Influence Of The Electrical Parameters On The Fabrication Of Copper Nanowires Into Anodic Alumina Templates

Metallic copper nanowires have been grown into the pores of alumina membranes by electrodeposition from an aqueous solution containing CuSO4 .and H3BO3 at pH 3. In order to study the influence of the electrical parameters on growth and structure of nanowires, different deposition potentials (both in the region where hydrogen evolution reaction is allowed or not) and voltage perturbation modes (constant potential or unipolar pulsed depositions) were applied. In all cases, pure polycrystalline Cu nanowires were fabricated into template pores, having lengths increasing with the total deposition time. These nanowires were self-standing, because they retain their vertical orientation and parallel geometry even after total template dissolution. However, the electrical parameters influence the growth rate, length uniformity and crystal size of the nanowires. Continuous electrodeposition resulted in higher growth rates but less uniform lengths of nanowires grown inside different membrane pores, whilst a square pulse deposition produced a slower growth but quite uniform lengths. Also the grain size, of the order of 50 nm, was slightly influenced by the potential perturbation mode

Lead Nanowires for Microaccumulators Obtained Through Indirect Electrochemical Template Deposition

Metallic lead nanowires were deposited within pores of commercial anodic alumina membranes having an average pore diameter of 210 nm. “Direct” electrodeposition was attempted from 0.1 M Pb NO3 2 aqueous solution with a variable concentration of H3BO3 as a chelating agent, but it gave unsatisfactory results. An “indirect” two-step deposition procedure was then adopted, consisting of the anodic electrodeposition of -PbO2 nanowires, followed by their in situ reduction to metallic lead. Both these processes occurred at a high rate so that the indirect method led to a complete template pore filling with pure polycrystalline Pb in short times and with a high current efficiency

Fabrication and Photoelectrochemical Behavior of Ordered CIGS Nanowire Arrays for Application in Solar Cells

In this work, we report some preliminary results concerning the fabrication of quaternary copper, indium, gallium, and selenium CIGS nanowires that were grown inside the channels of an anodic alumina membrane by one-step potentiostatic deposition at different applied potentials and room temperature. A tunable nanowire composition was achieved through a manipulation of the applied potential and electrolyte composition. X-ray diffraction analysis showed that nanowires, whose chemical composition was determined by energy-dispersive spectroscopy analysis, were amorphous. A composition of Cu0.203In0.153Ga0.131Se0.513, very close to the stoichiometric value, was obtained. These nanostructures were also characterized by photoelectrochemical measurements: They showed a cathodic photocurrent and an optical gap of 1.55 eV

Electrochemical deposition of CZTS thin films on flexible substrate

Solar cells based on semiconductor thin films are emerging as alternative to silicon;however,the materials giving the highest efficiency,CdTe and CuInGaSe,contain toxic (Cd) and rare (In) elements.In this field,the challenge is to substitute In and Cd with abundant and non-toxic elements without lowering the high efficiency achieved with these technologies.Compounds based on copper,zinc,tin and sulfur (CZTS) are potentially promising materials,because they present all the above listed features.Among the different methods to obtain CZTS,the electrochemical route appears of great interest because easy to conduct.Up to date,the literature shows that non-uniformity in composition and/or the presence of secondary phases prevent the obtainment of electrochemical CZTS thin-film of high quality.In this paper,we present the principal results of an extensive investigations conducted in order to find suitable conditions for growing CZTS thin films with good performance through the simultaneous electrodeposition of elements having different standard electrochemical potentials.Thin films were obtained on a flexible substrate by potentiostatic deposition from aqueous baths by changing different deposition parameters (bath composition and temperature,deposition time).Chemical composition and structure of the electrodeposited films were evaluated by EDS,SEM,RAMAN and XRD.Preliminary results on the photoelectrochemical behaviour of the films will be also presented

One-Step Electrodeposition of CZTS for Solar Cell Absorber Layer

CZTS thin films were obtained by one-step electrochemical deposition from aqueous solution at room temperature. Films were deposited on two different substrates, ITO on PET, and electropolished Mo. Differently from previous studies focusing exclusively on the formation of kesterite (Cu4ZnSnS4), here, the synthesis of a phase with this exact composition was not considered as the unique objective. Really, starting from different baths, amorphous semiconducting layers containing copper–zinc–tin–sulphur with atomic fraction Cu0.592Zn0.124Sn0.063S0.221 and Cu0.415Zn0.061Sn0.349S0.175, were potentiostatically deposited. Due to the amorphous nature, it was not possible to detect if one or more phases were formed. By photoelectrochemical measurements, we evaluated optical gap values between 1.5 eV, similar to that assigned to kesterite, and 1.0 eV. Reproducibility and adhesion to the substrate were solved by changing S with Se. Preliminary results showed that an amorphous p-type layer, having atomic fraction Cu0.434Zn0.036Sn0.138Se0.392 and an optical gap of 1.33 eV, can be obtained by one-step electrochemical deposition

Electrodeposition from molybdate aqueous solutions: a preliminary study

The electrochemistry of molybdenum (Mo) and its oxides is very important for several applications in electrocatalysis,batteries,sensors and in particular for CIGS-based solar cells,where metal Mo is used as back contact.Properties and the fabrication method of Mo films are of fundamental importance,because they could induce significant changes in solar cell performances.The most important issues in the electrochemical behaviour of Mo are the nature and stability of its surface oxides,which are strongly dependent on deposition bath pH.Ivanova et al. (2006) reported that it is possible to accomplish the cathodic reduction of molybdate ions to metallic Mo from electrolytes containing HF.The addition of this acid selectively prevents the polymerization of MoO42- anions,therefore its concentration plays a fundamental role.A hard drawback connected to deposition in acid media is the strong hydrogen evolution,since H+ reduction is the reaction thermodynamically favoured,therefore it is necessary to apply a very high current density for appreciably depositing Mo.In this work,we report some preliminary results dealing with the electrodeposition process from molybdate aqueous solutions to grow thin films on different substrates and nanowires inside the channels of polycarbonate membranes;electrolyte pH was varied in order to evidence its role on the nature of the deposits,which were characterized by EDS,SEM,RAMAN and XRD analyses

Nanostructured electrochemical devices for sensing, energy conversion and storage

Nanostructured materials are attracting growing interest for improving performance of devices and systems of large technological interest. In this work, the principal results about the use of nanostructured materials in the field of electrochemical energy storage, electrochemical water splitting, and electrochemical sensing are presented. Nanostructures were fabricated with two different techniques. One of these was the electrodeposition of the desired material inside the channels of a porous support acting as template. The other one was based on displacement reaction induced by galvanic contact between metals with different electrochemical nobility. In the present work, a commercial polycarbonate membrane was used as template. In the field of the electrochemical energy storage, the attention was focused on lead-acid battery, and it has been found that nanostructured morphology enhances the active mass utilization up to about 80%, with consequent increase of specific energy and cycling rates to unattainable values for the commercial battery. Nanostructured Ni-IrO2 composite electrodes showed valuable catalytic activity for water oxidation. By comparison with other Ni-based electrocatalyst, this electrode appears as the most promising anode for electrochemical water splitting in alkaline cells. Also in the field of sensing, the nanostructured materials fabricated by displacement reaction showed performance of high interest. Some new results about the use of copper nanowires for H2O22 sensing will be showed, evidencing better performance in comparison with copper thin film. In this work, we will show that nanostructured electrodes are very promising candidate to form different electrochemical setups that operate more efficiently comparing to device with flat electrode materials

Flexible electrode based on gold nanoparticles and reduced graphene oxide for uric acid detection using linear sweep voltammetry

In this work, an electrochemical sensor for uric acid determination is shown with a preliminary study for its validation in real samples (milk and urine). Uric acid can be electrochemically oxidized in aqueous solutions and thus it is possible to obtain electrochemical sensors for this chemical by means of this electrooxidation reaction. Indium tin oxide coated on flexible polyethylene terephthalate substrate, modified with reduced graphene oxide and gold nanoparticles by co-electrodeposition, was used. Electrodeposition was performed at -0.8V vs SCE for 200 s. All samples were characterized by electron scan microscopy and electron diffraction spectroscopy. A careful investigation on the effect of pH was performed to understand its influence on uric acid oxidation. The detection of uric acid was using the linear sweep voltammetry. Results show that the peak current increases linearly with uric acid concentration from 10 to 1000 μM with a limit of detection of about 7.1 μM. The sensor shows high selectivity towards different interferents that can be found in the milk and urine matrix, such as chloride, calcium, sodium and ammonium ions. To prove the applicability of the proposed sensor, uric acid was quantified in real milk and urine samples with excellent results comparable to those of conventional techniques