Electrochemical Template Synthesis Research Articles

Turning natural copper phthalocyanine into high-loading single-atom catalysts using an electrochemically-generated template and cationic substitution

Phthalocyanine (PC) has a unique N4-coordinated structure that offers an inherent advantage with respect to the accommodation of metal ions. This feature can help overcome the limitations of many single-atom electrocatalysts, i.e. low loading and poor stability. Here, we detail the development of a universal electrochemical template and a cationic substitution synthesis protocol for preparing various single-atom catalysts with high-loading (≌ 8.6 wt%) from commercial copper phthalocyanine (CuPC). Commercial CuPC is transformed into Cu NPs and vacant N4-sites are created during applied potential cycling. The generated vacant N4-sites, with strong negative charges, can take-up Pd2+ ions from a precursor solution to create single-atom catalysts with Pd high-loadings. The material’s structural transformation and cationic substitution mechanism were investigated by in situ X-ray absorption spectroscopy (XAS). We also demonstrate the viability of extending the proposed electrochemical template synthesis method to the development of other high-loading transition metal single-atom catalysts, e.g., Ni, Co, and Fe.

Electrochemical template synthesis of Ni–Cu bilayer hollow microtubes for green hydrogen production through electrocatalytic reforming of ethanol

This article is devoted to the investigation of the processes occurring at the synthesis of Ni–Cu hollow tubes (NC-HT) and their application as an electrocatalyst in the hydrogen evolution reaction from water-ethanol solution. The reactions at the electrochemical reduction of CuO to Cu and during the electrodeposition of nickel were investigated by chronopotentiometry. Depending on the thickness of the nickel layer, morphology (SEM) and chemical composition (EDX-mapping, XRD) of tubes, as well as electrocatalytic activity (CVA, ECSA, TOF, and stability tests) were studied. The synthesized materials have a structure with a high electrochemically active surface area (ECSA) from 1.38 to 3.50 m2g-1, which makes it possible to fulfill low activation overpotential values equal to −86 and −250 mV at 10 and 50 mAcm−2 after 100 cycles. The stability test results demonstrate the overpotential values −160, −183, −265 mV for NC-HT15, NC-HT30, and NC-HT60, respectively, after 24 h examinations.

Coaxial structures based on NiO/Ni@Carbon felt: Synthesis features, electrochemical behavior and application perspectives

• Coaxial structures of NiO/Ni@Carbon felt were produced by electrochemical template synthesis. • By varying the temperature conditions, materials with different electrochemical behavior were synthesized. • The best temperature conditions are proposed for the electrochemical template synthesis of NiO/Ni@Carbon felt. The coaxial structures of NiO/Ni@Carbon felt were synthesized via an electrochemical template approach followed by annealing at various temperatures and exposure. Comparison of synthesis conditions, morphology features, as well as the results of measurements of electrochemical performance, made it possible to classify the application of the material by the annealing degree of carbon template (R). At R < 0.05, the material shows electrocatalytic properties in reactions of water splitting (η HER = -230 mV and η OER = 175 mV at j = 20 mA·cm −2 ). At 0.05 < R < 0.7, the practical application of the material lies in the field of chemical current sources and supercapacitors as a precursor ( C m = 20–200F·g −1 ). Materials with higher values of R (R > 0.7) do not exhibit either electrocatalytic or capacitive properties and are the subject of further research and search for practical use.

Electrochemical template synthesis of copper hollow microtubes with dendritic surface and advanced HER performance

This study is devoted to the electrochemical template synthesis of Cu-based electrode materials for the efficient hydrogen evolution reaction (HER). Hollow copper tubes with an inner diameter of 23 μm and a wall thickness of 2.5 μm were synthesized by the three-step method: electrodeposition of copper on the carbon felt (template), annealing of the composite in the air toward copper oxides with hollow tube (HT) morphology, and their electrochemical post-reduction to copper HT with the dendritic surface. The electrocatalytic test of the resulting material showed that the overpotential of HER is 215 mV, and the Tafel slope is 177 mV/dec. The electrochemical active surface area of the copper HT increased almost 10 times – from 300 cm2 to 2850 cm2 – relative to the electrodeposited sample. The stability test of the electrode material confirmed its high activity within 24 h at a current density of 10 mA∙cm−2 and an overpotential of −280 mV.

Co-Ni Nanowires Arrays with Tunable Properties Obtained by Template Synthesis

Co-Ni nanowires arrays were obtained by electrochemical template synthesis in a polycarbonate track etched (PCTE) membrane. To diminish the effects of anomalous deposition observed in the Co-Ni system, the electrochemical deposition was performed from a solution containing nickel and cobalt in an atomic ratio of 3:1. Electrochemical deposition was performed at constant potentials E = -0.8, -0.9, -1.0, -1.1, -1.2 V vs Ag/AgCl for 15 min. The structures were characterized electrochemically via cyclic voltammetry, chronoamperometry, and charge stripping. Co-Ni nanowires were characterized by scanning electron microscopy (SEM/EDAX) to assess the morphology and the composition of the Co-Ni alloy nanowires at different deposition potentials. Electrochemical and structural analysis provided details of their deposition kinetics, structure, and morphology, which would be used to build nanowires array with controlled structure and composition.

Electrochemical Template Synthesis of Copper Nanotubes from Nitrate and Sulfate Electrolytes

A comparative study of the crystal structure of the ordered arrays of copper nanostructures prepared by the electrochemical synthesis method in polymer templates from solutions of nitrate and sulfate electrolytes was made. Changes in the phase composition, unit cell parameter, degree of crystallinity, and crystallite size depending on the electrolyte composition and synthesis conditions were investigated. It was shown that the addition of 10 g/L of ethanol as a surfactant to both the sulfate and nitrate electrolytes allows preparing monocomponent copper nanotubes with high degrees of crystallinity.

The electrochemical cathodic template synthesis of nickel hydroxide thin films for electrochromic devices: role of temperature

The influence of temperature on the synthesis of Ni(OH) 2 electrochromic films prepared using the cathodic template method has been investigated. The influence of deposition temperature on the morphology of nickel hydroxide films has been determined. By means of scanning electron and atomic-force microscopy, it has been established that surface morphology depends on deposition temperature. The flattest film surface corresponded to a deposition temperature of 30 °С, which indicated high optical properties. The maximum profile shift of films deposited at different temperatures was 400nM, while for the film deposited at 30 °С – 212 nM. By means of X-ray diffraction, it has been established that all films have crystal lattice similar to α-Ni(OH) 2 , with a high number of defects в . It also has been discovered that at a deposition temperature of 20–60 °С, a peak at 2q=16° appears on the diffraction pattern, the highest intensity of which corresponds to the process temperature of 30–40 °С. By means of cyclic voltamperometry and recording of transmittance changes, it has been demonstrated that nickel hydroxide film deposited at 30 °С has the best electrochemical and optical properties. A partial correlation between optical and electrochemical properties of films deposited at different temperatures has been noted.

Controlled template synthesis and properties of cobalt nanotubes

This study has been focused on the influence of the conditions of electrochemical template synthesis (i.e., potential difference and temperature of electrolyte solutions) on the structural and conductive properties of cobalt nanotubes. Polyethylene terephthalate track-etched membranes with a pore density of 1 × 109 ions/cm2 have been used as a template. Scanning electron microscopy, X-ray diffraction, and energy dispersive analysis have been used for a comprehensive elucidation of the dimensionality, chemical composition, and crystal structure of the synthesized samples. The optimum conditions for the synthesis of cobalt nanotubes with a minimum crystallographic anisotropy have been determined. It has been shown that controlling the synthesis conditions by changing electrolyte solution temperature and applied potential difference, one can vary the electrical and conductive properties of cobalt nanotube arrays, which have promising application in magnetic recording storage devices, high-precision magnetic field sensors, and optical devices.

Zirconia/Graphene Oxide Hybrid Micromotors for Selective Capture of Nerve Agents

Self-propelled zirconia-graphene/Pt hybrid tubular micromotors, prepared by electrochemical template synthesis, are used for both high-affinity capture and isolation of nerve agents. The simultaneous electrochemical deposition of zirconia and reduced graphene oxide leads to high surface area with a needle-like zirconia microstructure. The attractive surface properties of graphene sheets are used as growth directing template for the electrochemical synthesis of high surface area of zirconia nanostructures for effective and selective binding of organophosphate compounds. Such selective binding is dramatically enhanced by the rapid movement of the motors and the corresponding bubble-induced solution mixing. The greatly increased fluid transport leads to a 15-fold faster remediation compared to the use of the static counterpart structures. The unique material properties allow the convenient alkaline regeneration of the micromotor surface, improving the cost effectiveness of this methodology. The new strategy ...

Электрохимический синтез и кристаллическая структура упорядоченных массивов нанотрубок кобальта

In this paper, using the method of electrochemical template synthesis, ordered arrays of metallic nanostructures on the basis of cobalt with various dimensions (180-380 nm) were obtained. The diameter of Co-nanotubes was controlled by original polymer matrix, which provided to prepare arrays consisting of individually standing cobalt nanotubes. The crystal structure of the synthesized samples was studied by X-ray diffraction to determine cell parameters and crystallite size. Decrease of the conductive properties of Co - nanotubes can be explained by inhomogeneity of the crystallites formed during synthesis, because the growth rate of nanostructures directly affects the size of the crystallites.

Synthesis and characterization of nanorods for magnetic rotational spectroscopy

Magnetic rotational spectroscopy (MRS) with magnetic nanoprobes is a powerful method for in-situ characterization of minute amounts of complex fluids. In MRS, a uniformly rotating magnetic field rotates magnetic micro- or nano-probes in the liquid and one analyzes the features of the probe rotation to extract rheological parameters of liquids. Magnetic properties of nanoprobes must be well characterized and understood to make results reliable and reproducible. Ni and Co nanorods synthesized by electrochemical template synthesis in alumina membranes are discussed in applications to MRS. We employ alternating gradient field magnetometry, X-ray diffraction, and magnetic force microscopy to evaluate and compare properties of these nanorods and study their performance as the MRS probes. It is shown that nickel nanorods do not seem to violate any assumptions of the MRS rigid dipole theory, while cobalt nanorods do.

Electrochemical template synthesis of adherent polyaniline thin films with tubular structure

The synthesis of nano and microstructured thin polyaniline (PANI) films by a simple and very efficient template-assisted method is presented. This work shows the synthesis and characterization of acoustically rigid thin films structured at nanotubular shape by using methyl orange (MO) as a template-assisted system. The amount of the tubes can be easily controlled by the charge passed. The morphology for different films growth was characterized by field emission scanning electron microscopy (FESEM), Atomic force microscopy (AFM), and quartz crystal microbalance with dissipation mode (QCM-D). Raman spectroscopy results show important changes in the conformational PANI chain of the tubular material compare with a non-tubular one that provokes the increase of bipolarons population. This should be responsible by some changes in the electrochemical behavior of tubular film compared with the granular material, due to the higher conductivity when the emeraldine form starts to be formed.

Green electrochemical template synthesis of CoPt nanoparticles with tunable size, composition, and magnetism from microemulsions using an ionic liquid (bmimPF6).

Electrodeposition from microemulsions using ionic liquids is revealed as a green method for synthesizing magnetic alloyed nanoparticles, avoiding the use of aggressive reducing agents. Microemulsions containing droplets of aqueous solution (electrolytic solution containing Pt(IV) and Co(II) ions) in an ionic liquid (bmimPF6) define nanoreactors in which the electrochemical reduction takes place. Highly crystalline hcp alloyed CoPt nanoparticles, in the 10-120 nm range with a rather narrow size distribution, have been deposited on a conductive substrate. The relative amount of aqueous solution to ionic liquid determines the size of the nanoreactors, which serve as nanotemplates for the growth of the nanoparticles and hence determine their size and distribution. Further, the stoichiometry (Pt(x)Co(1-x)) of the particles can be tuned by the composition of the electrolytic solution inside the droplets. The control of the size and composition of the particles allows tailoring the room-temperature magnetic behavior of the nanoparticles from superparaparamagnetic to hard magnetic (with a coercivity of HC = 4100 Oe) in the as-obtained state.

Electrochemical template synthesis of protein-imprinted magnetic polymer microrods

A novel method for the electrochemical template synthesis of surface-imprinted magnetic polymer microrods for protein recognition is proposed. The polymer was electrodeposited into sacrificial cylindrical microreactors, the internal walls of which were previously modified with a target model protein, avidin, by simple physisorption. The electropolymerization was performed from a mixture of 3,4-ethylenedioxythiophene, poly(styrenesulfonate) (PSS), and PSS-coated superparamagnetic nanoparticles resulting in the formation of inherently electroconductive polymers confined to the volume of the microreactor. Here we show that: (i) the template synthesis within cylindrical microreactors results in polymer rods with dimensions matching that of the reactor, (ii) the incorporation of superparamagnetic particles induces magnetic properties that allow for efficient collection and manipulation of the microrods released from the microreactors in magnetic field even from dilute solution, and (iii) the protein coating on the internal walls of the microreactors is shown to generate molecular imprints on the surface of the polymeric rods. This latter property was demonstrated by comparative binding experiments of a fluorescent avidin derivative to the surface-imprinted and non-imprinted magnetic polymer microrods.

Electrochemical synthesis of gold nanorods in track-etched polycarbonate membrane using removable mercury cathode

The electrochemical template synthesis of gold nanorods within the cylindrical pores of track- etched polycarbonate (PC) membrane using a remov- able mercury cathode is reported. The novelty of this new approach is that it eliminates the requirement of coating an approximately 500 nm-1 lm-thick metal- lic layer, as conducting substrate, onto one surface of the insulating template membrane by the sputter deposition technique. A two-compartment electro- chemical cell was designed and used for this work. The PC membrane was placed between the two compartments separating the aqueous solution of HAuCl4 from mercury. Mercury, filled in one of the compartments, is in contact with one surface of the membrane (similar to sputter-deposited metallic layer) and serves as the conducting substrate/cathode for the electrochemical deposition of gold in the nanopores of track-etched PC membrane. Once the electrodeposit- ion is completed, the mercury and the HAuCl4 solution are removed from the compartments, and a malleable track-etched PC membrane embedded with free-standing gold nanorods is obtained. The ensemble of the metal nanorods grown in the template membrane is not attached to any conducting substrate, and gold nanorods can be freed from the template membrane after the dissolution. The Au-deposited PC membrane and free- standing Au nanorods were characterized by EDXRF, XRD, UV-Visible spectroscopy, AFM, and FEG-TEM. The EDXRF and XRD studies confirmed the deposition of the face-centered cubic phase of Au in the pores of the PC membrane. The TEM studies showed the formation of a cigar-shaped gold nanorod in the cylindrical pores of the PC membrane. The diameter of gold nanorods ranges from 100 to 200 nm. The new approach is simple, cost- effective, and saves time.

Influence of an Au capping layer on the magnetic properties of CoPt nanowires

Equiatomic CoPt nanowires with a gold cap layer have been fabricated by electrochemical template synthesis. Au improves the structural and magnetic properties of the L10 ordered CoPt, leading to coercivities of up to 1.43 T. The anisotropy constant K1 was estimated as 3.9(9) MJ m−3 from the approach to saturation, and four effective anisotropy constants were determined from analysis of torque curves in a 14 T field. Multisegmented magnetic nanowires are produced using gold interlayers.

Using the Hard Templating Method for the Synthesis of Metal-Conducting Polymer Multi-Segmented Nanowires

With the development of nanotechnology, there is a growing demand for advanced electronics based on functional nanomaterials. In this respect, owing to their unique properties, conducting polymers (CP) synthesized in the form of one-dimensional (1D) nanostructures are of particular interest. In this feature paper, we first report one of the most powerful techniques, the hard templating synthesis, for elaborating a large number of uniform 1D CP nanotubes or nanowires with precise control over lengths and diameters. Then, recent advances in the preparation, through electrochemical template synthesis, of various multi-segmented nanowires containing a combination of metallic and polymeric components are discussed. Hybrid metal-CP nanowires are promising high tech materials as they exhibit enhanced performances compared to their bulk counterparts and are of direct interest for developing novel multifunctional systems for a wide range of applications. Finally, some future directions for research in the area of multi-segmented nanowires are proposed.

Electrosynthesized Surface‐Imprinted Conducting Polymer Microrods for Selective Protein Recognition

Novel surface-imprinted conducting polymer microrods are shown to selectively recognize the template protein, as demonstrated by competitive binding assays using fluorescence detection. The electrochemical template synthesis provides means for controlled fabrication and spatial confinement of the PEDOT/PSS polymer proposed in this work, which exhibits extraordinary low nonspecific interactions and is effectively turned into a selective protein sorbent upon imprinting.

Electrochemical template synthesis of large-scale uniform copper selenides nanowire arrays

Ordered Cu 3Se 2 nanowire arrays have been prepared by electrochemical template synthesis based on anodic alumina membranes at room temperature. After annealing in argon ambient at 300 °C for 1 h, Cu 2Se nanowire arrays were obtained by structural change. Field emission scanning electron microscopy (FE-SEM), x-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and selected-area electron diffraction (SAED) results show that single crystal copper selenides nanowires with a high filling rate are dense, smooth, and uniform in large area. The effects of several electrodeposition parameters on high-filling, stoichiometric and single crystal copper selenides were discussed.

Enhanced Sensitivity of a Glucose Sensor Adopting Polymer Microtubule

Sensitivity of a glucose biosensor based on conducting polymer micro-tubule was enhanced by introducing a Pt transducer layer. Electrochemical template synthesis using polycarbonate membrane was used to fabricate the micro tubule. Glucose oxidase from Aspergillus Niger was caged into the micro tubule structure by capping the mouth of the tubule with a nano porous polycarbonate membrane. This capped tubule structure worked as a cell-array retaining enzyme inside and as a sensing current collector for the electrochemical reaction of the species retained inside simultaneously. The nano pores of the capping membrane were filled with poly (1,3-phenylenediamine) by using electrochemical polymerization. Introducing a Pt transducer layer at the bottom side of the template enhanced the sensitivity of the sensor about sixty times compared to the one having Au layer. The larger the pore size of the template was, the faster was the response and the higher was the detection current because of the faster material transport into and out of the cells.