Methanol In Alkaline Solution Research Articles

One-pot facile decoration of graphene nanosheets with Ag nanoparticles for electrochemical oxidation of methanol in alkaline solution

Hybrid nanomaterials (GAg) of graphene nanosheets and Ag nanoparticles (Ag NPs) were prepared by a one-pot reduction of both Ag+ and graphene oxide (GO), and studied for electrochemical oxidation of methanol in alkaline solution. From TEM, XRD and other measurements, the crystalline Ag NPs with a typical diameter of 5–15nm were homogeneously decorated on graphene nanosheets without aggregation, while their densities (25.6%–61.0%) could be easily controlled by changing the synthesis ratio of graphene oxide nanosheets to Ag+. Cyclic voltammograms results reveal that the GAg materials had the increased electrocatalytic activity (reversed catalytic peak current: 0.22×10−5 A–1.01×10−5 A) with the increase of Ag NPs loading for methanol oxidation in alkaline solution, and the catalytic current was linear to the concentration of CH3OH. At last, the stability of GAg catalysts-modified electrodes and the influence of catalytic reaction temperature towards methanol oxidation were also investigated. The facile synthesis, low cost and high activity of the GAg materials make them have great potential applications in the direct methanol alkaline fuel cells (DMAFCs).

Dimerization of 1-Phenyl-1<i>H</i>-Tetrazole-5-Thiol over Metalloporphyrin Catalysts

In an alkaline methanol solution, dimerization of 1-phenyl-1H-tetrazole-5-thiol (HL) was carried out over metalloporphyrin catalysts under mild conditions. The dimer product, 1,2-bis (1-phenyl-1H-tetrazol-5-yl) disulfane (L-L), was characterized by determinations of infrared (IR), HPLC, NMR and elementary analysis respectively. In situ UV-Vis spectroscopic analysis and cyclic voltammetric (CV) determinations suggested that the active intermediate for L-L formation is an axially ligated complex, RS-MnⅢTHPP, which decomposes into a MnⅡTHPP molecule and a stable radical (SR) for coupling to form the disulfane. Meanwhile MnIITHPP molecule can be oxidized easily to form MnⅢTHPP species again by oxygen from the air for using in next catalytic circle.

A comparative investigation of the electrocatalytic oxidation of methanol on poly-NiTCPP and poly-TCPP/Ni modified glassy carbon electrodes

Electro-oxidation of methanol in alkaline solution at a glassy carbon electrode electrochemically modified by a conductive polymeric meso-tetra(4-carboxyphenyl)porphyrinato nickel(II), abbreviated as poly-NiTCPP and also meso-tetra(4-carboxyphenyl)porphyrin with incorporated nickel(II) cations, abbreviated as, poly-TCPP/Ni, were investigated and compared. Both films were prepared by oxidative electro-polymerization of complexes by repetitive cyclic voltammetry (RCV) in 0.1M NaOH aqueous solution. The electrochemical properties and behaviors and also kinetic values of both films have been characterized and compared using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). Similar rate constants (1.48×105 and 1.40×105cm3mol−1s−1) and also, the electron transfer coefficients (α=0.54 and 0.58) were determined for methanol electro-oxidation on the surface of GC/poly-NiTCPP and GC/poly-TCPP/Ni electrodes, respectively. Impedance spectroscopy was used to investigate the catalytic oxidation of methanol on the surface of the modified electrodes. Finally, it has been shown that the both electrodes have an acceptable long-term (checked up to 1month) stability toward methanol oxidation.

Photooxidation of Alkaloids: Considerable Quantum Yield Enhancement by Rose Bengal‐sensitized Singlet Molecular Oxygen Generation

The photooxidation of sanguinarine, coralyne and berberine was studied in oxygenated alkaline methanol solutions. Rose bengal as photosensitizer significantly accelerates the process, indicating the importance of singlet molecular oxygen in the reaction mechanism. The quantum yield of sensitized oxidation was found to increase significantly with pH and reaches 0.4 for berberine at pH 13.8. The direct oxidation of alkaloids is less efficient, the quantum yield does not exceed 0.01 even in oxygen-saturated solutions. The photoinduced electron ejection does not play a role in the oxidation. The uncharged pseudobase forms, which are present in alkaline medium, are oxidized much more easily than the alkaloid cations.

Copper-poly(2-aminodiphenylamine) as a novel and low cost electrocatalyst for electrocatalytic oxidation of methanol in alkaline solution

In the present work we demonstrate the carbon paste as a new electrode substrate for the electropolymerization of 2-aminodiphenylamine and fabrication of polymer film modified electrode. Then transition metal of copper is incorporated into the polymer by electrodepositing of Cu(II) from CuCl 2 acidic solution using potentiostatic technique. The electrocatalytic oxidation of methanol was studies by cyclic voltammetry and chronoamperometry methods at the surface of obtained Cu/P(2ADPA)/MCPE. It has been found that in the course of an anodic potential sweep, the electro-oxidation of methanol follows the formation of Cu(III) and is catalyzed by this species through a mediated electron transfer mechanism. The obtained current density for this catalytic oxidation is very high which could be come from high surface area of caused by the P(2ADPA) modification. The effects of various parameters such as the copper loading, scan rate and methanol concentration on the electrocatalytic oxidation of methanol were also investigated at the surface of Cu/P(2ADPA)/MCPE. Finally, using a chronoamperometric method, the catalytic rate constant ( k) for methanol was found to be 0.2 × 10 5 cm 3 mol −1 s −1 that the high k can be ascribed for the fast electron transfer process due to electrode modification.

RETRACTED: Fabrication and characterization of non-platinum electrocatalyst for methanol oxidation in alkaline medium: Nickel nanoparticles modified carbon-ceramic electrode

The use of carbon-ceramic electrode (CCE) modified with nickel nanoparticles was studied for the electrocatalytic oxidation of methanol in alkaline medium by cyclic voltammetry and chronoamperometry. After preparation of the carbon-ceramic by sol—gel technique as the electrode matrix, its surface was potentiostatically coated with Ni nanoparticles at ―600 mV vs. SCE in an aqueous solution of 0.1 M Na 2 SO 4 (pH = 3.8) containing 5 mM NiCl 2 . The CCE modified with nickel nanoparticles (CCE/Ni) was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and cyclic voltammetry and used as electrocatalyst for oxidation of methanol in alkaline solution. It was shown that the CCE/Ni was the most efficient catalyst in the oxidation of methanol making it more attractive for fuel cell applications. The effective parameters on electrocatalytic oxidation of methanol such as the Ni loading procedure, amount of Ni loading and methanol concentration were investigated and the results were discussed. Finally, the long-term stability of the modified electrode has also been investigated.

Electrochemical behavior of Ni(II) incorporated in zeolite Y-modified carbon electrode: application for electrocatalytic oxidation of methanol in alkaline solution

Nickel ions were incorporated in NaY zeolite according to cation exchange mechanism. Then NiY zeolite was used as modifier for preparation of modified carbon paste electrode. The electrochemical behavior of NiY-modified carbon paste electrode (NiY/CPE) was studied in alkaline solution using cyclic voltammetry method. Ability of different electrodes containing NiY/CPE, Ni-NiY/CPE, Ni-NaY/CPE, and Ni/CPE for electrocatalytic oxidation of methanol was compared (three last electrodes prepared by open circuit accumulation of Ni(II) ions on the surface of NiY/CPE, NaY/CPE, and bare CPE, respectively). Results show that Ni-NiY/CPE is best catalyst for the electrochemical oxidation of methanol in alkaline solution and both process of earlier Ni ion incorporation through cation exchange in NaY zeolite and open circuit accumulation of Ni ion on the surface of electrode are essential to have good catalyst. Effect of graphite–zeolite ratio on electrocatalytic current was studied and 3:1 ratio of graphite–zeolite was selected as optimum ratio for preparing electrode. Ni-NiY/CPE has very good stability toward the methanol oxidation in concentration range of 0.005 to 0.5 M. Finally, using chronoamperometric method, the catalytic rate constant (k) for methanol was found to be 1.56 × 104 cm3 mol−1 s−1.

Electrochemical quartz crystal microbalance study on Au-supported Pt adlayers for electrocatalytic oxidation of methanol in alkaline solution

Underpotential deposition (UPD) of Cu on an Au electrode followed by redox replacement reaction (RRR) of CuUPD with a Pt source (H2PtCl6 or K2PtCl4) yielded Au-supported Pt adlayers (for short, Pt(CuUPD-Pt4+)n/Au for H2PtCl6, or Pt(CuUPD-Pt2+)n/Au for K2PtCl4, where n denotes the number of UPD-redox replacement cycles). The electrochemical quartz crystal microbalance (EQCM) technique was used for the first time to quantitatively study the fabricated electrodes and estimate their mass-normalized specific electrocatalytic activity (SECA) for methanol oxidation in alkaline solution. In comparison with Pt(CuUPD-Pt2+)n/Au, Pt(CuUPD-Pt4+)n/Au exhibited a higher electrocatalytic activity, and the maximum SECA was obtained to be as high as 35.7 mA μg−1 at Pt(CuUPD-Pt4+)3/Au. The layer-by-layer architecture of Pt atoms on Au is briefly discussed based on the EQCM-revealed redox replacement efficiency, and the calculated distribution percentages of bare Au sites agree with the experimental results deduced from the charge under the AuO x -reduction peaks. The EQCM is highly recommended as an efficient technique to quantitatively examine various electrode-supported catalyst adlayers, and the highly efficient catalyst adlayers of noble metals are promising in electrocatalysis relevant to biological, energy and environmental sciences and technologies.

An electrochemical methanol sensor based on a Pd–Ni/SiNWs catalytic electrode

A novel electrochemical methanol sensor based on a catalytic electrode of palladium-nickel/silicon nanowires (Pd–Ni/SiNWs) is presented in this paper. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and electrochemical methods are employed to investigate the Pd–Ni/SiNWs electrode materials. These nanocomposite materials exhibit a highly ordered, wire-like structure with a wire length of ∼50 μm and a wire diameter ranging from 100 to 300 nm. The substrate has good electrocatalytic activity towards the oxidation of methanol in alkaline solutions. The performances of the prototype sensor are characterized by cyclic voltammetry and fixed potential amperometry techniques. In a 1 mol L −1 KOH solution containing different methanol concentrations, the sensor exhibits a good sensitivity of 1.96 mA mmol −1 L cm −2 with R 2 = 0.99 and the corresponding detection limit of 18 μmol L −1 (signal-to-noise ratio = 3, S/N = 3) for cyclic voltammetry. Meanwhile, the electrode also displays a sensitivity of 0.48 mA mmol −1 L cm −2 with R 2 = 0.98 and the corresponding detection limit of 25 μmol L −1 (S/N = 3) for a fixed potential amperometry at −0.3 V versus an Ag/AgCl reference electrode. The results demonstrate that the Pd–Ni/SiNWs catalytic electrode has potential as an efficient and integrated sensor for methanol detection.

The Determination of Methanol Using an Electrolytically Fabricated Nickel Microparticle Modified Boron Doped Diamond Electrode

AbstractA nickel modified boron doped diamond (Ni‐BDD) electrode and nickel foil electrode were used in the determination of methanol in alkaline solutions. The Ni‐BDD electrode was electrodeposited from a 1 mM Ni(NO3)2 solution (pH 5), followed by repeat cycling in KOH. Subsequent analysis utilised the Ni(OH)2/NiOOH redox couple to electrocatalyse the oxidation of methanol. Methanol was determined to limits of 0.3 mM with a sensitivity of 110 nA/mM at the Ni‐BDD electrode. The foil electrode was less sensitive achieving a limit of 1.6 mM and sensitivity of 27 nA/mM. SEM analysis of the electrodes found the Ni‐BDD to be modified by a quasi‐random microparticle array.

Electrooxidation of methanol on NiMn alloy modified graphite electrode

Nickel and nickel–manganese alloy modified graphite electrodes (G/Ni and G/NiMn) prepared by galvanostatic deposition were examined for their redox process and electrocatalytic activities towards the oxidation of methanol in alkaline solutions. The methods of cyclic voltammetery (CV), chronoamperometry (CA) and impedance spectroscopy (EIS) were employed. In CV studies, in the presence of methanol NiMn alloy modified electrode shows a significantly higher response for methanol oxidation. The peak current of the oxidation of nickel hydroxide increase is followed by a decrease in the corresponding cathodic current in presence of methanol. The anodic peak currents show linear dependency upon the square root of scan rate. This behavior is the characteristic of a diffusion controlled process. Under the CA regime the reaction followed a Cottrellian behavior and the diffusion coefficient of methanol was found to be 4 × 10 −6 cm 2 s −1. A mechanism based on the electro-chemical generation of Ni 3+ active sites and their subsequent consumptions by methanol have been discussed and the corresponding rate law under the control of charge transfer has been developed and kinetic parameters have been derived. The charge transfer resistance accessible both theoretically and through the EIS have been used as criteria for derivation of the rate constant.

Hydrogen Generation from Alkaline Solutions of Methanol and Ethanol by Electrolysis

In this study, electrolysis of alkaline methanol and ethanol solutions was carried out on platinized electrodes in actual cells with different cell preparation and catalyst coating methods. The electrolysis reaction products were analyzed by X-Ray and titrimetric methods. The gas phase products were analyzed by Gas Chromatography technique. Thermodynamic calculations and analysis results suggest that the carbonate formation is highly favorable in alkaline KOH solutions. However, methane formation reaction along with carbonate and oxygen formations may be possible during ethanol electrolysis. Alkaline methanol solutions were electrolyzed easily using platinum coated carbon paper electrodes. It was found that Nafion based MEA's are not essential for electrolysis of alkaline solutions of methanol and ethanol. One of the best performances was obtained using micro porous polyethersulfone membranes in a special cell configuration.

A study of the electrocatalytic oxidation of methanol on a nickel–salophen-modified glassy carbon electrode

Nickel–salophen-modified glassy carbon electrodes prepared by transferring one drop of Ni–salophen complex solution on the electrode surface. This modified electrode has been used for the electrocatalytic oxidation of methanol in alkaline solutions with various methods such as cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The electrooxidation was observed as large anodic peaks, and early stages of the cathodic direction of potential sweep around 20 mV vs. Ag|AgCl|KClsat. A mechanism based on the electrochemical generation of Ni (Ш) active sites and their subsequent consumptions by methanol have been discussed. EIS studies were employed to unveil the charge transfer rate as well as the electrical characteristics of the catalytic surface. For the electrochemical oxidation of methanol at 5.0 M concentration, charge transfer resistance of nearly 0.936 kΩ was obtained, while the resistance of the electrocatalyst layer was about 111.6 Ω.

The Influence of Platinum Surface Morphology on the Electrooxidation of Methanol in Alkaline Solutions

In this work we compare methanol oxidation characteristics in pH 0 and pH 14 electrolytes, and examine the effect of methanol concentration and platinum surface condition (e.g. H-UPD, OH adsorption, Pt oxidation/reduction, planar, nanoporous) on the oxidation current. We observe that in rotating disc electrode (RDE) experiments the oxidation currents on smooth platinum decrease with increasing rotation rate. We show that this decrease is associated with increasing the rate at which oxidation intermediates are swept into the bulk electrolyte before being fully oxidized. To increase the dwell time of intermediates a platinum electrode with 3 nm length scale surface porosity was synthesized by dealloying a Pt-Cu alloy. We then perform the same RDE experiments and show that in this case the methanol oxidation current increases with increasing convection. We attribute this behavior to the trapping of reaction intermediates that otherwise were swept away on the polished sample.

Intramolecular Fluorescence Resonance-energy-transfer of Fluorescein Derivative; Phenyl and Styryl p-Disubstituted Fluorescein

Abstract We describe synthesis and fluorescence properties of phenyl and styryl p-disubstituted fluorescein. The compound was synthesized in three reaction steps from trans,trans,trans-1,6-diphenyl-1,3,5-hexatriene. The fluorescence spectrum of the product in alkaline methanol solution suggested occurrence of intramolecular FRET from the donor site of the benzene moiety to the acceptor site of the xanthene moiety.

Nickel–poly(o-aminophenol)-modified carbon paste electrode; an electrocatalyst for methanol oxidation

In this work, a modified carbon paste electrode consisting of Nickel dispersed in poly(ortho-aminophenol) was used for electrocatalytic oxidation of methanol in alkaline solution. A carbon paste electrode bulk modified with o-aminophenol was used for polymer preparation by cyclic voltammetry method; then, Ni(II) ions were incorporated by immersion of the modified electrode in 1 M Ni(II) ion solution at open circuit. The electrochemical characterization of this modified electrode exhibits stable redox behavior of the Ni(III)–Ni(II) couple. Electrocatalytic oxidation of methanol on the surface of modified electrode was investigated with cyclic voltammetry and chronoamperometry methods, and the dependence of the oxidation current and shape of cyclic voltammograms on methanol concentration and scan rate were discussed. Also, long-term stability of modified electrode for electrocatalytic oxidation of methanol was investigated.

Electrocatalytic oxidation of methanol on Ni and NiCu alloy modified glassy carbon electrode

Nickel and nickel–copper alloy modified glassy carbon electrodes (GC/Ni and GC/NiCu) prepared by galvanostatic deposition were examined for their redox process and electrocatalytic activities towards the oxidation of methanol in alkaline solutions. The methods of cyclic voltammetery (CV) and chronoamperometry (CA) were employed. The cyclic voltammogram of NiCu alloy demonstrates the formation of β/β crystallographic forms of the nickel oxyhydroxide under prolonged repetitive potential cycling in alkaline solution. In CV studies, in the presence of methanol NiCu alloy modified electrode shows a significantly higher response for methanol oxidation. The peak current of the oxidation of nickel hydroxide increase is followed by a decrease in the corresponding cathodic current in presence of methanol. The anodic peak currents show linear dependency with the square root of scan rate. This behavior is the characteristic of a diffusion controlled process. Under the CA regime the reaction followed a Cottrellian behavior and the diffusion coefficient of methanol was found to be 2 × 10 −6 cm 2 s −1 in agreement with the values obtained from CV measurements.

The Influence of Platinum Surface Morphology on the Electrooxidation of Methanol in Alkaline Solutions

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Preparation of glass carbon electrode modified with nanocrystalline nickel-decorated carbon nanotubes and electrocatalytic oxidation of methanol in alkaline solution

Nanocrystalline nickel with an average diameter of about 16 nm and a face-centered cubic (fcc) structure was uniformly attached to the surface of carbon nanotubes (CNT) by wet chemistry. The sample was characterized by X-ray powder diffraction and transmission electron microscopy (TEM). A glass carbon electrode modified with nickel-modified multi-wall carbon nanotubes (MWCNTs-Ni/GCE) was prepared. The electrochemical behavior of the MWCNTs-Ni/GCE and the electrocatalytic oxidation of methanol at the MWCNTs-Ni/GCE were investigated by cyclic voltammetry in 1.0 mol/L NaOH solution. The cyclic voltammograms showed that the electron transfer between β-Ni(OH)2 and β-NiOOH is mainly a diffusion-controlled quasireversible process, and that the electrode has high catalytic activity for the electrooxidation of methanol in alkaline medium, revealing its potential application in alkaline rechargeable batteries and fuel cells.

Formation of a Unique Zinc Carbamate by CO2 Fixation: Implications for the Reactivity of Tetra-Azamacrocycle Ligated Zn(II) Complexes

The macrocyclic ligand [13]aneN 4 ( L1, 1,4,7,10-tetra-azacyclotridecane) was reacted with Zn(II) perchlorate and CO 2 in an alkaline methanol solution. It was found that, by means of subtle changes in reaction conditions, two types of complexes can be obtained: (a) the mu 3 carbonate complex 1, {[Zn( L1)] 3(mu 3-CO 3)}(ClO 4) 4, rhombohedral crystals, space group R3 c, with pentacoordinate zinc in a trigonal bipyramidal enviroment, and (b) an unprecedenced dimeric Zn(II) carbamate structure, 2, [Zn( L2)] 2(ClO 4) 2, monoclinic crystals, space group P2 1/ n. The ligand L2 (4-carboxyl-1,4,7,10-tetra-azacyclotridecane) is a carbamate derivative of L1, obtained by transformation of a hydrogen atom of one of the NH moieties into carbamate by means of CO 2 uptake. In compound 2, the distorted tetrahedral Zn(II) coordinates to the carbamate moiety in a monodentate manner. Most notably, carbamate formation can occur upon reaction of CO 2 with the [Zn L1] (2+) complex, which implicates that a Zn-N linkage is cleaved upon attack of CO 2. Since complexes of tetra-azamacrocycles and Zn(II) are routinely applied for enzyme model studies, this finding implies that the Zn-azamacrocycle moiety generally should no longer be considered to play always only an innocent role in reactions. Rather, its reactivity has to be taken into account in respective investigations. In the presence of water, 2 is transformed readily into carbonate 1. Both compounds have been additionally characterized by solid-state NMR and infrared spectroscopy. A thorough comparison of 1 with related azamacrocycle ligated zinc(II) carbonates as well as a discussion of plausible reaction paths for the formation of 2 are given. Furthermore, the infrared absorptions of the carbamate moiety have been assigned by calculating the vibrational modes of the carbamate complex using DFT methods and the vibrational spectroscopy calculation program package SNF.