Electrocatalytic Activity of Nanocomposites of Sulphur Doped Graphene Oxide and Nanosized Cobalt Phthalocyanines

In this work we explore the electrocatalytic activity of nanocomposites of reduced sulphur doped graphene oxide nanosheets (rSDGONS) and cobalt phthalocyanine (CoPc) or cobalt tetra amino phthalocyanine (CoTAPc) towards hydrogen peroxide. Transmission electron microscopy, scanning electron microscopy, X‐ray photon spectroscopy, X‐ray diffraction, chronoamperometry, linear scan voltammetry and cyclic voltammetry were used to characterize the nanocomposites. Nanosized CoPc showed superior (in terms of currents) electrocatalytic oxidation and reduction of hydrogen peroxide compared to CoTAPc nanoparticles (CoTAPc NP ). The lowest detection limit was obtained for hydrogen peroxide oxidation on electrodes modified with CoPc NP ‐rSDGONS at 1.49 µM. The same electrode gave a high adsorption equilibrium constant of 1.27×10³ mol^?1 and a Gibbs free energy of ?17.71 kJ/mol, indicative of a spontaneous reaction on the electrode surface.     

Voltammetry of a Benzoquinone–Hydroquinone Redox Couple at Electrodes Modified with a Polyvinylpyridine Film Doped with Cobalt Phthalocyanine

The electrochemical properties of a glassy-carbon electrode coated with a polyvinylpyridine film doped with incorporated cobalt phthalocyanine were studied in a reaction involving a benzoquinone–hydroquinone redox couple. It was found that poly-(2-vinylpyridine) film applied to the electrode and cobalt phthalocyanine deposited onto it or incorporated in the polymeric film exhibited electrocatalytic activity on the oxidation of hydroquinone. Conditions were selected for obtaining a polyvinylpyridine film doped with cobalt phthalocyanine on the electrode surface providing a maximum catalytic effect. The current of the hydroquinone oxidation peak and the current of the reverse benzoquinone reduction peak at the chemically modified electrode were linear functions of their concentrations in the range from 1 × 10^–6 to 1 × 10^–3 M.     

Preparation of nanostructured Co–Mo alloy electrodes and investigation of their electrocatalytic activity for hydrazine oxidation in alkaline medium

Cobalt and cobalt–molybdenum alloy electrodes are prepared by galvanic deposition on copper substrates. In this paper, we report a study on the influence of alloying cobalt with molybdenum for the oxidation of hydrazine in 1 M NaOH aqueous solutions. The electrocatalytic properties of the electrodes are studied by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM), X‐ray diffraction (XRD), energy‐dispersive X‐ray spectroscopy (EDS,) and inductively coupled plasma (ICP) analysis demonstrate that the structural features and compositions of the as‐prepared Co–Mo coatings vary with the deposition conditions. Electrochemical characterization indicates that the electrochemical properties and the electrocatalytic activity of the investigated alloys were strongly dependent on the microstructural features obtained under different deposition conditions. The overall experimental data indicate that alloying cobalt with molybdenum metal leads to an increase of the electrocatalytic activity in hydrazine electroxidation compared to when using the pure cobalt electrode. High catalytic efficiencies were achieved on Co/25 at.% Mo and Co/33 at.% Mo electrodes, the latter being the best electrocatalyst for hydrazine electroxidation.     

Metal Phthalocyanine‐Porphyrin‐based Conjugated Microporous Polymer‐derived Bifunctional Electrocatalysts for Zn‐Air Batteries

Conjugated microporous polymers (CMPs) as emerging porous materials with diverse structures and tunable building‐units have attracted much attention in the electrochemical field. Herein, we designed phthalocyanine‐porphyrin‐based conjugated microporous polymers as precursors for fabrication of Co, Fe, N tri‐doped graphene composites towards oxygen reduction and evolution reaction (ORR/OER). As expected, the elements cobalt and iron are well dispersed in graphene carbon and interact with the nitrogen sites, thereby providing extra electrocatalytic active sites and enhancing its overall conductivity. Benefiting from its unique design and structure, the obtained catalyst affords a superior bifunctional catalytic activity with a positive onset potential of 0.957 V for ORR, and a low overpotential of 0.36 V for OER. More attractively, the CoFeNG is employed as an air cathode catalyst in Zn‐air batteries, showing a maximum current density of 215 mA cm^?2 and good cycle stability for 20000 s. The rational design of phthalocyanine‐porphyrin‐based derivatives provides a feasible route for the construction of high‐performance ORR/OER catalysts.     

Effect of detonation nanodiamonds on the electrocatalytic activity of asymmetric cobalt phthalocyanine: Covalent versus non-covalent linking

We report on the effect of detonation nanodiamonds (DNDs) on electrocatalytic properties of an asymmetrically substituted cobalt phthalocyanine (CoPc). The incorporation of DNDs onto cobalt phthalocyanine enhances its electrochemical behaviour. An asymmetrical CoPc alone, when π-π stacked (CoPc-DNDs(ππ)) or covalently linked (CoPc@DNDs) to DNDs is used to modify a glassy carbon electrode (GCE) for the electrocatalytic detection of hydrazine. In addition, the GCE was modified by sequentially adding CoPc and DNDs onto its surface, represented as GCE/CoPc-DNDs(seq) when CoPc is placed before DNDs on the electrode and GCE/DNDs-CoPc(seq) when DNDs are placed before CoPc, where seq represents sequential. The obtained catalytic rate for the detection of hydrazine on GCE/CoPc@DNDs was 9.3×10⁴ M⁻¹.s⁻¹ with a limit of detection as 0.33 μM. GCE/CoPc@DNDs gave better electrocatalytic activities when compared to its counterparts.     

Anthracene Substituted Co (II) and Cu (II) phthalocyanines; Preparations,Investigation of Catalytical and Electrochemical Behaviors

An approach to investigation of catalytical behaviors of Co (II) and Cu (II) phthalocyanines is reported that is based on changing any parameter to effect these behaviors. Towards this end, new anthracene substituted Co (II) and Cu (II) phthalocyanines were prepared and characterized spectroscopic methods. New cobalt (II) and copper (II) phthalocyanines were used as catalyst for oxidation of different phenolic compounds (such as 2,3‐dichlorophenol, 4‐methoxyphenol, 4‐nitrophenol, 2,3,6‐trimethylphenol) with different oxidants. Then, electrochemical characterization of cobalt (II) and copper (II) phthallocyanines were determined by using cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. Although copper (II) phthalocyanine showed similar Pc based electron transfer processes, cobalt (II) phthalocyanine showed metal and ligand based reduction reactions as expected.     

Electrode Modification through Click Chemistry Using Ni and Co Alkyne Phthalocyanines for Electrocatalytic Detection of Hydrazine

This work reports on the development of sensors for the detection of hydrazine using glassy carbon electrodes (GCE) modified with phthalocyanines through click chemistry. Tetrakis(5‐hexyn‐oxy) cobalt(II) phthalocyanine (complex 2 ) and tetrakis(5‐hexyn‐oxy) nickel(II) phthalocyanine (complex 3 ) were employed as electrode modifiers for hydrazine detection. The GCE was first grafted via the in situ diazotization of a diazonium salt, rendering the GCE surface layered with azide groups. From this point, the 1, 3‐dipolar cycloaddition reaction, catalysed by a copper catalyst was utilised to “click” the phthalocyanines to the surface of the grafted GCE. The modified electrodes were characterized by scanning electrochemical microscopy, X‐ray photoelectron spectroscopy and cyclic voltammetry. The electrografted CoP 2 ‐clicked‐GCE and NiP 3 ‐clicked‐GCE exhibited electrocatalytic activity towards the detection of hydrazine. The limit of detection (LoD) for the CoPc‐GCE was 6.09 μM, while the NiPc‐GCE had a LoD of 8.69 μM. The sensitivity was 51.32 μA mM⁻¹ for the CoPc‐GCE and 111.2 μA mM⁻¹ for the NiPc‐GCE.     

双核钴锰酞菁对SOCl2还原反应的电催化性能

为了确定双核金属酞菁化合物对亚硫酰氯还原反应是否具有比单核金属酞菁更强的电催化性能, 通过循环伏安测试方法, 用酞菁钴和酞菁铁作为对比, 研究了双核钴锰酞菁在1.5 mol·L-1 LiAlCl4/SOCl2电解液中的电催化行为, 并计算出动力学参数, 由此来评估具有平面结构的双核金属酞菁化合物对亚硫酰氯还原的催化活性的影响. 通过比较循环伏安曲线发现, 与单核酞菁钴(II)和酞菁铁(II)相比, 双核钴锰酞菁对SOCl2还原反应具有更好的催化活性, 能提高SOCl2还原反应的交换速率常数和SOCl2在玻碳电极上的扩散系数, 从而提高SOCl2还原电位和电流.通过ER14250型实体电池10 mA放电性能测试验证表明, 与单核酞菁钴和酞菁铁催化剂的电池相比, 双核钴锰酞菁在低温(-30 ℃)下可提高放电中点电压0.3 V, 在常温(25 ℃)下可以提高放电容量约100 mAh, 催化效果比单核酞菁钴和酞菁铁显著.     

Electrocatalytic activity of cobalt phthalocyanine CoPc adsorbed on a graphite electrode for the oxidation of reduced L-glutathione (GSH) and the reduction of its disulfide (GSSG) at physiological pH

Modified electrodes coated by adsorbed cobalt phthalocyanines are known to show substantial electrocatalytic activity for the electro-oxidation of several thiols in alkaline aqueous solution. In this context, we explore in this study the electrocatalytic activity of adsorbed cobalt phthalocyanine (CoPc) on ordinary pyrolytic graphite electrode for the oxidation of reduced L-glutathione GSH and the reduction of its disulfide GSSG at physiological pH. To do so, cyclic and rotating disk voltammetries were performed and the amperometric results show that a stable electrochemical sensing material, with good reproducibility and sensitivity (in accordance with the concentrations of GSH expected in biological media), can be easily achieved. This opens the way for the design of an electrochemical sensor able to detect these two analytes in biologically relevant experimental conditions (in terms of pH).     

Application of a Tetraamino Cobalt(II) Phthalocyanine Modified Screen Printed Carbon Electrode for the Sensitive Electrochemical Determination of L-Dopa in Pharmaceutical and Biological Samples

A novel synthesized tetraamino cobalt(II) phthalocyanine monomer was used for the fabrication of a sensor by electrochemical polymerization. A disposable electrochemical sensor based on the use of a screen printed carbon electrode covered with an electropolymerized film of tetraamino cobalt(II) phthalocyanine for the determination of L-dopa in pharmaceutical tablets and biological samples was described. Cyclic voltammetry and electrochemical impedance spectroscopy were performed for the characterization of the bare and modified electrode. For the electrochemical detection of L-dopa differential pulse voltammetry was used. The proposed method exhibits a good response towards electrooxidation of L-dopa in the linear concentration range: from 0.1 to 1000.0 μmol L⁻¹ in BRB pH=2.0, with a detection limit of 0.03 μmol L⁻¹ and from 1 to 1000 μmol L⁻¹ in PBS pH=7.4, with a detection limit of 0.33 μmol L⁻¹. Due to the fact that the developed sensor was applied in two different types of real samples, two buffer media were used, BRB pH=2.0 for pharmaceutical and urine samples and PBS pH=7.4 for whole blood samples. The proposed pCoTAPc/SPCE was successfully applied for the determination of L-dopa in pharmaceutical tablets, urine and in whole blood samples with satisfactory results.     

Performance of glucose electrooxidation on Ni–Co composition dispersed on the poly(isonicotinic acid) (SDS) film

Poly(isonicotinic acid) (PINA) film was electrosynthesized on carbon paste electrode (CPE) by using the repeated potential cycling technique in aqueous solution containing isonicotinic acid (INA), sulfuric acid and sodium dodecyl sulfate (SDS). Then, nickel and cobalt ions were incorporated by immersion of CPE/PINA prepared in the presence of SDS (CPE/PINA(SDS)) in a solution with different proportions of nickel chloride and cobalt chloride. The electrochemical characterization of mixed hydroxides containing cobalt and nickel at the surface of the modified electrode is presented. The modified electrodes were successfully used in the electrocatalytic oxidation of glucose. Finally, the electrocatalytic oxidation peak currents of glucose exhibited a good linear dependence on concentration, and its quantification can be done easily. The good analytical performance, low cost and straightforward preparation method make this novel electrode material promising for the development of an effective glucose sensor.     

Hybrid Materials from Carbon Nanotubes,Nickel Tetrasulfonated Phthalocyanine and Thin Polymer Layers for the Selective Electrochemical Activation of Nitric Oxide in Solution

The elaboration of hybrid materials from single‐wall carbon nanotubes (SWCNT) and tetrasulfonated nickel phthalocyanine (NiTSPc) was electrochemically performed to obtain chemically modified electrodes with improved electrocatalytic activity towards the electrooxidation of nitric oxide (NO). The characterization of these hybrid electrodes was achieved by cyclic voltammetry and AFM. The electrochemical performances of the electrodes towards the oxidation of NO were then analyzed by chronoamperometry and the obtained results show that the presence of SWCNT greatly enhances the electrocatalytic performances in terms of current intensity. Additional coatings were then electrodeposited over the hybrid electrodes to act as selective membranes against four major interfering analytes: nitrite, ascorbate, hydrogen peroxide and L ‐arginine. Several polymer coatings were tested to achieve the best balance between sensitivity to NO and selectivity against interferents.     

Electrochemical Detection of TNT at Cobalt Phthalocyanine Mediated Screen‐Printed Electrodes and Application to Detection of Airborne Vapours

We describe the use of cobalt phthalocyanine as a mediator to improve the sensitivity for the electrochemical detection of TNT. Commercial screen‐printed electrodes containing cobalt phthalocyanine were employed for determination of TNT. Improved sensitivities compared to screen‐printed carbon electrodes without phthalocyanine were observed, current response for cyclic voltammetric measurements at modified electrodes being at least double that of unmodified electrodes. A synergistic effect between oxygen and TNT reduction was also observed. Correlation between TNT concentrations and sensor output was observed between 0–200 µM TNT. Initial proof‐of‐concept experiments combining electrochemical determinations, with the use of an air‐sampling cyclone, are also reported.     

Degree of solid-phase oxidation of nickel and cobalt phthalocyanines by halogens

Electronic and IR transmission spectroscopy and ESR have been used to investigate the products obtained in the oxidation of layes of nickel and cobalt phthalocyanines by halogen vapors. It has been established that cobalt phthalocyanine in chlorine or bromine vapor forms stable cation radicals in which one electron has been detached from the cobalt and the other from the phthalocyanine ligand; in iodine vapor, a partially oxidized product is formed, with a positive charge on the ligand. Nickel phthalocyanine in bromine vapor at high pressure of bromine, and also in chlorine or iodine vapor, nickel phthalocyanine forms partially oxidized products with various degrees of oxidation of the ligand. An interpretation is given for the spectra of the ionic species that have been investigated; the interpretation can be used in particular to determine the degree of the ionic species on the basis of their spectra.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 5, pp. 528–534, September–October, 1989.The authors wish to thank A. V. Baranov for measuring the Raman spectrum of the bromine-oxidized Copc.     

Synthesis and Electrochemical and In Situ Spectroelectrochemical Characterization of Chloroindium(III) and Chloromanganese(III) Phthalocyanines Bearing 4‐((4′‐Trifluoromethyl)phenoxy)phenoxy Substituents

The synthesis of novel tetra‐substituted manganese and indium phthalocyanines was achieved by cyclotetramerization of corresponding phthalonitrile derivative. The new compounds have been characterized by using UV‐vis, IR, ¹H NMR and mass spectroscopic data. Spectroelectrochemical characterization of an indium phthalocyanine complex was performed for the first time in this paper and its electrochemical and spectroelectrochemical responses were compared with manganese phthalocyanine, bearing a redox active metal center. Electrochemical and spectroelectrochemical measurements exhibit that incorporation of redox active metal ion, Mn^III, instead of In^III into the phthalocyanine core extends the redox capabilities of the complex including the metal‐based reduction couples of the metal center and affect the aggregation behavior of the complexes. Presence of molecular oxygen in the electrolyte system affects the voltammetric and spectroelectrochemical responses of the phthalocyanines due to the interaction between the complexes and molecular oxygen. MnPc and InPc formed µ‐oxo species and this reaction changed the electrochemical and optic responses of the complexes, which are desired properties for sensor and electrocatalytic applications of a material. An in situ electrocolorimetric method has been applied to investigate the color of the electro‐generated anionic and cationic forms of the complexes for possible electrochromatic applications and for clarify the interaction mechanism of the MnPc with molecular oxygen.     

The Influence of the Synthesis Temperature on Cobalt Phthalocyanine Encapsulation in Zeolite Y

Several characterization techniques were applied to study the effect of the synthesis temperature on the physicochemical properties of cobalt phthalocyanine incoporated into zeolite Y. The cobalt phthalocyanine was synthesized in the supercages of zeolite Y by the template synthesis method at two different temperatures of 200 and300 °C and characterized by diffuse reflectance spectroscopy, Fourier transform infraredspectroscopy, pore volume analysis, unit cell dimension calculation, UV-vis spectroscopy,thermogravimetric analysis and X-ray diffraction. The results show that the catalyst synthesizedat 200 °C contains 11 wt.% cobalt phthalocyanine and almost all of thiscomplex is encapsulated in the supercages as monomeric species. At higher temperature aconsiderable amount of the cobalt phthalocyanine is hosted in the mesopores and/or on theexternal surface of the zeolite as aggregates. The migration of one part of the cobalt cationsfrom the supercages to the small cages at 300 °C decreases the formation of thenon-aggregated encapsulated phthalocyanine molecules in the zeolite supercages. Theaggregated cobalt phthalocyanine formed at the surface corresponds to the -polymorph stateof the phthalocyanine.     

Cobalt nanoparticles anchored to porous silicon as a novel modifier for the construction of enzyme‐free hydrogen peroxide screen‐printed sensor

In this work, a screen‐printed carbon electrode (SPCE) was modified with a cobalt/porous silicon (Co@PSi) nanocomposite powder to develop a nonenzymatic sensor for the detection of hydrogen peroxide. The Co@PSi nanocomposite was synthesized through the chemical reaction between silicon powder in a HF/HNO₃ solution and cobalt cations. In this process, cobalt nanoparticles were anchored on the porous silicon. The structure and morphology of the synthesized nanocomposite were investigated by X‐ray diffraction, Fourier transform infrared spectroscopy, X‐ray photoemission spectroscopy, energy dispersive X‐ray spectroscopy, and field‐emission scanning electron microscopy. The constructed nonenzymatic, screen‐printed sensors based on the Co@PSi nanocomposite showed perfect electrocatalytic oxidation response to hydrogen peroxide over the range 1–170 and 170–3,770 μmol/L with the limit of detection of 0.8 μmol/L. In addition, the Co@PSi‐SPCE sensor exhibited good selectivity for the determination of H₂O₂ in the presence of common interfering species including glucose, ascorbic acid, uric acid, dopamine, nitrate, and nitrite ions. The constructed electrochemical sensor was successfully used for the determination of H₂O₂ in real samples.     

乙醇对双核酞菁钴掺杂聚苯胺膜修饰电极特性的影响

研究了乙醇对双核酞菁钴(b i-CoPc)掺杂聚苯胺(PAn)膜修饰电极特性的影响。用循环伏安法(CV)考察了乙醇浓度不同时,玻碳电极(GC)上双核酞菁钴掺杂聚苯胺的电聚合过程,用紫外-可见吸收光谱(UV-V is)、红外光谱(FTIR)和扫描电子显微镜(SEM)表征了在氧化铟锡玻璃(ITO)电极上b i-CoPc掺杂的PAn膜,研究了乙醇对膜以及该膜修饰电极对溶液中分子氧电催化性能的影响。结果表明,乙醇对苯胺的电聚合有促进作用,有助于增加b i-CoPc掺杂量,膜的光谱特性发生变化,表面形貌更加均匀。乙醇存在下制备的修饰电极对溶液中分子氧的电催化活性明显提高。当乙醇含量为10%时,制备的电极催化能力最强。     

Effects of Substituents on the Electrocatalytic Activity of Cobalt Phthalocyanines when Conjugated to Graphene Quantum Dots

We report on the π–π interactions between graphene quantum dots (GQDs) and the following cobalt phthalocyanine derivatives: cobalt monocarboxyphenoxy phthalocyanine (complex 1 ), cobalt tetracarboxyphenoxyphthalocyanine (complex 2 ), and cobalt tetraaminophenoxy phthalocyanine (complex 3 ). The conjugates (conj) with GQDs are represented as 1 @GQDs(conj), 2 @GQDs(conj) and 3 @GQDs(conj), respectively. The resulting phthalocyanine/GQDs conjugates were adsorbed on containing a glassy carbon electrode (GCE) using the drop and dry method. We explore the electrochemical properties of phthalocyanines functionalized with both electron withdrawing groups and electron donating groups when non‐covalently linked to the π‐electron rich graphene quantum dots. GCE/ 3, GCE/ 2 @GQDs(conj) and GCE/ 1 @GQDs(conj) had the lowest limits of detection (LOD). Sequentially modified electrodes showed less favourable detection limits compared to the conjugates.     

Electrocatalytic Determination of Nitrite on a Rigid Disk Electrode Having Cobalt Phthalocyanine Prepared In Situ

This work reports an in situ cobalt(II) phthalocyanine (CoPc) synthesis on a SiO₂/SnO₂ (SiSn) matrix surface obtained by the sol‐gel method and its electrocatalytic activity for oxidation of nitrite. A rigid disk electrode with SiSn/CoPc was used to study the electrooxidation of nitrite by the cyclic voltammetric, chronoamperometric techniques and differential pulse voltammetry (DPV). The adsorbed phthalocyanine electrocatalyzed nitrite oxidation at 0.73 V (versus SCE) using the DPV technique. The anodic peak current intensities, plotted from differential pulse voltammograms in 1 mol L^?1 KCl for the concentration range 0.002 to 3.85 mmol L^?1 of nitrite were linear, with a correlation coefficient of 0.998 and a detection limit of 0.95 μmol L^?1.