Polymeric Cobalt Phthalocyanine Research Articles

Two-dimensional polymeric cobalt phthalocyanine synthesized by microwave irradiation and its use for continuous glucose monitoring

Two-dimensional polymeric cobalt phthalocyanine synthesized by microwave irradiation and its use for continuous glucose monitoring

Polymeric cobalt phthalocyanine on nickel foam as an efficient electrocatalyst for oxygen evolution reaction

Renewable energy is of prime importance for sustainable development. Hydrogen is considered as clean as well as an efficient energy source. In addition to H2 as fuel, polymer electrolyte membrane fuel cell requires oxygen as an oxidant. Electrocatalytic or photocatalytic water splitting processes yield H2 and O2. Compared to hydrogen evolution reaction (HER), the oxygen evolution reaction (OER) in water electrolysis is a very sluggish and slow process. Even precious and costly catalysts have demonstrated higher overpotential for OER. To overcome the issues related to overpotential as well as cost and durability, bio-inspired macrocycles and polymers based on phthalocyanine are being explored extensively because of their unique and versatile properties. In this effort, a novel cobalt phthalocyanine polymer (poly-CoTPzPyCPc) was synthesised and employed as a low-cost and efficient organic-based catalyst for OER. The characterized polymeric catalyst was coated on Ni foam and the fabricated electrodes were evaluated for OER in 0.1 M KOH. The electrodes Ni-foam, Ni/poly-CoTPzPyCPc, Ni/IrO2, and Ni/poly-CoTPzPyCPc + IrO2 exhibited an onset potential for OER at 1.57, 1.53, 1.47 and 1.43 V Vs. RHE, respectively. The Ni/poly-CoTPzPyCPc exhibited an overpotential of 365 mV (±2 mV) at a current density of 10 mA cm−2. Furthermore, the composite of poly-CoTPzPyCPc with IrO2, displayed surprisingly superior OER activity. The composite achieved a current density of 10 mA cm−2 at lower overpotential of 274 mV (±2 mV) than the polymeric phthalocyanine and benchmark IrO2 catalyst which showed an overpotential of 324 mV at the same current density. The Tafel slope value was found to be 89, 67, 34 and 31 mV/dec for pure Ni foam, Ni/poly-CoTPzPyCPc, Ni/IrO2 and Ni/poly-CoTPzPyCPc + IrO2, respectively. The stability studies performed on poly-CoTPzPyCPc + IrO2 composite catalyst revealed that the proposed catalyst is stable and can be successfully employed for OER in water electrolysis. The developed composite catalyst has a small amount loading of precious catalyst with simple organic based catalyst to achieve efficiency better than benchmark catalyst for OER.

In situ preparation of polymeric cobalt phthalocyanine–decorated TiO2 nanorods for efficient photocatalytic CO2 reduction

The integration of photosensitizers with low-cost and non-toxic metal oxides is a promising strategy to design heterogeneous photocatalysts for CO2 reduction. Herein, p–n heterojunction photocatalysts (T-CoPPcs) consisting of p-type polymeric cobalt phthalocyanines (CoPPcs) as a photosensitizer coupled with n-type TiO2 nanorods were fabricated through a facile, eco-friendly, one-pot hydrothermal reaction. In this process, CoPPcs were grown on n-type TiO2 nanorods, whereas protonated titanate nanorods began converting to the highly crystalline anatase phase with small crystals on the TiO2 surfaces. The introduction of CoPPcs not only improved the solar light utilization but also accelerated the separation and migration of charge carriers via the p–n heterojunction with the strong interfacial contact Ti–O–Co bond. The increases in crystallinity and surface area of TiO2 nanorods also contributed to the enhanced photoactivities of T-CoPPcs. The CO2 photoreduction of the synthesized materials was evaluated in CO2-saturated MeCN/water using [Co(bpy)3]2+ as a cocatalyst and triethanolamine as a hole scavenger. The optimized nanocomposite exhibited a remarkable CO generation rate of 4.42 mmol/h/g with a high selectivity of 85.3% and outstanding catalytic stability. The influences of cocatalyst concentration, water content, catalyst loading, and hole scavenger concentration were optimized for efficient CO2 reduction. The photocatalytic CO2 conversion efficiency of the present system is found to be higher than that of TiO2-based materials reported in the literature. We believe that this research into a heterostructural design strategy and photocatalytic system may be an inspiration for the development of photocatalytic CO2-to-CO conversion.

Edge-Functionalized Polyphthalocyanine Networks with High Oxygen Reduction Reaction Activity.

Two-dimensional (2D) conjugated aromatic networks (CAN) have been fabricated by ball milling of polymeric cobalt phthalocyanine precursors edge-functionalized with different aromatic acid anhydride substituents. The optimal CAN, obtained by using tetraphenylphthalic anhydride, consists of uniform and thin (2.9 nm) layers with a high BET surface (92 m2 g-1), resulting in well-defined Co-N4 active sites with a high degree of exposure. Thence, this material exhibits excellent electrocatalytic oxygen reduction reaction (44 mA mgcat.-1). Compared to a benchmark Pt/C catalyst, this value denotes 1.2- and 6.0-fold enhancements, respectively, in terms of the mass of Pt and total Pt/C. When utilized as air electrode catalysts in Zn-air batteries, this material provides a maximum areal power density (137 mW cm-2) and mass power density (0.68 W mgcat.-1), values which also clearly surpass those of benchmark Pt/C catalyst. This support-free and pyrolysis-free strategy developed in this work delivers a novel route for the applications of 2D materials in clean energy conversion and storage.

Mannich reaction derived phthalocyanine polymer for electrochemical detection of salicylic acid

The Mannich base derived polymeric cobalt phthalocyanine poly(CoTAPOPMPPc) was synthesized via three steps viz., i) formation of Mannich base, ii) conversion of Mannich base to oxy bridged phthalonitrile ligand and iii) the cyclotetramerization of oxy bridged phthalonitrile ligand to form polymeric phthalocyanine. The synthesized compounds were in pure state and have been characterized using various physicochemical and analytical techniques. The synthesized polymeric phthalocyanine poly(CoTAPOPMPPc) was immobilized on the glassy carbon electrode and characterised. The carbon nanoparticles (KB) were used for the fabrication of composite electrode GCE/KB-poly(CoTAPOPMPPc) and employed for the detection of salicylic acid (SA) using voltammetry and differential pulse voltametry (DPV). DPV peaks were well-resolved than the peaks observed in the CV. The DPV technique displayed linear response in the range 5–120 μM with limit of detection (LOD) 2 and 1.5 μM and sensitivity 0.0690 and 5.9957 μA μM−1 cm−2 at GCE/poly(CoTAPOPMPPc) and GCE/KB-poly(CoTAPOPMPPc), respectively. The chronoamperometry showed linear range between 0.5 and 4.5 μM salicylic acid with LOD of 0.18 and 0.12 μM with sensitivity of 1.7788 and 8.8245 μA μM−1 cm−2 at GCE/poly(CoTAPOPMPPc) and GCE/KB-poly(CoTAPOPMPPc) electrodes respectively. In addition to better electrocatalytic response for salicylic acid, GCE/KB-poly(CoTAPOPMPPc) did not show response for co-existing molecules inferring a selective response for salicylic acid. The proposed sensor demonstrated better sensing parameters and could be applied in the real sample analysis of SA.

A Precious‐Metal‐Free Hybrid Electrolyzer for Alcohol Oxidation Coupled to CO2‐to‐Syngas Conversion

AbstractElectrolyzers combining CO2 reduction (CO2R) with organic substrate oxidation can produce fuel and chemical feedstocks with a relatively low energy requirement when compared to systems that source electrons from water oxidation. Here, we report an anodic hybrid assembly based on a (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) electrocatalyst modified with a silatrane‐anchor (STEMPO), which is covalently immobilized on a mesoporous indium tin oxide (mesoITO) scaffold for efficient alcohol oxidation (AlcOx). This molecular anode was subsequently combined with a cathode consisting of a polymeric cobalt phthalocyanine on carbon nanotubes to construct a hybrid, precious‐metal‐free coupled AlcOx–CO2R electrolyzer. After three‐hour electrolysis, glycerol is selectively oxidized to glyceraldehyde with a turnover number (TON) of ≈1000 and Faradaic efficiency (FE) of 83 %. The cathode generated a stoichiometric amount of syngas with a CO:H2 ratio of 1.25±0.25 and an overall cobalt‐based TON of 894 with a FE of 82 %. This prototype device inspires the design and implementation of nonconventional strategies for coupling CO2R to less energy demanding, and value‐added, oxidative chemistry.

A Precious-Metal-Free Hybrid Electrolyzer for Alcohol Oxidation Coupled to CO2 -to-Syngas Conversion.

Electrolyzers combining CO2 reduction (CO2R) with organic substrate oxidation can produce fuel and chemical feedstocks with a relatively low energy requirement when compared to systems that source electrons from water oxidation. Here, we report an anodic hybrid assembly based on a (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) electrocatalyst modified with a silatrane‐anchor (STEMPO), which is covalently immobilized on a mesoporous indium tin oxide (mesoITO) scaffold for efficient alcohol oxidation (AlcOx). This molecular anode was subsequently combined with a cathode consisting of a polymeric cobalt phthalocyanine on carbon nanotubes to construct a hybrid, precious‐metal‐free coupled AlcOx–CO2R electrolyzer. After three‐hour electrolysis, glycerol is selectively oxidized to glyceraldehyde with a turnover number (TON) of ≈1000 and Faradaic efficiency (FE) of 83 %. The cathode generated a stoichiometric amount of syngas with a CO:H2 ratio of 1.25±0.25 and an overall cobalt‐based TON of 894 with a FE of 82 %. This prototype device inspires the design and implementation of nonconventional strategies for coupling CO2R to less energy demanding, and value‐added, oxidative chemistry.

π-Conjugated polymeric phthalocyanine for the oxidative coupling of amines.

A cross-linked π-conjugated polymeric cobalt phthalocyanine material was developed by a facile, economical, scalable, and solid-phase synthesis method. In addition to being highly recyclable, this material showed greatly enhanced activity for the aerobic oxidative coupling of amines compared with a molecular catalyst before heterogenization, indicating good prospects for the material with a π-conjugated electronic character.

Visible-Light-Driven CO2 Reduction by Mesoporous Carbon Nitride Modified with Polymeric Cobalt Phthalocyanine.

The integration of molecular catalysts with low‐cost, solid light absorbers presents a promising strategy to construct catalysts for the generation of solar fuels. Here, we report a photocatalyst for CO2 reduction that consists of a polymeric cobalt phthalocyanine catalyst (CoPPc) coupled with mesoporous carbon nitride (mpg‐CNx) as the photosensitizer. This precious‐metal‐free hybrid catalyst selectively converts CO2 to CO in organic solvents under UV/Vis light (AM 1.5G, 100 mW cm−2, λ>300 nm) with a cobalt‐based turnover number of 90 for CO after 60 h. Notably, the photocatalyst retains 60 % CO evolution activity under visible light irradiation (λ>400 nm) and displays moderate water tolerance. The in situ polymerization of the phthalocyanine allows control of catalyst loading and is key for achieving photocatalytic CO2 conversion.

Visible‐Light‐Driven CO2 Reduction by Mesoporous Carbon Nitride Modified with Polymeric Cobalt Phthalocyanine

AbstractThe integration of molecular catalysts with low‐cost, solid light absorbers presents a promising strategy to construct catalysts for the generation of solar fuels. Here, we report a photocatalyst for CO2 reduction that consists of a polymeric cobalt phthalocyanine catalyst (CoPPc) coupled with mesoporous carbon nitride (mpg‐CNx) as the photosensitizer. This precious‐metal‐free hybrid catalyst selectively converts CO2 to CO in organic solvents under UV/Vis light (AM 1.5G, 100 mW cm−2, λ>300 nm) with a cobalt‐based turnover number of 90 for CO after 60 h. Notably, the photocatalyst retains 60 % CO evolution activity under visible light irradiation (λ>400 nm) and displays moderate water tolerance. The in situ polymerization of the phthalocyanine allows control of catalyst loading and is key for achieving photocatalytic CO2 conversion.

Defect Engineering in Polymeric Cobalt Phthalocyanine Networks for Enhanced Electrochemical CO2 Reduction

AbstractThe electrochemical reduction of CO2 into fuels and valuable chemicals represents an appealing approach to alleviate energy crisis and global warming. Due to its sluggish reaction kinetics and the lack of suitable electrocatalysts it remains a major challenge. In this work, we report a facile synthetic approach to engineer a polymeric cobalt phthalocyanine network with rich defects for significantly enhanced electrocatalytic activity for CO2 reduction. The successful defect engineering not only promotes the formation of a stronger binding surface towards CO2, but also simultaneously turns the electronic character of the resulting cobalt phthalocyanine framework. As a result, the new defective polymer exhibits highly selective catalysis of aqueous reduction of CO2 into CO with a large faradaic efficiency of ca. 97 %, low applied overpotential of 490 mV (versus a reversible hydrogen electrode) and long‐term stability. We anticipated that this new strategy could inspire the discovery of new organic frameworks for efficient CO2 reduction, such as those (defective MOFs, COFs etc.), evidently advancing the development of catalysts for the CO2 reduction reaction.

Fragmentation of Manganese Phthalocyanine Films by Laser Radiation

The study of MPc is motivated by the prospects of the creation of optoelectronic devices that operate in the visible light range. The combination of their physico-chemical and semiconducting properties makes them the promising material for cheap thermo-stable organic optoelectronic devices. In connection with this the question of degradation of macrocyclic phthalocyanine when exposed by harsh environments, in particular laser radiation, is very actual The studies of MPc's degradation under electron beam and pyrolysis is well Pyrolysis of polymeric cobalt phthalocyanine [ was carried out at 500 - 1000°C, the mass spectra were recorded across 0.6 - 3.6 minutes. The proposed mechanism of initial thermal degradation leads to the isoindole derivatives The paper presents results of a study of fragmentation of manganese phthalocyanine films that are in the condensed state on a solid surface by means of laser irradiation (λ=532 nm), i.e. in the spectral region of absorption

Single Layer of Polymeric Cobalt Phthalocyanine: Promising Low‐Cost and High‐Activity Nanocatalysts for CO Oxidation

The catalytic behavior of transition metals (Sc to Zn) combined in polymeric phthalocyanine (Pc) is investigated systematically by using first-principles calculations. The results indicate that CoPc exhibits the highest catalytic activity for CO oxidation at room temperature with low energy barriers. By exploring the two well-established mechanisms for CO oxidation with O2 , namely, the Langmuir-Hinshelwood (LH) and the Eley-Rideal (ER) mechanisms, it is found that the first step of CO oxidation catalyzed by CoPc is the LH mechanism (CO + O2 → CO2 + O) with energy barrier as low as 0.65 eV. The second step proceeds via both ER and LH mechanisms (CO + O → CO2 ) with small energy barriers of 0.10 and 0.12 eV, respectively. The electronic resonance among Co-3d, CO-2π*, and O2 -2π* orbitals is responsible for the high activity of CoPc. These results have significant implications for a novel avenue to fabricate organometallic sheet nanocatalysts for CO oxidation with low cost and high activity.

Electrochemical lithium storage of C/Co composite as an anode material for lithium ion batteries

A novel C/Co composite with Co nanoparticles embedded in carbon matrix is synthesized firstly by pyrolysis of polymeric cobalt phthalocyanine (PcCo) at 700°C in argon atmosphere. This composite is investigated as an anode material for lithium ion batteries, indicating high tap density and excellent electrochemical performance. The C/Co electrode can retain a higher reversible capacity of over 600mAhg−1 at a current of 50mAg−1 after 40cycles and shows better rate capability and less hysteresis in comparison to carbon not containing Co. The significant improvement is attributed to the Co nanoparticles grown in-situ reaction with catalytic activity and high electrical conductivity.

Selective Oxidation of Thiols to Disulfides at Polymeric Cobalt Phthalocyanine Chemically Modified Electrodes

Cysteine, glutathione, and several other aliphatic and aromatic thiols were exhaustively oxidized at chemically modified reticulated vitreous carbon containing a polymer coating of cobalt phthalocyanine (CoPC). Coulometric measurements indicated that, for all thiols examined, the electro‐oxidation was a one‐electron process. Subsequent end product analysis by high performance liquid chromatography, polarimetry, and nuclear magnetic resonance spectrometry confirmed that, for cysteine and glutathione, the corresponding disulfide species were formed very cleanly with no evidence of further oxidation to the sulfinic or sulfonic acid. The polymeric CoPC electrodes were compatible with a wide range of solvent and pH conditions. Unlike most conventional electrodes, which are rapidly passivated upon attempted oxidation of organosulfur compounds, the CoPC electrodes were extraordinarily durable, exhibiting turnover numbers of greater than 104 for each center with little or no loss of activity.

Electro-oxidation of hydrazine at electrodes modified with polymeric cobalt phthalocyanine

The electrocatalytic oxidation of hydrazine in basic solution at glassy carbon ( gc) electrodes modified with a thin layer of polymeric cobalt phthalocyanines is described. Cyclic voltammetry ( cv) in aqueous media yields a well-defined chemically irreversible anodic wave ( E p = −0.30 V vs. sce at pH 13), and peak currents for this process vary linearly with the square root of scan rate. Limiting currents measured at a rotating disk electrode are independent of the film thickness at a given substrate concentration; linear Levich plots are obtained under all experimental conditions used. Evaluation of the available data in light of the Savéant model for electrocatysis at polymer-modified electrodes suggests that the kinetics of the net 4e - -process is controlled by the diffusion of substrate from bulk solution to the solution/polymer interface.

Determination of 2‐thiothiazolidine‐4‐carboxylic acid in urine by liquid chromatography with electrochemical detection

AbstractAn assay procedure utilizing liquid chromatography and amperometric detection at a chemically modified electrode (CME) has been developed for the determination of 2‐thiothiazolidine‐4‐carboxylic acid (TTCA) in urine samples. The electrocatalytic activity of the CME, which consisted of a glassy carbon surface coated with an electropolymerized cobalt phthalocyanine film, permitted optimum response at a potential of +0.75 V vs. Ag/AgCl with a detection limit of 7 pmol for TTCA and with no sample preparation required. In case of fouling of the electrode surface by sample constituents, the polymeric cobalt phthalocyanine electrode surface could be renewed with a variability of less than 10% and an equilibration time of less than 15 minutes.

Electrocatalytic amperometric detection at polymeric cobalt phthalocyanine electrodes

AbstractGlassy carbon electrodes modified with a coating of a cobalt phthalocyanine containing polymer offer attractive features for applications as electrocatalytic amperometric sensors following liquid chromatography. These electrodes, which are formed by the anodic electropolymerization of Co‐4,4′,4″,4‴‐tetraaminophthalocyanine, exhibit electrocatalytic properties similar to those of earlier carbon paste electrodes containing Co phthalocyanine monomer added directly to the paste mixture. However, the polymer electrodes also offer increased stability and a compatibility with organic solvents not obtainable with the carbon paste version. The performance of the polymer electrodes is illustrated here for the detection of thiols following reversed‐phase liquid chromatography. Determination of picomole quantities of various thiols is possible at low positive potentials in mobile phases composed of 50% methanol or acetonitrile. Furthermore, the response of the electrodes is extremely stable, with more than 80% of the initial activity retained after 40 hours of continuous use.