Cobalt phthalocyanine-based conjugated polymer as efficient and exclusive electrocatalyst for CO_(2) reduction to ethanol

Electrocatalytic conversion of carbon dioxide to high value-added chemicals is a promising method for solving the energy crisis and global warming.Electrochemical active metal-containing conjugated polymers have been widely studied for heterogeneous carbon dioxide reduction.In the present contribution,we designed and synthesized a stable cobalt phthalocyanine-based conjugated polymer,named CoPPc-TFPPy-CP,and also explored its electro-catalytic application in carbon dioxide reduction to liquid products in an aqueous solution.In the catalyst,cobalt phthalocyanine acts as building blocks connected with 1,3,6,8-tetrakis(4-formyl phenyl)pyrenes via imine-linkages,leading to mesoporous formation polymers with the pore size centered at 4.1nm.And the central co-balt atoms shifted to a higher oxidation state after condensation.With these chemical and structural natures,the catalyst displayed a remarkable electrocatalytic CO_(2) reduction performance with an ethanol Faradaic efficiency of 43.25%at-1.0V vs RHE.While at the same time,the electrochemical reduction process catalyzed by cobalt phthalocyanine produced only carbon monoxide and hydrogen.To the best of our knowledge,CoPPc-TFPPy-CP is the first example among organic polymers and metal-organic frameworks that produces ethanol from CO_(2) with a remarkable selectivity.

Effect of Cobalt Phthalocyanine on Floating-Charge Performance of Nickel-Metal Hydride Battery

In Ni-MH battery, oxygen evolution causes a high inner pressure during charge and overdischarge, and an inappropriate eliminating way of the oxygen in the battery results in accumulation of heat. This is the main obstacle to develop and apply high capability and high power battery. In this paper, effect of cobalt phthalocyanine (CoPc) on the floating-charge performance of Ni-MH batteries are examined. Experimental results show that the battery with CoPc additive by appropriate adding way displayed a better capability of floating charge and discharge than the one without CoPc. The battery with CoPc added into electrolyte shows the best charging efficiency and cycleability and the slowest increasing speed of inner pressure after 2000th charge and discharge.

Didodecyldimethylammonium Bromide Films Containing Cobalt Phthalocyanine Tetrasulfonate for Electrochemical Catalysis

Electrochemistry of didodecyldimethylammonium (DDAB) films containing cobalt phthalocyanine tetrasulfonate (CoPcTS4-) was examined. CoPcTS4--DDAB film electrode showed stable cyclic voltammetric responses in buffers and could catalyze reductions of trichloroacetic acid.

Catalytic Decomposition of Chlorophenols Using Fiber-supported Cobalt Phthalocyanine

A novel heterogeneous catalyst, viscose fiber- supported cobalt phthalocyanine （Co - TDTAPc - F）, was prepared by immobilizing cobalt tetra（2.4 - dichloro- 1,3, 5 -triazine）aminophtbalocyanine （Co- TDTAPc） on viscose fibers covalcntly. The oxidative removal of chlorophenols such as 2 - chlorophenoi, 4 - chlorophenol, 2, 4 - dichlorophenol, and 2, 4, 6 - trichlorophenol was investigated in the catalytic oxidative system of Co - TDTAPc- F/H2O2. Furthermore, more than 98% of these chloropbenols were decomposed in 4 h. Phenol, oxalic acid, maleic acid, and succinic acid, etc., were detected by high performance liquid chromatography （HPLC） and gas chromatography-mass spectrophotometer （GC - MS）, and these short-chain organic acids could be further oxidized easily. The results indicated that the catalytic oxidation in the Co- TDTAPc - F/H2O2 system leaded to a deeper oxidation. In addition, a degradation pathway for chlorophenols was proposed on the basis of detection of intermediate compounds.

Constructing S-scheme charge separation in cobalt phthalocyanine/oxygen-doped g-C_(3)N_(4) heterojunction with enhanced photothermal-assisted photocatalytic H_(2) evolution

Hydrogen acquisition from solar energy is an effective way to address energy crisis,which makes the development of efficient photocatalysts become the main direction of scientific research.Herein,cobalt phthalocyanine/oxygen-doped g-C_(3)N_(4)(CoPc/OCN) S-scheme heterojunction photocatalyst was designed by coupling multi-step calcination with solvothermal method for enhanced photothermal-assisted photocatalytic H_(2) evolution.The multistep calcined g-C_(3)N_(4) is easier for O-doping formation,and the ethanol solvothermal strategy is utilized to enhance the dispersion of CoPc on OCN nano sheet surface and forms sufficient S-scheme heterojunction through H-bonds.In addition,the active sites and excellent photothermal properties of CoPc itself further improve the integrated photocatalytic activity of CoPc/OCN S-scheme heterojunction.The optimal photocatalytic hydrogen evolution rate of CoPc/OCN S-scheme heterojunction photocatalyst reached 9.56 mmol·g^(-1)·h^(-1),which is 2.69 and 1.23 times higher than that of CN and OCN,respectively.This work provides a valuable design idea and scheme for enhancing the multi-factor co-assisted photocatalytic H_(2) evolution performance.

“Substituents optimization”and“push effect”dual strategy for design of cobalt phthalocyanine catalyst on oxygen reduction reaction

Molecular metallocycle electrocatalysts like metalloporphyrins and metallophthalocyanines were found to be effective for oxygen reduction reaction(ORR)due to their M-N_(4) active sites and large conjugated elec-tronic molecular structures.Herein,the“substituents optimization”strategy combined with“push effect”modification was innovatively employed to target a single Co-N_(4) active site in three substituted phthalo-cyaninato cobalt complexes:tetranitrophthalocyaninato cobalt(CoTNPc),tetra(4-nitrophenoxy)phthalo-cyaninato cobalt(CoTPNPc),and tetraphenoxy phthalocyaninato cobalt(CoTPPc)electrocatalyst,also with 4-phenylpyridine axial coordination on Co-N_(4) unit.Through substituents screening,the half-wave poten-tial(E_(1/2))for ORR increases in the order of CoTPNPc(0.75 V)<CoTPPc(0.80 V)<CoTNPc(0.83 V)along with decreased electron-withdrawing ability of their substituents from-OC_(6) H_(4)-NO_(2),-OC_(6) H_(5) to-NO_(2) in the three cobalt phthalocyanine derivatives.CoTNPc with the weakest electron-withdrawing substituent exhibits the best ORR performance among the three compounds.This is attributed to its higher elec-tron delocalization and lifted HOMO energy level with the lower energy barrier in the rate-determining step relative to the other two compounds,which facilitate the electron transfer and reduction of oxy-gen as evidenced by XPS,UPS,and DRS analysis combined with DFT calculations.Further coordination of 4-phenylpyridine shifts the E_(1/2) up to 0.78,0.82,and 0.85 V for CoTPNPc,CoTPPc,and CoTNPc.DFT calcu-lations demonstrate that the introduction of the electron-donating phenylpyridine ligand into the cobalt phthalocyanines breaks the symmetry of the Co-N_(4) center and also raises the electron density of Co sites,which promotes O_(2) adsorption and improves ORR performance.After comparing the two strategies,the substituents on metallophthalocyanine are more determined by the electroactivity than the axial group,which directly regulates the coordination environment and then the activation barrier of the ORR pro-cess.This work provides theoretical and experimental guidance by two coupling strategies for the design of highly active molecular CoPc-based ORR electrocatalysts in the practical application.

Coordination engineering of cobalt phthalocyanine by functionalized carbon nanotube for efficient and highly stable carbon dioxide reduction at high current density

Coordination engineering can enhance the activity and stability of the catalyst in heterogeneous catalysis.However,the axial coordination engineering between different groups on the carbon carrier and molecular catalysts in the electrocatalytic carbon dioxide reduction reaction(CO_(2)RR)has been studied rarely.Through coordination engineering strategy,a series of amino(NH_(2)),hydroxyl(OH),and carboxyl(COOH)groups functionalized carbon nanotubes(CNT)immobilized cobalt phthalocyanine(CoPc)catalysts are designed.Compared with no groups,OH groups and COOH groups,NH_(2)groups can effectively change the coordination environment of the central metal Co,thereby significantly increasing the turnover frequency(TOF)(31.4 s^(-1)at-0.6 V vs.RHE,CoPc/NH_(2)-CNT>CoPc/OH-CNT>CoPc/COOH-CN>CoPc/CNT).In the flow cell,the CoPc/NH_(2)-CNT catalyst has high carbon monoxide(CO)selectivity at high current density(~100%at-225 mA·cm^(-2),~96%at-351 mA·cm^(-2)).Importantly,the CoPc/NH_(2)-CNT catalyst can operate stably for 100 h at 225 mA·cm^(-2).Theoretical calculations reveal that CoPc/NH_(2)-CNT catalyst is beneficial to the formation of^(*)COOH and desorption of^(*)CO,thus promoting CO_(2)RR.This work provides an excellent platform for understanding the effect of coordination engineering on electrocatalytic performance and promotes a way to explore efficient and stable catalysts in other applications.

Enhanced electrocatalytic oxidation of dyes in aqueous solution using cobalt phthalocyanine modified activated carbon fiber anode

Cobalt tetra（2,4-dichloro-1,3,5-triazine）aminophthalocyanine （CoPc） was immobilized covalently on activated carbon fiber （ACF） felt to obtain CoPc-modified ACF （CoPc-ACF） catalyst, and an electrocatalytic oxidation system using CoPc-ACF as the anode was constructed. The electrocatalytic oxidation of Acid Red 1 （ARI） was investigated in aqueous solution by an UV-vis spectrophotometer and UPLC. The results indicated that AR1 could be eliminated efficiently in this electrocatalytic oxidation system. In addition, the results of FTIR, TOC and GC-MS suggested that the electrocatalytic oxidation experienced the decoloration achieved by destroying the azo linkage and the further mineralization due to the cleavages of benzene ring and naphthalene ring. The intermediates were mainly small molecular compounds such as maleic acid and succinic acid, etc. Re- petitive tests showed that CoPc-ACF can maintain high electrocatalytic activity over several cycles. The further EPR spin-trap experiments indicated that the hydroxyl radicals did not dominate the reaction in this electrocatalytic system, which was com- pletely different from the traditional electro-Fenton system. Based on the non-radical reaction mechanism, the CoPc-modified ACF electrocatalyst has potential application in treating actual dyestuffs wastewaters, which are accompanied with high concentration of hydroxyl radical scavengers such as chlorine ions and additives in the textile printing and dyeing industry.

Cobalt‐N_(4) macrocyclic complexes for heterogeneous electrocatalysis of the CO_(2) reduction reaction

Metal-N_(4)(M-N_(4))macrocyclic complexes are interesting electrocatalysts due to their well-defined structures and rich molecular tuning.Among them,metal phthalocyanines have been widely studied for the carbon dioxide reduction reaction(CO_(2)RR)in heterogeneous systems and demonstrated good electrocatalytic performance.However,other complexes like metal corroles and metal porphyrins are much less explored,and often show inferior performances.In this study,three cobalt macrocyclic complexes,cobalt phthalocyanine,cobalt meso-tetraphenylporphyrin,and cobalt meso-triphenylcorrole(CoPc,CoTPP and CoTPC)are investigated in heterogeneous electrocatalysis of CO_(2)RR.Although CoPc/carbon nanotube(CNT)hybrid exhibits high electrocatalytic activity,CNT hybridization does not work for CoTPC and CoTPP that hold weak interactions with CNTs.By the drop-dry method with a high molecular loading of 5.4×10^(–7) mol cm^(–2),CoTPC and CoTPP could deliver appreciable electrode activities.Poly(4-vinylpyridine)(PVP)introduction is further demonstrated as a facile method to afford enhanced activities for CoTPP at low molecular loadings through enhancing molecule-substrate interactions.The partial current density of carbon monoxide for CoTPP+CNT/PVP is around 8 times higher than the sample without PVP at–0.67 V versus reversible hydrogen electrode.This work provides solutions to enhance the electrode activities of molecular electrocatalysts with weak substrate interactions in heterogeneous systems.

Multiscale engineering of molecular electrocatalysts for the rapid hydrogen evolution reaction

Molecular electrocatalysts have demonstrated potential for the hydrogen evolution reaction(HER)due to their well-defined structures and high intrinsic activities.Achieving rapid production of hydrogen requires molecular electrocatalysts to operate at high current densities,which still presents a challenge.In this work,we demonstrate that molecularly dispersed electrocatalysts of cobalt phthalocyanine anchored on carbon nanotubes(CoPc MDEs)are superior candidates due to the efficient charge transport between the substrate and the active site.The intrinsic activity can be enhanced by introducing functional groups on phthalocyanine.To facilitate mass transport,di(ethylene glycol)substituted CoPc molecules are further anchored on a threedimensional self-supported electrode(CoPc-DEG MDE@CC),enabling continuous operation for 25 h at−1000 mA/cm^(2)in 1.0 M KOH.Our study demonstrates the potential of molecular electrocatalysts for HER and emphasizes the importance of adjusting intrinsic activity,and charge and mass transport capacity for practical molecular electrocatalysts.

Electron-withdrawing functional ligand promotes CO2 reduction catalysis in single atom catalyst

Electrochemical carbon dioxide reduction reaction (CO2RR) powered by renewable electricity offers an attractive approach to reduce carbon emission and at the same time produce valuable chemicals/fuels.To design efficient CO2 reduction electrocatalyst,it is important to understand the structure-activity relationship.Herein,we design a series of single Co atoms electrocatalysts with well-defined active sites electronic structures,which exhibit outstanding CO2RR activity with controllable selectivity to CO.Experimental and density functional theory (DFT) calculation studies show that introducing nitro (amino) ligand next to single Co atom catalytic center with electron-withdrawing (electron-donating) capability favors (hinders) CO2 reduction catalysis.This work provides an in-depth understanding of how functional ligand affects the splitting of transition metal 3d electron orbital,thereby changing the electron transfer from transition metal active site to CO2,which is closely related to the Gibbs free energy of the rate-determining step (CO2+e^-+*→*CO2^-).

A polyoxometalate based electrochemical sensor for efficient detection of L-cysteine

L-cysteine(L-cys),as an important sulfur-containing amino acid,plays an indispensable role in biological systems.Too low and excessively high ratio of L-cys will cause harm to the function of human organs.Therefore,it is very necessary to develop efficient methods to detect it in multifarious samples.This paper has built an electrochemical sensor by combining Keggin-type polyoxometalate(PMo9V3)and cobalt tetrasulfonate(Ⅱ)phthalocyanine(CoTsPc)on indium tin oxide electrodes using the layer-level self-assembly technology for efficiently detection of L-cys.The assembly process and surface morphology of the modified electrode was characterized by ultraviolet–visible spectroscopy,X-ray photoelectron spectroscopy,scanning electron microscope,and atomic force microscopy.The conditions of electro-catalysed oxidation of L-cys were optimized by cyclic voltammetry,and the kinetic electrochemical parameters were also evaluated by electrochemical impedance spectra.Furthermore,the sensing performance of the modified electrode was explored using amperometry.The proposed electrochemical L-cys sensor was found to have superior sensing performance with a range of linear response of 2.5×10^(−7) to 1.7×10^(−4) mol·L^(−1) and 1.7×10^(−4) to 39.5×10^(−4) mol·L^(−1),the detection limit of 1.0×10^(−7) mol·L^(−1)(signal/noise=3),and satisfactory anti-interference ability.Consequently,the fabricated sensor has the potential to be applied in laboratory practices for L-cys deterimination in commercial drinks.