates (4-20C) without inhibition by the NMC811 cathode. The results show that unmodified, highly crystalline graphite can be an excellent anode for rapid-charge applications at up to 8C, even with a standard electrolyte and NMC811 cathode and in cells with 1.0 mAh cm-2 loadings. As a rule, capacity and specific energy are inversely proportional to crystallite size at high rates; performance can likely be improved by electrolyte/cathode tuning.


Author(s):  
Toby Bond ◽  
Roby Gauthier ◽  
Ahmed Eldesoky ◽  
Jessie Harlow ◽  
Jeff R Dahn

Abstract Single-crystal LiNixMnyCozO2 (NMC) materials have recently garnered significant academic and commercial interest as they have been shown to provide exceptional long-term charge-discharge cycling stability in Li-ion cells. Understanding the degradation mechanisms occurring in conventional polycrystalline NMC materials in comparison to the more stable single-crystal equivalents has become a topic of significant interest. In this study, we demonstrate how multi-scale, in-situ computed tomography can be used to characterize important changes occurring in wound pouch cells containing polycrystalline or single-crystal NMC. These changes include cell-level phenomena (such as deformation of the jelly roll and electrolyte depletion) as well as electrode-scale phenomena (such as electrode thickness growth and electrode cracking). A set of twenty-one cells were scanned in total, consisting of three different electrodes: polycrystalline NMC622, single-crystal NMC811, and single-crystal NMC532. These studies were designed to characterize the effects of varying C-rate, depth of discharge, and duty cycle, so this work includes an analysis of these factors as they relate to physical changes taking place at the cell and electrode level.


Author(s):  
Roby Gauthier ◽  
Aidan Luscombe ◽  
Toby Bond ◽  
Michael Bauer ◽  
Michel Johnson ◽  
...  

Abstract Lithium-ion cells testing under different state of charge ranges, C-rates and cycling temperature have different degrees of lithium inventory loss, impedance growth and active mass loss. Here, a large matrix of polycrystalline NMC622/natural graphite Li-ion pouch cells were tested with seven different state of charge ranges (0-25, 0-50, 0-75, 0-100, 75-100, 50-100 and 25-100%), three different C-rates and at two temperatures. First, capacity fade was compared to a model developed by Deshpande and Bernardi. Second, after 2.5 years of cycling, detailed analysis by dV/dQ analysis, lithium-ion differential thermal analysis, volume expansion by Archimedes’ principle, electrode stack growth, ultrasonic transmissivity and x-ray computed tomography were undertaken. These measurements enabled us to develop a complete picture of cell aging for these cells. This then led to an empirical predictive model for cell capacity loss versus SOC range and calendar age. Although these particular cells exhibited substantial positive electrode active mass loss, this did not play a role in capacity retention because the cells were anode limited during full discharge under all the tests carried out here. However, the positive electrode mass loss was strongly coupled to positive electrode swelling and electrolyte “unwetting” that would eventually cause dramatic failure.


Author(s):  
CHUAN HU ◽  
Ho Hyun Wang ◽  
Jonghyeong Park ◽  
Haemin Kim ◽  
Nanjun Chen ◽  
...  

Abstract We systematically study anion exchange membrane fuel cells (AEMFCs) based on poly(aryl-co-aryl piperidinium) (c-PAP) copolymers and provide a scalable scenario for high-performance AEMFCs, covering the optimization of the relative humidity (RH), catalyst species, catalyst interfaces, and hydrophobic treatment. Specifically, high-water-permeable c-PAP ionomers in the presence of moderate relative humidity (RH) (75%/100%) can be used to address anode flooding and cathode dry-out issues. The composition of the catalyst layer and the anode hydrophobic treatment significantly impact the power density of AEMFCs. c-PAP-based AEMFCs with optimum catalyst composition achieve a peak power density (PPD) of 2.70 W cm-2 at 80 oC in H2-O2 after hydrophobic treatment. Pt1Co1/C cathode-based AEMFCs reach a PPD of 1.80 W cm-2 along with an outstanding specific power of 13.87 W mg-1. Moreover, these AEMFCs can be operated under a 0.2 A cm-2 current density at 60 oC for over 300 h with a voltage decay rate of ~300 μv h-1.


Author(s):  
Qiao Jing Lin ◽  
Jing Mei Wang ◽  
Jian Hua Chen ◽  
Qian Yang ◽  
Li Jun Fang ◽  
...  

Abstract MoS2, a typical two-dimensional transition metal sulfide nanomaterial, has attracted much attention for supercapacitor electrode materials due to its high theoretical capacity. Herein, MoS2 nanosheets growing on a hierarchical porous carbon (HPGC) derived from pomelo peel are prepared via hydrothermal method. The curled MoS2 nanosheets uniformly grow and distribute on the conductive hierarchical porous carbon matrix, which made the electrodes materials possess a high specific surface area (320.2 m2/g). Simultaneously, the novel structure enhances the conductivity of MoS2, alleviates capacity attenuation and guarantees the interface stability. Furthermore, the MoS2/HPGC show a great enhancement in supercapacitor performance and deliver a remarkable specific capacitance of 411.4 F/g at the current density of 0.5 A/g. The initial capacitance retention rate is approximately 94.3% after 2000 cycles. It turns out that the synergistic effects between the MoS2 nanosheets and HPGC contribute to high specific capacity, excellent rate performance and ultra-long cycle life. This work provides a new idea for the design and development of MoS2 composites as the electrode materials of supercapacitors.


Author(s):  
Noufal Merukan Chola ◽  
Vikram Singh ◽  
Vivek Verma ◽  
Rajaram K Nagarale

Abstract Aqueous zinc batteries are increasingly gaining attention of the researchers in recent years because of their environmental and user friendliness as well as the economic benefits of the zinc metal. Herein we report a ferrocene based organic cathode synthesized by following green chemistry principle and stabilized by low temperature thermal encapsulation in multiwalled carbon nano tubes (MWCNTs) for stable electrochemical performance. Successful intercalation was confirmed by XRD, Raman, FTIR spectra, TEM-HAADF imaging. Without encapsulation, material exhibited initial capacity of 64.7 mAhg-1 which was drastically faded with time due to dissolution of active material. However, by low temperature thermal encapsulation, the capacity was remarkably improved to 71.3 mAhg-1 with 94% columbic efficiency and 91% capacity retention at a current density of 75mAg-1 in a 100 charge/discharge cycles. The stability of the electrode has been explained on the basis of a friendly host-guest interaction between CNTs and the organic molecules by π-π stacking, dipole-dipole and dipole induced dipole interactions with detailed electrochemical and spectroscopic characterization. From this study we conclude that the thermal intercalation in MWCNTs has been found to be excellent method to stabilize the electrode materials in battery application.


Author(s):  
Xiaoyang Dong ◽  
Jinxing Wang ◽  
Xiao Wang ◽  
Jingdong Yang ◽  
Ling Zhu ◽  
...  

Abstract Developing efficient, durable, and cost-effective non-noble metal catalysts for oxygen reduction reaction (ORR) is necessary to promote the efficiency and performance of Mg-air batteries. Herein, the Co3O4/CuO nanoparticles were synthesized by a low-cost and simple approach using CuCo-based prussian blue analogue (PBA) as precursor of pyrolysis at different calcination temperatures. It was found that the Co3O4/CuO nanoparticles calcined at 600ºC (CCO-600) have relatively small size and superior ORR performance. The onset potential is 0.889 V and the diffusion limiting current density achieves 6.746 mA·cm-2, as well as prominent stability in 0.1 M KOH electrolyte. The electron transfer number of the CCO-600 is 3.89 under alkaline medium, which indicates that the reaction mechanism of ORR is dominated by 4 e process, similar to commercial Pt. The primary Mg-air battery with the CCO-600 as the cathode catalyst has been assembled and possesses better discharge performance than the CuCo-based PBA. The open circuit voltage of CCO-600 arrives at 1.76 V and energy density of 1895.95 mWh/g. This work provides an effective strategy to develop non-noble metal ORR catalyst for the application of metal-air batteries


Author(s):  
Abolfazl Darroudi ◽  
Saeid Nazari ◽  
Seyed Ali Marashi ◽  
Mahdi Karimi-Nazarabad

Abstract An accurate, rapid, simple, and novel technique was developed to determine simvastatin (SMV). In this research, a screen-printed electrode (SPE) was deposited with graphene oxide (GO) and sodium dodecyl sulfate (SDS), respectively. For the first time, the handmade modified SPE measured the SMV by differential pulse voltammetry (DPV) with high sensitivity and selectivity. The results of cyclic voltammetry indicated the oxidation irreversible process of SMV. Various parameters (pH, concentration, scan rate, support electrolyte) were performed to optimize the conditions for the determination of SMV. Under the optimum experiment condition of 0.1 M KNO3 as support electrolyte and pH 7.0, the linear range was achieved for SMV concentration from 1.8 to 36.6 µM with a limit of detection (LOD), and a limit of quantitation (LOQ) of 0.06 and 1.8 µM, respectively. The proposed method was successfully utilized to determine SMV in tablets and urine samples with a satisfactory recovery in the range of 96.2 to 103.3%.


Author(s):  
Jerome R ◽  
Brahmari Shetty ◽  
Dhanraj Ganapathy ◽  
Preethika Murugan ◽  
Raji Atchudan ◽  
...  

Abstract Modification of anodes with highly biocompatible materials could enhance bacterial adhesion, growth, and improve the rate of electron-transfer ability in microbial fuel cells (MFCs). As such, there has been increasing interest in the development of innovative anode materials to prepare high-performance MFCs. We report the synthesis of poly(3,4-ethylene dioxythiophene):poly(4-styrene sulfonate) (PEDOT:PSS) doped with thermally expanded graphite (TEG) composite coated carbon felt (CF) as anode for MFCs. For this purpose, as-synthesized PEDOT:PSS/TEG composite was characterized using high-resolution scanning electron microscopy (HR-SEM), and Raman and Fourier transform infrared (FT-IR) spectroscopies which indicated successful incorporation of TEG within PEDOT:PSS film. Furthermore, the electrochemical activity of the PEDOT:PSS/TEG coated CF was employed as the anode in the MFCs with sewage water as an anolyte. PEDOT:PSS/[email protected] anode exhibited higher ion-transfer ability, superior bio-electrochemical conductivity, and excellent capacitance. Using the PEDOT:PSS/[email protected] anode, we have constructed MFCs which exhibited good power (68.7 mW/m2) and current (969.3 mA/m2) densities compared to the unmodified CF based anode. The reliability of the MFCs performance was also investigated by testing three independently prepared MFCs with PEDOT:PSS/[email protected] anodes which all showed a constant voltage (~540 mV) due to the higher stability and biocompatibility of PEDOT:PSS/[email protected]


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