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

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

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

Application of a Multiphase Interleaved DC-DC Converter for Power-To-Hydrogen Systems

Power electronics plays a crucial role in the implementation of a clean hydrogen production system, whose last stage consists of a water electrolyzer requiring a DC power supply to be in operation. The most recent architectural solutions imply the use of an isolated DC-DC converter, collecting energy from medium voltage (MV) and delivering it to the electrolyzer. An equivalent electrical model of the electrolyzer is therefore needed, as well as an accurate design of the power converter stage, aiming at a high-efficiency operation of the electrolyzer's cells and at a low-ripple supply current, to avoid premature degradation. This work investigates a full-bridge step-down isolated DC-DC converter, focusing on the opportunity of a multiphase interleaved configuration, particularly convenient for the proposed application. The considered maximum power level is 400 kW, representing a small-scale example of an industrial water electrolyzer supplied by a maximum DC voltage of 700 V. Input DC voltage is 7 kV. Power electronics' simulation have been carried out, as well as model analysis of the proposed converter

Anodic Alumina Membranes: From Electrochemical Growth to Use as Template for Fabrication of Nanostructured Electrodes

The great success of anodic alumina membranes is due to their morphological features coupled to both thermal and chemical stability. The electrochemical fabrication allows accurate control of the porous structure: in fact, the membrane morphological characteristics (pore length, pore diameter and cell density) can be controlled by adjusting the anodizing parameters (bath, temperature, voltage and time). This article deals with both the fabrication and use of anodic alumina membranes. In particular, we will show the specific role of the addition of aluminum ions to phosphoric acid-based anodizing solution in modifying the morphology of anodic alumina membranes. Anodic alumina membranes were obtained at −1◦ C in aqueous solutions of 0.4 M H3 PO4 added with different amounts of Al(OH)3 . For sake of completeness, the formation of PAA in pure 0.4 M H3 PO4 in otherwise identical conditions was also investigated. We found that the presence of Al(OH)3 in solution highly affects the morphology of the porous layer. In particular, at high Al(OH)3 concentration (close to saturation) more compact porous layers were formed with narrow pores separated by thick oxide. The increase in the electric charge from 20 to 160 C cm−2 also contributes to modifying the morphology of porous oxide. The obtained anodic alumina membranes were used as a template to fabricate a regular array of PdCo alloy nanowires that is a valid alternative to Pt for hydrogen evolution reaction. The PdCo alloy was obtained by electrodeposition and we found that the composition of the nanowires depends on the concentration of two metals in the deposition solution

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

A Multi-Criteria Decision-Making Framework for Zero Emission Vehicle Fleet Renewal Considering Lifecycle and Scenario Uncertainty

In the last decade, with the increased concerns about the global environment, attempts have been made to promote the replacement of fossil fuels with sustainable sources. For transport, which accounts for around a quarter of total greenhouse gas emissions, meeting climate neutrality goals will require replacing existing fleets with electric or hydrogen-propelled vehicles. However, the lack of adequate decision support approach makes the introduction of new propulsion technologies in the transportation sector a complex strategic decision problem where distorted non-optimal decisions may easily result in long-term negative effects on the performance of logistic operators. This research addresses the problem of transport fleet renewal by proposing a multi-criteria decision-making approach and takes into account the multiple propulsion technologies currently available and the objectives of the EU Green Deal, as well as the inherent scenario uncertainty. The proposed approach, based on the TOPSIS model, involves a novel decision framework referred to as a generalized life cycle evaluation of the environmental and cost objectives, which is necessary when comparing green and traditional propulsion systems in a long-term perspective to avoid distorted decisions. Since the objective of the study is to provide a practical methodology to support strategic decisions, the framework proposed has been validated against a practical case referred to the strategic fleet renewal decision process. The results obtained demonstrate how the decision maker's perception of the technological evolution of the propulsion technologies influences the decision process, thus leading to different optimal choices

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