Modified Graphite Electrode Research Articles

Catalytic Properties of Free-Base Porphyrin Modified Graphite Electrodes for Electrochemical Water Splitting in Alkaline Medium

Hydrogen generation via electrochemical water splitting is considered an eco-friendly pathway for obtaining this desired alternative energy source, and it has triggered an intensive search for low cost and efficient catalysts. Within this context, four free-base porphyrins were studied as heterogeneous catalysts for the oxygen and hydrogen evolution reactions (OER and HER) in alkaline aqueous solutions. TEM and STEM analyses of samples obtained by drop-casting the porphyrins from different organic solvents on TEM grids revealed a rich variety of aggregates due to the self-assembling property of the porphyrin molecules. Modified electrodes were manufactured by applying the four tetrapyrrolic macrocycles from various solvents on the surface of graphite supports, in one or more layers. Experiments performed in 0.1 M and 1 M KOH electrolyte solutions allowed the identification of the most electrocatalytically active electrodes for the OER and HER, respectively. In the first case, the electrode was manufactured by applying three layers of 5-(4-pyridyl)-10,15,20-tris(4-phenoxyphenyl)porphyrin on the graphite substrate from N,N-dimethylformamide solution was identified as overall catalytically superior. In the second case, the electrode obtained by applying one layer of 5,10,15,20-tetrakis(4-allyloxyphenyl)-porphyrin from benzonitrile solution displayed an HER overpotential value of 500 mV at i = −10 mA/cm2 and a Tafel slope of 190 mV/dec.

Investigation on a Self-Breakdown Repetitive Gap Switch Based on the Graphite Electrodes With TiC Surface Modification

In this article, a self-breakdown repetitive gap switch based on the graphite electrodes with surface modified by TiC is investigated to improve the scattering of the breakdown voltage. The self-breakdown repetitive gap switch was experimentally studied with the graphite electrodes and two kinds of TiC modified graphite electrodes (hereinafter referred to as TiC-I electrodes and TiC-II electrodes). Results show that the scatterings of the breakdown voltages of the graphite, TiC-I and TiC-II electrodes were 2.49%, 1.80%, and 1.54%, respectively. Compared with the graphite electrodes, the mass losses of TiC-I and TiC-II electrodes are reduced by 50% and 68%. The influence of electrode surface morphology on the switch stability is analyzed based on the mechanism of switch conduction process. Compared with the graphite electrodes, the electric field amplification coefficients of TiC-I and TiC-II electrodes are more evenly distributed, which leads to the more evenly distributed field emission current density. Thus, the breakdown areas of TiC-I and TiC-II electrodes are smaller and the gas breakdown processes are more stable than those of the graphite electrodes, resulting in smaller scattering of the breakdown voltage. The method that decreases the scattering of the breakdown voltage and reduces the mass loss of the electrodes by modifying graphite electrodes surface can greatly improve the stability of the switch, which is of significance to the application of the switch in the compact, long time stable operation of high-power pulse power devices.

Simultaneous electro-determination of trace copper, lead, and cadmium in tap water by using silver nanoparticles and graphene nanoplates as nanocomposite modified graphite electrode

This study provides a sensitive platform based on silver nanoparticles/graphene nanoplates modified graphite electrode (AgNPs/GrNPs/GE) for the simultaneous and selective voltammetric determination of heavy metal ions in tap water, including such Cd (II), Cu (II), and Pb (II). The as-prepared graphite electrodes were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and field emission scanning electron microscopy (FESEM) experiments. Furthermore, square wave anodic stripping voltammetry (SWASV) was performed to determine the cations mentioned above on the AgNPs/GrNPs/GE surface. Moreover, experimental parameters affecting the simultaneous determination of target metal ions were thoroughly tuned and optimized. When the suggested electrochemical sensor was performed under optimal conditions, detection limits of 5.0, 4.1, and 1.0 ng L−1 were obtained for Cd (II), Cu (II), and Pb (II), respectively. The electrode could also detect Zn (II) and Hg (II), around −1.13 and +0.05 V, respectively. The results revealed that the developed electrochemical sensor has high practical applicability, reproducibility and stability in detecting heavy metal ions.

Graphene oxide/gold nanoparticle/graphite fiber microelectrodes for directing electron transfer of glucose oxidase and glucose detection

A promising electrochemical sensor is investigated using graphene oxide (GO)/gold nanoparticle (AuNP)-modified graphite electrodes to enhance charge transport in electrochemical biosensors and increase the sensitivity for glucose detection. An efficient charge transfer pathway is formed by interconnected GO nanosheets and AuNP along the graphite fiber (GF) electrode (GFE). The positive GO can adsorb glucose oxidase (GOD) by electrostatic attraction. The detected response current of the sensor is linearly related to the glucose concentration within a detection limit of 1.2 μM. Furthermore, this glucose sensor has high stability, good reproducibility and excellent selectivity for various oxidizable molecules such as dopamine (DA), uric acid (UA), ascorbic acid (AA) and other molecules causing chaff interference (fructose, lactose and galactose). It is worth noting that this work shows a new method using covalent bonds and self-assembly on the surface of GF for fabricating excellent electrochemical glucose biosensors.

A comparative study on NiO nanocrystal modified graphite and Au electrode matrices as immobilization supports for laccase enzyme in amperometric biosensing for catechol detection

A comparative study of the electrochemical behaviours of two different electrode matrices used in the construction of amperometric laccase biosensors is reported here for catechol detection in water. The matrices considered are NiO nanocrystal (NC) modified graphite electrode (MCPE-NiO) and Au electrode of Clark type DO sensor. The laccase enzyme from Trametes versicolour was immobilized on electrode surfaces by co-crosslinking method using bovine serum albumin, a protein-based stabilizer, along with glutaraldehyde as the crosslinking agent. A comparison of the stability parameters of the electrode designs was carried out including sensitivity, calibration plots, analytical data and storage stability, and the biosensor performance was shown to be superior for MCPE-NiO-Lac compared to Au-Lac electrode. The NC modified system reached steady state within 6 seconds after the analyte contact and displayed a lower detection limit of 0.95 μM, while the Au electrode took 3 minutes to reach the same and had lower detection limit of 4 μM. Better reproducibility and longer linear response was also observed for MCPE-NiO system compared to the latter, all of which could be attributed to the microstructure of the electrode and the surface lattice arrangement in the embedded nanocrystals. Copyright © 2018 VBRI Press.

Electrochemical glucose biosensor based on biosynthesized silver nanoparticles and polyvinylpyrolidone modified graphite electrode

In the present work, we have biosynthesized silver nanoparticles (AgNPs) using leaf extract of Euphorbia geniculata and successfully deposited them onto the polyvinyl pyrolidone (PVP) modified graphite electrode (Gr/PVP). The resulting electrode is used as a matrix for the immobilization of glucose oxidase (GOx) enzyme. The immobilized electrode (Gr/PVP/AgNPs/GOx) is characterized by scanning electron microscopy and its performance is evaluated and optimized using cyclic voltammetry and differential pulsevoltammetrictechniques. Under neutral pH conditions, at room temperature, the developed Gr/PVP/AgNPs/GOx sensor showed excellent electrocatalytic activity towards the oxidation of glucose. Further, it is used for the determination of glucose in the concentration range of 0.1-7 mM with a detection limit of 0.15 µM and sensitivity of 29.72 µA mM-1 cm-2. In addition, the response of GOx biosensor is found to be uninfluenced by some common possible interferents. The findings of present work are significant and imply potential applications for biosynthesized AgNPs as effective, non-toxic biocompatible sensor fabrication materials. Copyright © 2018 VBRI Press.

Peptide nanotube functionalized molecularly imprinted polydopamine based single-use sensor for impedimetric detection of malathion.

In the present study, a peptide nanotube functionalized polydopamine (p-Dop) based molecularly imprinted (MIP) sensor system was constructed, characterized, and studied for the impedimetric sensing of an organophosphorus pesticide, malathion (MLT). Electropolymerization in the presence of a template (MLT) was utilized as a convenient and effective strategy to generate imprinted p-Dop films on peptide nanotubes (PNTs) modified graphite electrodes (PGEs). Upon the removal of template, the adsorption of MLT on the specific cavities formed in the MIP film was tracked using electrochemical impedance spectroscopy (EIS). To attain optimal sensor response, experimental conditions, such as film thickness, analyte/functional monomer ratio, and desorption/adsorption time, were analyzed. The obtained MIP(p-Dop)-PNT-PGE sensor exhibited high sensitivity for electrochemical MLT analysis with a wide dynamic detection range of 13pgmL-1 - 1.3µgmL-1 and a LOD of 1.39pgmL-1. The combination of a bio-inspired p-Dop-based MIP with the EIS technique allowed excellent sensitivity and selectivity toward MLT sensing which also yielded high recoveries in real samples. The success of this research strategy in real samples revealed its potential for various future environmental applications.

In Situ Electrochemical Production of Metal‐organic Hybrid Composite Film from Nickel Containing Polyoxometalate and 3,4‐Ethylenedioxy‐thiophene for Sensor Application

AbstractIn situ electrochemical synthesis of an organic‐inorganic hybrid material composed of poly(3,4‐ethylenedioxythiophene) (PEDOT) and nickel‐based Keggin type polyoxometalate, K7[NiIIINiII(H2O)W11O39].15H2O(NiPOM), has been proposed here. The remarkable optical and electrical properties of the PEDOT and the unique redox properties of NiPOM have synergistically combined to make the hybrid structure highly desired multi‐functional materials for a myriad of applications. The driving force for the formation of hybrid structure is thought to be electrostatic interactions between POM anions and cationic polaron/bipolaron structures that in the PEDOT. PEDOT/NiPOM based hybrid composite modified graphite electrode has been used for non‐enzymatic glucose sensor platform as a sample of applications. Furthermore, PEDOT/NiPOM based sensor platform was successfully utilized for detection of glucose content with the lowest detection limit in real samples like honey and milk. These results suggest that PEDOT/NiPOM metal‐organic hybrid composite could be utilized as multi‐functional material for a myriad of applications.

Low Cost Paper-based Electrochemical Sensing Platform for the Determination of Hydrogen Peroxide

A rapid, precise, low cost, selective and sensitive paper-based electrochemical device for the determination of H2O2 in milk is described here. Commercially available varnish and a simple hand drawing method were used to develop the hydrophobic pattern to generate a hydrophilic detection zone on the filter paper. The electrode system was fabricated on the detection zone in order to detect H2O2 electrochemically. A commercially available graphite pencil and conductive silver ink were used to fabricate the counter electrode and pseudo-reference electrode, respectively. A paste of Prussian blue (PB) modified graphite, unmodified graphite and phenol-formaldehyde polymer were used to fabricate a PB modified graphite working electrode on paper. This modified electrode showed electrocatalytic activity towards the reduction of H2O2 and it was successfully used for the chronoamperometric detection of H2O2 at 0 V vs Ag reference electrode in 0.1 mol l-1 phosphate buffer, buffered at pH 6.0 in 0.1 mol l-1 KCl. Under optimum conditions, the calibration curve for the H2O2 determination was linear from 5 to 50 mmol l-1 with a detection limit (LoD = x ̅ + 3SD) of 4.0 mmol l-1. In addition, the PB modified graphite electrode showed selectivity for H2O2 detection in the presence of ascorbic acid, sucrose and citric acid.

Fabrication of reduced graphene oxide/ruthenium oxide modified graphite electrode for voltammetric determination of tryptophan

Fabrication of reduced graphene oxide/ruthenium oxide modified graphite electrode for voltammetric determination of tryptophan

A Simple Nano Cerium Oxide Modified Graphite Electrode for Electrochemical Detection of Formaldehyde in Mushroom

In this present work, electrochemical detection and quantification of formalin (FAL) trace present in mushroom (Agaricus bisporus) was premeditated using a cerium oxide nanoparticle modified graphite paste electrode (CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> @GP). Cerium oxide (CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) nanoparticles (nps) were synthesized through the sol-gel technique from cerium nitrate hexahydrate using poly (ethylene glycol) as a capping agent. The prepared CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nps were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques which revealed the successful formation of the cubic phase of CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> having crystallite size 4.84 nm. The prepared CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nps were used to modify the graphite paste electrode (bare GP). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques were utilized to study comparative electroanalytical features of the fabricated electrodes. Under optimized experimental conditions, CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> @GP exhibited a wide linear range from 25 μM-1mM and a limit of detection of 1 μM. Moreover, CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> @GP featured high repeatability, reproducibility, and long-term stability. The electrode exhibited high selectivity for FAL in the presence of interferences like ethanol, methanol, formic acid, benzaldehyde, and acetone. CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> @GP demonstrated exceptional aptitudes in electrochemical behavior when subjected to mushroom extract.

Electrochemical detector based on a modified graphite electrode with phthalocyanine for the elemental analysis of actinides

The quantification of actinides in aqueous solutions involves complex and expensive separation processes. Electrochemical methods have been widely used for the quick and accurate identification and quantification of organic and inorganic compounds directly or indirectly. Therefore, this work proposes the use of modified graphite with phthalocyanine for electrochemical detection and quantification of Th, U, Pu, Am, and Cm, in aqueous media by cyclic voltammetry. The electrodes were characterized by Raman and infrared spectroscopy, and the cyclic voltammetry data were modeled with Aoki’s model. The detection limits (DL) and the quantification limits (QL) reached by the electrochemical detection of these actinides were of the order of ppt. Aoki’s model fitted perfectly with the experimental data. The functionalization of graphite electrodes promotes the formation of phthalic anhydride, and the phthalocyanine is anchored on the epoxy groups of the graphite. The electrochemical detection process of these actinides is indirect. This electrochemical detector is cheap and disposable and can be an alternative for an initial characterization of actinides in liquid waste.

Investigation of electrocatalytic activity of NiTPPBr6 on the graphite electrode for oxidation of methanol, ethanol, 1-propanol and 2-propanol

Due to the importance of producing clean energy through systems such as alcoholic fuel cell, methanol, ethanol, 1-propanol, and 2-propanol, these alcohols were oxidized at the modified graphite electrode by NiTPPBr6 / NiTPPBr8 as a clean electrocatalyst in an alkaline media. This process investigated by various techniques such as cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS), in all cases showed Cottrell type behavior with the diffusion of coefficients of 2.04 × 10[Formula: see text], 1.3 × 10[Formula: see text] 8.3 × 10[Formula: see text] cm[Formula: see text] s[Formula: see text] for the corresponding alcohols respectively. Likewise, the catalytic rate constant for methanol oxidation was found to be 2.9 × 108 cm3mol[Formula: see text] s[Formula: see text] through chronoamperometric measurements. Interestingly, the order in activity for oxidation of the alcohols introduced with the electrocatalyst was: 2-propanol [Formula: see text] 1-propanol [Formula: see text] ethanol [Formula: see text] methanol and was unlike previous studies in which the oxidation current was reduced by increasing the number of carbon atoms from methanol to propanol.

Yeast-based microbial biofuel cell mediated by 9,10-phenantrenequinone

Microbial fuel cells can be efficiently used for simultaneous cleaning of wastewater and generation of electricity. This research demonstrates the applicability of Baker yeast cells in the design of microbial biofuel cells. The applicability the 9,10-phenantrenequinone (PQ) as a redox mediator in the design of yeast-based microbial cell (MFC) for the improvement of charge transfer through the yeast cell membrane and cell wall towards the electrode was evaluated. The viability of bakers' yeast and pure Saccharomyces cerevisiae cell strains was investigated by evaluating the growth velocity of cells in the presence of a different concentration of PQ in solution. The growth curves of bakers' yeast showed that they were more resistant to PQ. Electrochemical measurements were performed with PQ as a redox mediator, which was (i) dissolved in solution and (ii) adsorbed on a graphite electrode. Differently modified graphite electrodes (namely: (i) non-modified, (ii) yeast-modified, (iii) modified by PQ and yeast) were evaluated. The modified electrodes were evaluated as anodes of MFC. The dependence of potential on external resistance and generated power of MFC was evaluated. Maximal open circuit potential was 178 mV at 7.8 mM of glucose and 23 mM of potassium ferricyanide. Maximal power of BFC calculated at the same conditions was registered at 56 mV, and it reached 22.2 mW/m2 (at 30 mM of glucose). The application of PQ as a redox mediator for yeast-based MFC improves electron transfer through the yeast cell membrane and cell wall towards electrode without any noticeable decrease of yeast cell viability.

Simultaneous Electro-Determination of Trace Copper, Lead and Cadmium in Tab Water by Using Silver Nanoparticles and Graphene Nanoplates as Nanocomposite Modified Graphite Electrode

Simultaneous Electro-Determination of Trace Copper, Lead and Cadmium in Tab Water by Using Silver Nanoparticles and Graphene Nanoplates as Nanocomposite Modified Graphite Electrode

Reduced graphene oxide coated graphite electrodes for treating Reactive Turquoise Blue 21 rinse water using an indirect electro-oxidation process

The present study deals with the decolourization of synthetic Reactive Turquoise Blue 21 (RTB21) dye-based model wastewater using an indirect electro-oxidation process and enhanced by modified graphite electrodes. Graphene oxide (GO) was successfully synthesized and deposited on the surface of pre-treated graphite electrodes. It was further reduced to form reduced graphene oxide (rGO). The resultant newly developed anode electrodes were designated as (Gr)0, (rGO/Gr)1, and (rGO/Gr)2 and used for the treatment of wastewater. Electrodes, thus developed, were characterized using Fourier-transform infrared spectroscopy, X-ray diffractions, Field emission scanning electron microscopy, and Contact angle (CA). The effect of process parameters such as initial pH, current density, electrolyte concentration, and temperature on the performance of novel anode electrodes was investigated. The colour removal efficiency was increased significantly almost 25.80% in the presence of a modified electrode with the highest efficiencies of about 96.69% in a natural pH environment, 200 A/m2, 2 g/L NaCl concentration, 30 °C temperature, and 15 min process time for 50 ppm RTB21 dye concentration for (rGO/Gr)2 electrode. The RTB21 decolourization by indirect electro-oxidation process follows the pseudo-first-order kinetics, and the activation energy was estimated to be 23.42 kJ/mol. The stability of (rGO/Gr)2 electrode was also examined. The rGO coated electrode was a superior electrode for the indirect electro-oxidation process, giving enhanced colour removal (%).

Electrochemical sensor for determination of nitrobenzene in aqueous solution based on nanostructures of TiO2/GO

We synthesized polymer nanocomposites (PNCs) based on nanostructures of flower-like hierarchical rutile-phase TiO2 nanorod microspheres that were grow on oxide graphene sheets (GO). The synthesis parameters were modified to obtain desired morphologies (flower-like and cauliflower). The two PNC of TiO2/GO were characterized by scanning and transmission electron microscopy, dispersive energy spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, thermal gravimetric analysis (TGA), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The modified graphite electrodes with TiO2/GO were evaluated as an electrochemical sensor in the determination of nitrobenzene (NB) using CV. The physicochemical characterization techniques confirmed the growth of the rutile-phase TiO2 nanoarchitecture on the GO sheets surface. The sensitivity and the detection interval of the sensor increase with the increasing amount of GO, reaching concentrations of the parts per billion. The TiO2/GO sensors shows an acceptable repeatability, reproducibility and stability in the detection of nitrobenzene (NB), and the recovery results in synthetic wastewater samples are excellent.

Electroactive biofilms on surface functionalized anodes: The anode respiring behavior of a novel electroactive bacterium, Desulfuromonas acetexigens

Surface chemistry is known to influence the formation, composition, and electroactivity of electron-conducting biofilms. However, understanding of the evolution of microbial composition during biofilm development and its impact on the electrochemical response is limited. Here we present voltammetric, microscopic and microbial community analysis of biofilms formed under fixed applied potential for modified graphite electrodes during early (90 h) and mature (340 h) growth phases. Electrodes modified to introduce hydrophilic groups (-NH2, -COOH and -OH) enhance early-stage biofilm formation compared to unmodified or electrodes modified with hydrophobic groups (-C2H5). In addition, early-stage films formed on hydrophilic electrodes are dominated by the gram-negative sulfur-reducing bacterium Desulfuromonas acetexigens while Geobacter sp. dominates on -C2H5 and unmodified electrodes. As biofilms mature, current generation becomes similar, and D. acetexigens dominates in all biofilms irrespective of surface chemistry. Electrochemistry of pure culture D. acetexigens biofilms reveal that this microbe is capable of forming electroactive biofilms producing considerable current density of > 9 A/m2 in a short period of potential-induced growth (~19 h following inoculation) using acetate as an electron donor. The inability of D. acetexigens biofilms to use H2 as a sole source electron donor for current generation shows promise for maximizing H2 recovery in single-chambered microbial electrolysis cell systems treating wastewaters.

Direct Electrochemistry and Sensitive Detection of Guanosine on Nanopolymeric Surfaces Bearing Boronic Acid Groups

AbstractThis paper describes the use of novel boronic acid containing polymeric surfaces for following improved direct electrochemistry and highly sensitive and selective electrochemical detection of guanosine. Effective and robost boronic acid containing electroactive polymeric layers based on poly(3‐aminophenylboronic acid) (PAPBA) in the existence of a convenient nanomaterial (multi‐walled carbon nanotubes, MWCNTs) were fabricated onto graphite surfaces with a simple and reproducible single‐step electro‐fabrication method for the first time. So‐formed electrodes were then utilized for direct electrochemistry of guanosine and determination of guanosine. The electrode presented a linearity to guanosine from 1 μM to 120 μM and the detection limit was calculated as 0.14 μM (n=3). It was feasible to differentiate guanine and guanosine with a good peak separation value of 0.31 V. Furthermore, analytical performance of this novel electrode was compared with the performances of graphene added polymeric layer modified graphite electrode and unmodified graphite electrode.

Simple sonochemical synthesis of SrCuO2 assisted GCN nanocomposite for the sensitive electrochemical detection of 4-AAP

The present study demonstrates the development of an electrochemical sensor to detect and quantify 4- Aminoantipyrene (4-AAP), using strontium copper oxide (SrCuO2) microspheres and graphitic carbon nitride (GCN) as a composite in the modified graphite electrode. The SrCuO2 is synthesized by sonochemical method and GCN was prepared using pyrolysis method. Field emission scanning electron microscopy (FESEM), X-ray diffraction spectroscopy (XRD) techniques are used in the characterization of the synthesized materials. Subsequently, the well characterized GCN and SrCuO2 are deposited onto a graphite (Gr) surface and used as transducer material in the fabrication of the electrode. Electrochemical characterization of the as fabricated electrode was carried out with the help of electrochemical impedance spectroscopy (EIS). The results validated the conducting nature of SrCuO2 and GCN. In Comparison with the unmodified electrode, the proposed Gr/SrCuO2/GCN electrochemical sensor, displayed enhanced electrocatalytic behavior towards 4-AAP. The sensor's analytical performance is calibrated and evaluated by cyclic voltammetry (CV) and Differential pulse voltammetry (DPV). The sensor exhibited exceptional characteristics like wide linear range, low detection limit. In addition, the proposed sensor also showed an excellent repeatability, good reproducibility and superior stability. Finally, the real sample analysis results indicated an acceptable recovery range that endeavored the use of the proposed sensor to monitor 4-AAP.