Improvement Of Electrochemical Activity Research Articles

Flexible electrochemical sensor based on a ZnO-doped SnO2 heterojunction for simultaneous electrochemical determination of p-aminophenol and acetaminophen

In this work, a novel flexible electrochemical sensor was successfully developed for the simultaneous determination of p-aminophenol and acetaminophen. The sensor is composed of a methanesulfonic acid-treated poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) film on a poly(ethylene terephthalate) substrate, which has been modified using a zinc oxide-doped tin oxide heterojunction applied through drop-coating (C-ZnO/SnO2-PEDOT/PET). The oxygen vacancies resulting from zinc oxide-doped tin oxide heterojunctions within highly conductive metal oxide nanomaterials enhance mass transfer and synergize seamlessly with methanesulfonic acid-treated electrically conductive dielectric PEDOT/PET films, leading to a substantial improvement in electrochemical activity. Under the optimal conditions, a wider linear range and lower detection limits were shown for p-aminophenol (2–511 μM, LOD=0.437 μM) and acetaminophen (2–591 μM, LOD=0.562 μM). In addition, the sensors demonstrated high accuracy in detecting p-aminophenol and acetaminophen in real samples, with recoveries of 99.36 %-99.60 % and 97.56 %-99.80 %, respectively. Furthermore, the flexible sensors maintained a superior electrochemical response when detecting p-aminophenol and acetaminophen at different bending angles, with relative standard deviations of 0.62 % and 1.68 %, respectively. These findings suggest potential applications for the development of wearable sensors in the future.

Improvement physical and photoelectrochemical properties of TiO2 nanorods toward biosensor and optoelectronic applications

In this study we examine effect of the solvent ratio on TiO2 physical and photoelectrochemical properties utilizing economical hydrothermal process. Sample properties were examined using XRD, SEM, Raman, UV–vis, PL, photocurrent, Mott–Schottky, and EIS measurements. XRD patterns revealed that TiO2 samples represent a polycrystalline nature with a Tetragonal structure. Peaks at 609, 144, and 443 cm−1 were observed in Raman spectra indicating the production of the TiO2 rutile phase. SEM images showed that TiO2 nanorods formed evenly with square top facets and a tetragonal form. UV–vis results displayed an optical absorption edge between 386 and 405 nm which is associated with the band gap of TiO2 NRs films. The generated TiO2 NRs films exhibit n-type semiconductor behavior according to the photocurrent measurements. Mott-Schottky experiments indicated that the donor density and flat band potential varied with decreased acid ratio from 1.55 × 1018 to 3.33 × 1018 cm−3 and-0.47 to-0.72 V, respectively. As observed by EIS, the resistivity to charge transfer declined, reaching its lowest level at 5:11 ml, indicating improvement of electrochemical activity and structural properties with decreasing the HCl concentration. Additionally, the fabricated TiO2 NRs films was employed as biosensor for glucose where a fast amperometric response and good operating stability were detected.

Electrochemical sensor for isoniazid detection by using a WS2/CNTs nanocomposite

This paper presents a new modified electrode that combines the high electrical conductivity of carbon nanotubes (CNTs) with the catalytic sites of WS2 (named WS2/CNTs) for isoniazid detection. Electrochemical and electroanalytical properties of the WS2/CNTs/glassy carbon electrode (GCE)-modified electrodes were investigated by cyclic voltammetry and differential pulse voltammetry (DPV). The composite material was characterized by Raman spectroscopy, X-ray diffractometry (XRD), and scanning electron microscopy . The electrochemical performance of the WS2/CNTs/GCE sensor exhibited a limit of detection of 0.24 μM with a linear range from 10 to 80 μM of isoniazid using DPV. This sensor provided enhanced stability and electrocatalytic activity for isoniazid oxidation reactions. Recoveries ranging from 96.9 to 104.5% were calculated, demonstrating satisfactory accuracy of the proposed method. The improvement of electrochemical activity was assigned to synergic effects obtained by combining the catalytic sites from WS2 and the known electrical conductivity and large surface area of the CNTs, resulting in an anticipation of the oxidation peak of isoniazid in about 400 mV in comparison with bare GCE.

Development of Ni-Sr(V,Ti)O3-δ Fuel Electrodes for Solid Oxide Fuel Cells.

A series of strontium titanates-vanadates (STVN) with nominal cation composition Sr1-xTi1-y-zVyNizO3-δ (x = 0–0.04, y = 0.20–0.40 and z = 0.02–0.12) were prepared by a solid-state reaction route in 10% H2–N2 atmosphere and characterized under reducing conditions as potential fuel electrode materials for solid oxide fuel cells. Detailed phase evolution studies using XRD and SEM/EDS demonstrated that firing at temperatures as high as 1200 °C is required to eliminate undesirable secondary phases. Under such conditions, nickel tends to segregate as a metallic phase and is unlikely to incorporate into the perovskite lattice. Ceramic samples sintered at 1500 °C exhibited temperature-activated electrical conductivity that showed a weak p(O2) dependence and increased with vanadium content, reaching a maximum of ~17 S/cm at 1000 °C. STVN ceramics showed moderate thermal expansion coefficients (12.5–14.3 ppm/K at 25–1100 °C) compatible with that of yttria-stabilized zirconia (8YSZ). Porous STVN electrodes on 8YSZ solid electrolytes were fabricated at 1100 °C and studied using electrochemical impedance spectroscopy at 700–900 °C in an atmosphere of diluted humidified H2 under zero DC conditions. As-prepared STVN electrodes demonstrated comparatively poor electrochemical performance, which was attributed to insufficient intrinsic electrocatalytic activity and agglomeration of metallic nickel during the high-temperature synthetic procedure. Incorporation of an oxygen-ion-conducting Ce0.9Gd0.1O2-δ phase (20–30 wt.%) and nano-sized Ni as electrocatalyst (≥1 wt.%) into the porous electrode structure via infiltration resulted in a substantial improvement in electrochemical activity and reduction of electrode polarization resistance by 6–8 times at 900 °C and ≥ one order of magnitude at 800 °C.

3D hybrids based on WS2/N, S co-doped reduced graphene oxide: Facile fabrication and superior performance in supercapacitors

To further enhance electrochemical performance of WS2-based materials in supercapacitors, a 3D architecture with WS2 nanoflakes interconnected and quantum dots anchored on N and S co-doped reduced graphene oxide (WS2/N,S-rGO) crumpled nanosheets is fabricated for the first time via a novel, facile and scalable approach, which is based on rapid solution combustion synthesis of the precursor and subsequent gas-solid phase sulfurization, and needs no such tedious processes as filtration, washing and drying. Significantly, the WS2/N,S-rGO hybrid possesses a specific capacitance of 1562.5 F g−1 at 1 A g−1 and a rate capability of 780 F g−1at 40 A g−1, which are superior to the currently-reported WS2-based electrode materials. As to the WS2/N,S-rGO hybrid, the 3D hierarchical architecture, synergistic effect between WS2 and N,S-rGO nanosheets as well as nitrogen and sulfur co-doping on rGO offer a variety of advantages such as larger contact surface area, shorter ion diffusion path, excellent charge transport and especially the enhanced pseudo-capacitance of rGO, and thus result in huge improvement in electrochemical activity, which demonstrate the WS2/N,S-rGO hybrid to be a superb anode material in supercapacitors.

Comparative investigation of electrochemically synthesized (α+β) layered nickel hydroxide with mixture of α-Ni(OH)2 and β-Ni(OH)2

Nickel hydroxides, owing to their high electrochemical activity are promising materials for chemical power sources (alkaline accumulators, lithium accumulators and hybrid supercapacitors), electrochromic devices, electrochemical oxidation of organic compounds. The most promising is nickel hydroxide that contains both α-Ni(OH)2 and β-Ni(OH)2. The aim of the research was to determine the properties of model mechanical mixtures with different ratios between α-Ni(OH)2 and β-Ni(OH)2 and to prove the hypothesis about the layered structure of nickel hydroxide samples synthesized in the slit diaphragm electrolyzer by means of comparative study.The XRD patterns of samples composed of α-Ni(OH)2 and β-Ni(OH)2 mixture show peaks corresponding to separate phases. By means of cyclic voltamperometry, it was discovered, that mixture samples do not show an oxidation peak during the first cycle, while two reduction peaks that correspond to reduction of α and β components are observed on the cathodic curve. A synergetic effect, which results in significant improvement in electrochemical activity of α-Ni(OH)2 and β-Ni(OH)2 mixture was discovered – specific reduction peak current values are 2.3 A/g (20 % α-phase), 3.5 A/g (30 % α-phase), 6.9 A/g (50 % α-phase), which exceed those of initial β-Ni(OH)2 (1.5 A/g) and α-Ni(OH)2 (2.0 A/g). By means of XRD analysis, it was discovered, that Ni(OH)2 samples synthesized in the SDE are composed of α and β and a series of intermediate structures. These samples demonstrate high electrochemical activity: presence of a defined oxidation peak during the first cycle, single reduction peaks with high specific currents of 6.5–11.7 A/g. The comparative analysis has revealed that electrochemically synthesized samples are composed of α-Ni(OH)2 and β-Ni(OH)2, but are not a mixture of these phases, owing to significantly different electrochemical behavior from mixture samples. Using mechanical modeling, the layered (α+β) structure of samples electrochemically synthesized in the slit diaphragm electrolyzer has been proved by contradiction.

Effect of stirring rates in anodic area of sediment microbial fuel cell on its power generation

ABSTRACTThe effect of stirring rates in anodic area of sediment microbial fuel cell on its operating performance, in terms of variations in power generation and sludge properties, was investigated in this work. The power density under 100 r/min stirring rate amounted to the highest peak value (98.8 mW/m2 for the 9th cycle). The volume average sizes of sludge flocs decreased with increasing the stirring rates, but the content of extracellular polymeric substances of sludge increased. According to cyclic voltammetry examination, significant improvement in electrochemical activity with microorganism growth was due to some kinds of mediating compounds produced in cell-associated form.

Electrophoretic Deposition of Nanoparticles into Three-Dimensional Felt As an Electrocataylst for the Solar Sulfur Ammonia Thermochemical Cycle

The penetration and coating of nanoparticles by electrophoretic deposition (EPD) into three-dimensional substrates was studied. Specifically, EPD of cobalt ferrite nanoparticles (20 nm) was investigated as a possible electrocatalyst to improve the kinetically slow anodic reaction of the oxidation of ammonium sulfite to ammonium sulfate in the hydrogen production sub-cycle of the solar sulfur-ammonia thermochemical water-splitting process. The primary goals were to uniformly penetrate and coat nanoparticles into 3D substrates by electrophoretic deposition and then to test their electrocatalytic activity by linear sweep voltammetry in 2 M ammonium sulfite. Electrophoretic deposition of cobalt ferrite nanoparticles from five bath compositions was performed on the following substrates: aluminum foil, graphite paper, 3 mm carbon felt, and 6 mm graphite felt. The bath compositions were 2 g/L of cobalt ferrite nanoparticles in 90/10 vol. % water/isopropanol with 1 mM (CHigh) or 0.05 mM (CLow) of hexadecyltrimethlyammonium bromide (CTAB), in 100% ethanol (E), in 100% acetylacetone (AA), and 100% acetylacetone with 0.2 wt. % polyethylenimine (AA-PEI). For electrophoretic deposition, a constant voltage was applied from 20 V to 128 V for a deposition time from 1 to 13 minutes. The zeta potential was measured to be 23 1 mV at pH of 6 for CHigh bath and 13 2 mV at pH 5 for E bath. Dry and wet adhesion of EPD deposits on aluminum was performed to determine adherence of nanoparticles to the substrate both after deposition and during the electrochemical process. Nanoparticles had good adherence to the substrate. To determine if nanoparticles could penetrate into 3D felt substrates by EPD, the ratio of Peclet number to Damköhler number (ratio of electrophoretic velocity to local deposition rate) was calculated to be greater than 1000, which indicated full penetration. Scanning electron microscopy (SEM) of the top and middle of the EPD deposits was used to examine the nanoparticle penetration and deposit morphology. It was confirmed by SEM images that there was full penetration and coating of nanoparticles into the 3 mm carbon felt and the 6 mm graphite felt from the 100% ethanol bath. The electrocatalytic activity of the EPD deposits on aluminum foil, graphite paper, 3 mm carbon felt, and 6 mm graphite felt substrates were analyzed by linear sweep voltammetry at 50 mV/s for the oxidation of 2 M ammonium sulfite. For the 3 mm carbon felt substrates, the highest electrochemical activity occurred on EPD deposits from the AA-PEI bath and then E bath. The highest electrochemical activity of the EPD deposits on 6 mm graphite felt occurred from the bath chemistries in decreasing order: CLow, AA-PEI, and E. The EPD deposit on 6 mm graphite felt from CLow bath obtained the highest electrochemical activity of all the deposits. For the 3 mm carbon felt, the ratio of current density of deposit compared to blank substrate ranged from 4 to 8 from E bath. The ratio of current density of EPD deposit on graphite paper and 6 mm graphite felt from E bath compared to blank substrate was about 1.6. The 3 mm carbon felt EPD deposits from AA-PEI bath ranged from 9 to 14, for the ratio of current density of the deposit compared to the blank substrate. EPD deposits from AA-PEI bath had a ratio of current density of deposit to blank substrate of 1.9 for deposits on aluminum foil, graphite paper, and 6 mm graphite felt. Overall, EPD was successful as a method to penetrate and coat cobalt ferrite nanoparticles up to 6 mm thick 3D felt. EPD deposits from AA-PEI bath improved the electrochemical activity compared to the blank substrate more than EPD deposits from E bath. But the EPD deposits from E bath were thin and uniform as well as deposited at much lower voltages compared to deposits from AA-PEI bath. EPD deposits from 3 mm carbon felt resulted in the largest improvement in electrochemical activity compared to the blank substrate from both E and AA-PEI bath. However, EPD deposits into 6 mm graphite felt had the highest electrochemical activity from all of the deposits. The EPD deposits with the highest electrochemical activity into 6 mm graphite felt in decreasing order were CLow, AA-PEI and E. The EPD conditions for these deposits were 40 V for 1 min from CLow resulting in current density of 75 mA/cm2, 127 V for 4 min from AA-PEI resulting in current density of 60 mA/cm2, and 40 V for 1 min from E resulting in current density of 38 mA/cm2.

Modification of carbon-metal composites using high-energy ball milling

A resorcinol-formaldehyde–nickel–palladium (RF–Ni–Pd) hydrogels were synthesized by sol–gel polycondensation followed by ambient drying. Carbon–nickel–palladium doped gels (C–Ni–Pd) were prepared by carbonising the RF–Ni–Pd gels at 900 °C in a nitrogen atmosphere. The goal of this study was to determine the effect of high-energy ball milling (HEBM) on the electrochemical activity of C–Ni–Pd composite. The scanning electron microscopy analysis, adsorption and X-ray diffraction measurements showed that the HEBM of C–Ni–Pd composite resulted in the modification of the morphological, porous and crystalline features of the carbon matrix. It has been demonstrated that composite C–Ni–Pd composed of sphere-like granules incrusted with well-crystalline nickel and palladium particles exhibits electrochemical activity in 6 M KOH aqueous solution. High-energy ball milling of the composite brought about the improvement of electrochemical activity in the potential range of the hydrogen sorption/desorption reaction.

Array of Cu2O nano-columns fabricated by oblique angle sputter deposition and their application in photo-assisted proton reduction

Nano-columnar arrays of Cu2O were grown by the oblique angle sputter deposition technique based on the self-shadowing principle. The as-grown nano-columnar samples are oriented along {111} direction, and they are highly transmitting in the visible range with a low reflectance. In this work, we show the photo-electrochemical activity of nano-columnar array of Cu2O, which shows a higher (∼25%) photocurrent density and a two-fold enhancement in the incident-to-photon conversion efficiency as compared to continuous thin film of Cu2O in photo-assisted proton reduction type reaction. The improvement in electrochemical activity of nano-columnar Cu2O photocathode can be attributed to the change in morphology, crystal structure, as well as electrical property, which shows a higher degree of band bending, increased donor carrier (e−) density and lower width of space charge region as revealed by capacitance measurements and Mott-Schottky analysis.

Improvement of Electrochemical Activity of Pt/MWCNT Catalyst for Proton Exchange Membrane Fuel Cell

In last years, the carbon nanotubes have been studied as an advanced metal catalyst support for proton exchange membrane fuel cell. This study focuses on the sonochemical treatment of multi walled carbon nanotubes (MWCNTs) as a platinum supporting material for proton exchange membrane fuel cell (PEMFC) by mixture of sulfuric acid and nitric acid and mixture of sulfuric acid and hydrogen peroxide. X-ray diffraction (XRD) and Infrared (IR) spectroscopy were used to characterize the surface of sonochemically treated MWCNT and nanostructured electrocatalyst Pt/MWCNT. According to the experimental results of this work, the surface of MWCNT can be more successfully functionalized with hydroxyl and carboxyl groups after sonochemical treatment by mixture of sulfuric acid and nitric acid. The particle size of prepared Pt -electrocatalyst on MWCNT was determined 3.4 nm by XRD.DOI: http://dx.doi.org/10.5564/mjc.v12i0.165 Mongolian Journal of Chemistry Vol.12 2011: 20-23

Improvement of power generation using Shewanella putrefaciens mediated bioanode in a single chambered microbial fuel cell: effect of different anodic operating conditions.

Three different approaches were employed to improve single chambered microbial fuel cell (sMFC) performance using Shewanella putrefaciens as biocatalyst. Taguchi design was used to identify the key process parameter (anolyte concentration, CaCl₂ and initial anolyte pH) for maximization of volumetric power. Supplementation of CaCl₂ was found most significant and maximum power density of 4.92 W/m(3) was achieved. In subsequent approaches, effect on power output by riboflavin supplementation to anolyte and anode surface modification using nano-hematite (Fe₂O₃) was observed. Volumetric power density was increased by 44% with addition of 100 nM riboflavin to anolyte while with 0.8 mg/cm(2) nano-Fe₂O₃ impregnated anode power density and columbic efficiency increased by 40% and 33% respectively. Cyclic voltammetry revealed improvement in electrochemical activity of Shewanella with nano-Fe₂O₃ loading and electrochemical impedance depicted inverse relationship between charge transfer resistance and nano-Fe₂O₃ loading. This study suggests anodic improvement strategies for maximization of power output.

The influence of thermal treatment on the electrochemical properties of carbon–Ni–Pd composites

Resorcinol–formaldehyde (RF) hydrogel and RF–nickel–palladium (RF–Ni–Pd) hydrogel were synthesized by sol–gel polycondensation followed by ambient drying. Carbon gel and carbon–nickel–palladium doped gels were prepared by carbonizing the RF and RF–Ni–Pd gels at 900 °C under a nitrogen atmosphere. The goal of this study was to determine the effect of oxidative thermal treatment on the electrochemical activity of nickel–palladium doped carbon gels (C–Ni–Pd). The scanning electron microscopy analysis, adsorption and X-ray diffraction measurements showed that the admixture of Ni and Pd to carbon matrix resulted in the modification of morphological, porous and crystalline features. It has been demonstrated that composite C–Ni–Pd composed of sphere-like granules incrusted with well-crystalline nickel and palladium particles exhibits electrochemical activity in 6 M KOH aqueous solution. Thermal treatment of the composite carried out in air at 450 °C brought about the improvement of electrochemical activity in the potential range of the hydrogen sorption/desorption reaction.

Tuning the Electronic Structure of Titanium Oxide Support to Enhance the Electrochemical Activity of Platinum Nanoparticles

Two times higher activity and three times higher stability in methanol oxidation reaction, a 0.12 V negative shift of the CO oxidation peak potential, and a 0.07 V positive shift of the oxygen reaction potential compared to Pt nanoparticles on pristine TiO2 support were achieved by tuning the electronic structure of the titanium oxide support of Pt nanoparticle catalysts. This was accomplished by adding oxygen vacancies or doping with fluorine. Experimental trends are interpreted in the context of an electronic structure model, showing an improvement in electrochemical activity when the Fermi level of the support material in Pt/TiOx systems is close to the Pt Fermi level and the redox potential of the reaction. The present approach provides guidance for the selection of the support material of Pt/TiOx systems and may be applied to other metal-oxide support materials, thus having direct implications in the design and optimization of fuel cell catalyst supports.

Improvement of Electrochemical Activity of Pt/MWCNT Catalyst for Proton Exchange Membrane Fuel Cell

ABSTRACTIn last years, the carbon nanotubes have been studied as an advanced metal catalyst support for proton exchange membrane fuel cell. This study focuses on the sonochemical treatment of multi walled carbon nanotubes (MWCNTs) as a platinum supporting material for proton exchange membrane fuel cell (PEMFC) by mixture of sulfuric acid and nitric acid and mixture of sulfuric acid and hydrogen peroxide. X-ray diffraction (XRD) and Infrared (IR) spectroscopy were used to characterize the surface of sonochemically treated MWCNT and nanostructured electrocatalyst Pt/MWCNT. According to the experimental results of this work, the surface of MWCNT can be more successfully functionalized with hydroxyl and carboxyl groups after sonochemical treatment by mixture of sulfuric acid and nitric acid. The particle size of prepared Pt -electrocatalyst on MWCNT was determined 3.4 nm by XRD.

Pt/CNT-Based Electrodes with High Electrochemical Activity and Stability for Proton Exchange Membrane Fuel Cells

An integrated platinum/carbon nanotube (CNT)-based electrode for proton exchange membrane fuel cells has been efficiently fabricated by the in situ growth of a CNT layer onto carbon paper and by a subsequent direct sputter deposition of a Pt catalyst. Scanning electron microscopy and Raman spectroscopy demonstrated that the CNTs directly grown onto carbon paper formed a dense CNT layer with high surface roughness and porosity. Transmission electron microscopy micrographs indicated that this Pt/CNT composite catalyst consists of numerous Pt nanoparticles that are uniformly dispersed on the CNT surface without any surface oxidation treatment. X-ray photoelectron spectroscopy analysis revealed that the sputter-deposited Pt catalysts are mainly in a pure metallic state with an extremely low oxide formation. Compared with the carbon-black-based electrode with commercial Pt/VXC72R catalysts, the Pt/CNT/carbon-paper-based electrode has shown a pronounced improvement in electrochemical activity and stability, verified by polarization performance tests and in situ accelerated degradation tests. In situ cyclic voltammetry measurements further confirmed that the integrated Pt/CNT catalyst could give rise to a higher Pt utilization and a better corrosion resistance at the cathode.

Characterization of electrodeposited WO 3 films and its application to electrochemical wastewater treatment

WO 3 films have been prepared on to IrO 2-coated Ti substrate by cathodic deposition, and as-deposited and annealed films have been characterized using XRD, TEM, Raman and FT-IR spectroscopy. The as-deposited film consists of nanocrystalline, orthorhombic WO 3·H 2O and this phase transforms to amorphous WO 3 by annealing at 250 °C and to monoclinic WO 3 by annealing at and above 350 °C. The as-deposited and annealed films have been used as anodes for electrochemical decomposition of phenol in aqueous solutions with and without chloride ions. The monoclinic WO 3 anodes prepared by annealing at 350 and 400 °C show relatively high electrochemical activity in the chloride-containing solution. In addition, the anodes possess high chemical and physical stabilities: very low dissolution rate of WO 3 during the electrolysis and good adhesion to the substrate. Thus, WO 3 anodes may be promising materials for anodic oxidation of bio-refractory organics in wastewater, although further improvement of electrochemical activity is needed for more effective decrease in total organic carbons in wastewater.