Showing papers on "Cyclic voltammetry published in 2021"

Absence of CO2 electroreduction on copper, gold and silver electrodes without metal cations in solution

Abstract: The electrocatalytic reduction of carbon dioxide is widely studied for the sustainable production of fuels and chemicals. Metal ions in the electrolyte influence the reaction performance, although their main role is under discussion. Here we studied CO2 reduction on gold electrodes through cyclic voltammetry and showed that, without a metal cation, the reaction does not take place in a pure 1 mM H2SO4 electrolyte. We further investigated the CO2 reduction with and without metal cations in solution using scanning electrochemical microscopy in the surface-generation tip-collection mode with a platinum ultramicroelectrode as a CO and H2 sensor. CO is only produced on gold, silver or copper if a metal cation is added to the electrolyte. Density functional theory simulations confirmed that partially desolvated metal cations stabilize the CO2– intermediate via a short-range electrostatic interaction, which enables its reduction. Overall, our results redefine the reaction mechanism and provide definitive evidence that positively charged species from the electrolyte are key to stabilize the crucial reaction intermediate.

Understanding and Calibration of Charge Storage Mechanism in Cyclic Voltammetry Curves

Abstract: Noticeable pseudo-capacitance behavior out of charge storage mechanism (CSM) has attracted intensive studies because it can provide both high energy density and large output power. Although cyclic voltammetry is recognized as the feasible electrochemical technique to determine it quantitatively in the previous works, the results are inferior due to uncertainty in the definitions and application conditions. Herein, three successive treatments, including de-polarization, de-residual and de-background, as well as a non-linear fitting algorithm are employed for the first time to calibrate the different CSM contribution of three typical cathode materials, LiFePO4 , LiMn2 O4 and Na4 Fe3 (PO4 )2 P2 O7 , and achieve well-separated physical capacitance, pseudo-capacitance and diffusive contributions to the total capacity. This work can eliminate misunderstanding concepts and correct ambiguous results of the pseudo-capacitance contribution and recognize the essence of CSM in electrode materials.

Sub-Thick Electrodes with Enhanced Transport Kinetics via In Situ Epitaxial Heterogeneous Interfaces for High Areal-Capacity Lithium Ion Batteries.

Abstract: The ever-growing portable electronics and electric vehicle draws the attention of scaling up of energy storage systems with high areal-capacity The concept of thick electrode designs has been used to improve the active mass loading toward achieving high overall energy density However, the poor rate capabilities of electrode material owing to increasing electrode thickness significantly affect the rapid transportation of ionic and electron diffusion kinetics Herein, a new concept named "sub-thick electrodes" is successfully introduced to mitigate the Li-ion storage performance of electrodes This is achieved by using commercial nickel foam (NF) to develop a monolithic 3D with rich in situ heterogeneous interfaces anode (Cu3 P-Ni2 P-NiO, denoted NF-CNNOP) to reinforce the adhesive force of the active materials on NF as well as contribute additional capacity to the electrode The as-prepared NF-CNNOP electrode displays high reversible and rate areal capacities of 681 and 150 mAh cm-2 at 040 and 60 mA cm-2 , respectively The enhanced Li-ion storage capability is attributed to the in situ interfacial engineering within the NiO, Ni2 P, and Cu3 P and the 3D consecutive electron conductive network In addition, cyclic voltammetry, charge-discharge curves, and symmetric cell electrochemical impedance spectroscopy consistently reveal improved pseudocapacitance with enhanced transports kinetics in this sub-thick electrodes

A novel electrochemical aflatoxin B1 immunosensor based on gold nanoparticle-decorated porous graphene nanoribbon and Ag nanocube-incorporated MoS2 nanosheets

Abstract: The accurate and precisive monitoring of aflatoxin B1 (AFB1), which is one of the most hazardous mycotoxins, especially in agricultural products, is significant for human and environmental health. AFB1 generally contaminates agricultural products such as corn and feedstuff. In this paper, a novel electrochemical AFB1 immunosensor was constructed based on Ag nanocubes (AgNCs) incorporated trigonal metallic MoS2 nanosheets with 1T phase (AgNCs/1T-MoS2) as signal amplification and gold nanoparticles/porous graphene nanoribbon (AuNPs/PGNR) as an electrochemical sensor platform. First, the chronoamperometry method was implemented to provide electrodeposition of AuNPs on PGNR following chemical reduction of PGNR. Immobilization of the primer AFB1 antibody was performed via amino-gold affinity between primer antibody and AuNPs/PGNR composite. Subsequently, the conjugation of seconder antibody to AgNCs/1T-MoS2 was performed by strong π–π and electrostatic interactions. To describe the surface morphology and elemental composition of the prepared electrochemical AFB1 immunosensor, physicochemical characterization techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were used. Furthermore, cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) techniques were used to evaluate the immunosensor's electrochemical performance. The developed electrochemical AFB1 immunosensor offered a good sensitivity with a detection limit (LOD) of 2.00 fg mL−1. Finally, an electrochemical AFB1 immunosensor with satisfactory selectivity, stability and reusability was applied in wheat samples with high recovery.

Preparation of different heteroatom doped graphene oxide based electrodes by electrochemical method and their supercapacitor applications

Abstract: In this study, one-step preparation method of different heteroatom (-S, -N, -Cl) doped graphene oxide electrodes were achieved as electrode materials for the purpose of high-capacity supercapacitors Microscopic, spectroscopic, and electrochemical methods were used to characterize the prepared electrodes Formation of -ClO2, -ClO3, -SOx (x:2, 3) and -NO2 groups on the graphene oxide-based electrodes were determined by X-ray photoelectron spectroscopy analysis Detail reaction mechanisms were suggested for the formation of these groups on the electrode surface for the first time in the literature Different surface properties of graphene oxide structures in the electrodes were investigated by scanning electron microscopy and atomic force microscopy Electrochemical behaviors of the prepared electrodes were characterized by cyclic voltammetry and electrochemical impedance spectroscopy Sulphur, nitrogen, and chlorine doped graphene oxide electrodes were used as electrode materials for supercapacitor applications Since different heteroatom doped graphene oxide-based electrodes showed different capacitive behavior Areal capacitances of -S, -N and -Cl doped graphene oxide electrodes were determined as 2064 mFcm−2, 5332 mFcm−2 and 1098 mFcm−2, respectively with 10 mAcm−2

Electrochemical immunosensor development based on core-shell high-crystalline graphitic carbon nitride@carbon dots and Cd0.5Zn0.5S/d-Ti3C2Tx MXene composite for heart-type fatty acid–binding protein detection

Abstract: Acute myocardial infarction (AMI) is a significant health problem owing to its high mortality rate. Heart-type fatty acid–binding protein (h-FABP) is an important biomarker in the diagnosis of AMI. In this work, an electrochemical h-FABP immunosensor was developed based on Cd0.5Zn0.5S/d-Ti3C2Tx MXene (MXene: Transition metal carbide or nitride) composite as signal amplificator and core-shell high-crystalline graphitic carbon nitride@carbon dots (hc-g-C3N4@CDs) as electrochemical sensor platform. Firstly, a facile calcination technique was applied to the preparation of hc-g-C3N4@CDs and immobilization of primary antibody was performed on hc-g-C3N4@CDs surface. Then, the conjugation of the second antibody to Cd0.5Zn0.5S/d-Ti3C2Tx MXene was carried out by strong π-π and electrostatic interactions. The prepared electrochemical h-FABP immunosensor was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD) method, Fourier-transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The prepared electrochemical h-FABP immunosensor indicated a good sensitivity with detection limit (LOD) of 3.30 fg mL−1 in the potential range +0.1 to +0.5 V. Lastly, low-cost, satisfactory stable, and environmentally friendly immunosensor was presented for the diagnosis of acute myocardial infarction.

High performance of screen-printed graphite electrode modified with Ni–Mo-MOF for voltammetric determination of amaranth

Abstract: The present study introduces a novel Ni–Mo-MOF-modified screen printed electrode (Ni–Mo-MOF/SPE) to sensitively and rapidly detect amaranth. Cyclic voltammetry (CV) was also applied to evaluate the electrochemical behavior of amaranth on the surfaces of bare SPE and Ni–Mo-MOF/SPE, and differential pulse voltammetry (DPV) to calculate linearly detection range of amaranth. According to the results, various linear oxidation peak currents were obtained at different concentrations (between 0.15 ± 0.001 and 500.0 ± 0.001 µM) and the limit of detection (LOD) was estimated to be 0.05 ± 0.001 µM in the optimal conditions. Additionally, the efficacy of developed electrode was tested by real samples, the results of which were satisfactory. The proposed Ni–Mo-MOF/SPE not only had special properties such as high selectivity, high sensitivity, cost-effectiveness and rapid response, but also was shown to possess wide applications for sensitively amaranth detection in real samples.

Photocatalytic hydrogen generation via water splitting using ZIF-67 derived Co3O4@C/TiO2

Abstract: Water splitting via photocatalysis using titanium dioxide (TiO2) holds great potential for hydrogen gas generation. Herein, zeolitic imidazolate framework (ZIF-67) was used as a sacrificial precursor for the synthesis of cobalt oxide embedded nitrogen doped carbon (Co3O4@C) that was used as a co-catalyst with TiO2 for the hydrogen generation via photocatalytic water splitting. The optimal loading of Co3O4@C (7 wt%) exhibited a photocatalytic hydrogen production rate (HGR) of 11,400 µmol g−1 h−1. It demonstrated a 75-fold and 110-fold increase for cumulative (5 h) and initial hydrogen generation rates, respectively. The electrochemical measurements such as cyclic voltammetry (CV), linear scan voltammetry (LSV), electrochemical independence spectroscopy (EIS) using Nyquist plots, and photocurrent response were conducted to evaluate the catalytic performance of Co3O4@C/TiO2. Transient photocurrent response showed significant enhancement (4-fold) in photocurrent density of TiO2. Co3O4@C promoted the photocatalytic performance of TiO2 and improved the HGR. The photocatalysis using Co3O4@C/TiO2 is recyclable for more than four cycles without significant loss of their performance. The results of our study may open the door for further exploration toward effective photocatalyst.

A polypyrrole/GO/ZnO nanocomposite modified pencil graphite electrode for the determination of andrographolide in aqueous samples

Abstract: This paper presents a novel electrochemical sensor based on a pencil graphite electrode (PGE) modified with molecularly imprinted graphene oxide/zinc oxide nanocomposites for a sensitive detection of andrographolide. This is the first report of the novel method of electroanalytical determination of andrographolide through a modified PGE. The modified PGE was successfully fabricated and characterized. Then, quantitative analyses were performed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The optimum conditions for this analysis were the supporting electrolyte containing 0.1 M KCl and 0.001 M K3Fe(CN)6, citrate buffer of pH 4, modulation amplitude of 50 mV, and scan rate of 10 mV/s. Under optimized parameters, a good linear response was obtained for andrographolide detection by DPV with a range of 50–145 µM and a detection limit of 42.6 µM. The relative standard deviation (R.S.D.) of the three measurements is 1.47%, which shows the excellent repeatability of the proposed method, while reproducibility analysis produced a R.S.D. value of 4.46%. The proposed technique with optimum conditions exhibited good selectivity towards the detection of andrographolide in the presence of ascorbic acid, uric acid, and cyclodextrin. This method was successfully applied to determine andrographolide in real water samples, and the results are comparable with the established method.

Preparation of Fe-SnO2@CeO2 nanocomposite electrode for asymmetric supercapacitor device performance analysis

Abstract: In this work, we report enhanced specific capactance and cycle stability of Fe-SnO2@CeO2 electrode for supercapacitor applications. The Fe-SnO2@CeO2 nanocomposite was synthesized through a simple chemical co-precipitation method. The electrochemical performances of the Fe-SnO2@CeO2 nanocomposite electrode are assessed by using cyclic voltammetry, galvanostatic charge/discharge and impedance spectroscopy techniques. In three electrode system, the Fe-SnO2@CeO2 nanocomposite electrode is exhibited a maximum specific capacitance of 348 F/g at a current density of 1 A/g. Further, the asymmetric supercapacitor (ASC) device performance has been evaluated and the ASC device produces a specific energy and specific power of 32.2 W h kg−1 and 747 W kg−1 at a current density of 1A/g, respectively. The device exhibited the capacitance retention of 85.05 % over 5000 cycles of operation. This study confirms that the Fe-SnO2@CeO2 is an alternative electrode material for high energy storage supercapacitor applications.

Functional Co3O4 nanostructure-based electrochemical sensor for direct determination of ascorbic acid in pharmaceutical samples

Abstract: Ionic liquid (IL)-assisted Co3O4 nanostructures were synthesized by a simple, facile and novel low-temperature aqueous chemical growth method and used for the modification of glassy carbon electrode (GCE) for the selective determination of ascorbic acid (AA). Different volumes of IL were used in the preparation of nanostructures to examine the effect of IL on the morphology and electrochemical performance of the synthesized material. The functionalities of the prepared material were investigated by FTIR, while the crystalline nature and phase purity of the material were confirmed by XRD results. FESEM analysis were carried out to expose the surface characteristics of the prepared nanostructures and the results demonstrated that the cobalt oxide nanostructures possess nanorods like morphology. The EDX results verified the maximum elemental percent composition for the cobalt and oxygen in the synthesized material. The electrochemical performance of Co3O4 nanostructures modified GCE was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical results demonstrated that the modified electrode shown outstanding performance in the determination of AA with a very low limit of detection (1 µM) along with higher stability and repeatability features. The novel AA sensor manifested exceptional sensitivity and selectivity over a wide linear range of concentration from 0.05 to 3 mM with the coefficient of determination R2 = 0.998. The applicability of the developed sensor was examined in the pharmaceutical samples that contain AA and the sensor selectively detected the AA from multiple ingredients that were present in their formulation with acceptable recovery. It describes the synthesis of [BMIM][PF6] IL functionalized cobalt oxide nanostructures through low-temperature aqueous chemical growth method and the synthesized material was utilized to fabricate an electrochemical sensor (Co3O4/GCE) for the selective determination of Ascorbic acid.

Electrochemical fabrication and supercapacitor performances of metallo phthalocyanine/functionalized-multiwalled carbon nanotube/polyaniline modified hybrid electrode materials

Abstract: In this work, we aimed to prepare three different metallo phthalocyanine/functionalized-multiwalled carbon nanotube/polyaniline/pencil graphite electrode (MPc/f-MWCNT/PANI/PGE) modified electrodes with high specific capacitance, high energy and power densities, and long cycle life for supercapacitors. In this concept, ZnPc/f-MWCNT/PANI/PGE, CuPc/f-MWCNT/PANI/PGE, and NiPc/f-MWCNT/PANI/PGE electrode materials were prepared by electrochemical method. The surface and structural properties of the prepared electrodes were investigated with Fourier-transform infrared spectroscopy (FT-IR), Scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDS), Atomic force microscope (AFM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area and electrical conductivity analyses. The electrochemical properties of these electrode materials were examined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge (GCD) analyses. The effects of preparation parameters and composite composition of the electrodes on electrochemical performance were investigated. The NiPc/f-MWCNT/PANI/PGE electrode has higher specific capacitance (325 F/g) than ZnPc/f-MWCNT/PANI/PGE (278 F/g), CuPc/f-MWCNT/PANI/PGE (282 F/g), f-MWCNT/PANI/PGE (162 F/g), and PANI/PGE (126 F/g) electrodes. In addition, all MPc/f-MWCNT/PANI/PGE electrodes have long-cycle life and maintained approximately 100% of its capacitance after 1000 charge-discharge cycles. As a result, the prepared MPc/f-MWCNT/PANI/PGE electrodes significantly removed the disadvantages of the components, and the synergistic effects between the components considerably improved supercapacitor performance of the electrodes.

Conversion of wheat husk to high surface area activated carbon for energy storage in high-performance supercapacitors

Abstract: Conversion of carbon-containing biomass into useful carbon products is highly demanded. A rising understanding of environmental problems explains the growing focus on evaluating bioproducts and wastes in numerous applications. Herein, the wheat husks derived activated carbon (WHAC) was employed as electrode material for supercapacitors' energy storage. Three samples of activated carbon were made using wheat husks, which were activated at different temperatures. The prepared electrodes were characterized and electrochemically tested using Fourier-transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscope, cyclic voltammetry, galvanostatic charge-discharge, and electrical impedance spectroscopy. The maximum capacitance (271.5 F g−1 at a current density of 0.5 A g−1) was observed for AC-800, activated at 800 °C. The electrochemical impedance showed low resistance (3.659 Ω) and low-frequency response (6.84 s). The AC-800 electrode exhibited the capacitance retention of 82% after 5000 cycles. The excellent electrochemical properties reveal the utilization of biomass waste as a potential electrode material for supercapacitors. The process used is simple, environmentally friendly, and could significantly reduce the county's biomass wastes from wheat husks. The approach can not only reduce environmental pollution but develop porous carbon electrodes for energy storage devices.

A Robust PtNi Nanoframe/N-Doped Graphene Aerogel Electrocatalyst with Both High Activity and Stability.

Abstract: Insufficient catalytic activity and stability, and high cost are the key barriers for Pt-based electrocatalysts in wide practical applications Herein, a hierarchically porous PtNi nanoframe/N-doped graphene aerogel (PtNiNF-NGA) electrocatalyst with outstanding performance toward methanol oxidation reaction (MOR) in acid electrolyte has been developed via a facile tert-butanol-assisted structure reconfiguration strategy The ensemble of the high-alloying-degree-modulated electronic structure and correspondingly the optimum MOR reaction pathway, the structure superiorities of hierarchical porosity, thin edges, Pt-rich corners, and the anchoring effect of the NGA, endow the PtNiNF-NGA with both prominent electrocatalytic activity and stability The mass and specific activity (1647 mA/mgPt , 38 mA/cm2 ) of the PtNiNF-NGA are 58 and 78 times higher than those of commercial Pt/C, respectively Especially, it exhibits exceptional stability under a 5-hour chronoamperometry test and 2200-cycle cyclic voltammetry scanning This work is of high inspiration for the design of Pt-based electrocatalysts with both high activity and stability