bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrodeposition of Mo/Zn/Cu/Sn Unconventional Stack for CZTS Thin Films Synthesis
Authors: Panzeri Gabriele , Dell'Oro Ruben , Müller Dominic , Magagnin Luca 
Published: February 2020

The interest towards Cu2ZnSnS4 (CZTS) photoactive material relies into the abundancy and non-toxicity of the elements considered [1, 2]. Among the fabrication routes investigated in literature, the single layer approach, consisting in the electrodeposition of Cu, Sn, Zn layers followed by reactive annealing, is the most promising showing higher efficiency devices than coelectrodeposition-based ones. The typical stack order is Mo/Cu/Sn/Zn, where the electrodeposition of the most noble metal is followed by intermediate and subsequently by the least noble one [2, 3]. This layer sequence is strongly connected to water-based electrolytes where pH dependence limits the possible stack combinations. However, it was reported that the ideal layer stacking, fabricated by means of sputtering, would consider to have Zn as first layer to avoid its loss during the annealing treatments (high vapor pressure) and to promote a good interface with Mo [4]. In the present work, a traditional electrodeposition-annealing route of an unconventional stack order (Mo/Zn/Cu/Sn) is proposed by employing an organic solution based on ethylene glycol for the copper electrodeposition while an aqueous one for zinc and tin depositions. The electrochemical behaviour of the copper solution was investigated by means of cyclic voltammetry (CV) and linear sweep voltammetry. Galvanostatic approach was investigated, employing of Hull cell as preliminary test. Soft and reactive (sulfur atmosphere) annealing were performed; the formation of kesterite were verified by means of Raman spectroscopy. CZTS thin films were characterized by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD); photoelectrochemical characterization was performed to evaluate the photoactivity.

References

[1] Kumar, Mukesh, et al. "Strategic review of secondary phases, defects and defect-complexes in kesterite CZTS–Se solar cells." Energy & Environmental Science 8.11 (2015): 3134-3159.
[2] Colombara, Diego, et al. "Electrodeposition of kesterite thin films for photovoltaic applications: Quo vadis?." physica status solidi (a) 212.1 (2015): 88-102.
[3] Ahmed, Shafaat, et al. "A high efficiency electrodeposited Cu2ZnSnS4 solar cell." Advanced Energy Materials 2.2 (2012): 253-259.
[4] Araki, Hideaki, et al. "Preparation of Cu2ZnSnS4 thin films by sulfurization of stacked metallic layers." Thin Solid Films 517.4 (2008): 1457-1460.
A Mathematical Model and Experimental Examination of the Electrodeposition of Nanocatalysts on Various Substrates for Energy Conversion and Storage Applications
Authors: Karimi Shahram 
Published: February 2020

Pulsed electrodeposition of nanocatalysts from aqueous electrolyte solutions has received considerable attention on account of its ease of use, relative low cost, reproducibility, and access to several process parameters, compared with other widely used techniques. It is, therefore, desirable to determine the influence of different operating parameters to optimize the electrodeposition process. A detailed mathematical model, which includes the effects of ionic migration, was developed to accurately predict the influence of various electrodeposition parameters on the resulting electrodeposited layers in terms of size, distribution and catalytic activity. Most of the available models for pulsed electrodeposition are restricted to conventional square pulses and ignore contributions from the growth current during nucleation. The model presented here is based on progressive nucleation and takes into account contributions from both nucleation and growth currents. Furthermore, the model considers all contributing factors towards growth current, including diffusion, ohmic and charge transfer phenomena. Lastly, unlike many models that are restricted to a constant diffusion coefficient for a given species, the presented model is based on a system with varying diffusion coefficients for all active species in the electrolyte.
Nanocatalysts, including platinum, nickel, copper, and cobalt, were electrodeposited on different substrates employing a pulsed current electrodeposition (PCE) technique. Pulses with low duty cycle, high peak deposition current densities, and delivered in milli- and nano-second range utilizing square, triangular, and ramp-down waveforms were used. The presence of nanocatalysts, ranging from 2-50 nm in diameter, was confirmed by SEM and XRD. Additional electrochemical characterization techniques were also employed. According to the model, at high peak deposition current densities and low duty cycles, ramp-down waveform yields the highest nucleation rate, confirming the experimental findings in which nanoparticles generated with the above waveform produces the smallest average grain size, ranging from 2 to 10 nanometer in diameter for platinum nanocatalysts on carbon cloths and 5 to 50 nm in diameter for nickel and copper nanoparticles deposited on titania nanotubes.
Fabrication and Characteristics of Ni Doped Titania Nanotubes By Electrochemical Anodization
Authors: Tirano Joaquin , Zea Hugo , Bredol Michael 
Published: February 2020

The semiconductor properties of titanium dioxide (TiO2) offer an interesting alternative to convert sunlight into electrical energy by water splitting. This is because of its band gap, a high photogenerated charges mobility and the possibility to be doped both n-type and p-type. However, it has been found that charge recombination and low visible radiation sensitivity are the bottlenecks in the efficient solar energy conversion. Although in the last decade important advances in the synthesis of nanostructured morphologies with high interaction area like nanotubes have been achieved, the conversion efficiency growth has decreased. This is a logical result because there are intrinsic limitations imposed by the electronic properties of TiO2.
One of the alternatives to modifying the TiO2’s band gap and improving its photoactivity under visible light irradiation is to dope the nanotubes with transition metals. This option requires fabricating efficient nanostructured photoelectrodes with controlled morphology and specific properties able to offer a suitable surface area for metallic doping. Also, transition-metal oxides and hydroxides are frequently applied as low-cost water-splitting catalysts because they reduce the needed activation energy to overcome the kinetic barrier and increase the electrochemical reaction rate. There are thus important challenges and opportunities from the material science point of view that require a substantial effort for developing new knowledge and advancing in the controlled synthesis of this type of nanostructures. This research focuses on the synthesis and characterization of Ni doped titanium dioxide nanotubes (TNTs) for improving its photocatalytic activity in solar energy conversion applications. Initially, TNTs with controlled morphology were synthesized by two-step potentiostatic anodization of titanium foil. The anodization was carried out at room temperature in an electrolyte composed of ammonium fluoride, deionized water and ethylene glycol. Consequent thermal annealing of as-prepared TNTs was conducted in the air between 450 °C - 550 °C. Afterwards, the nanotubes were superficially modified by nickel deposition.
Studies of the morphology and crystalline phase of the samples, before and after nickel deposition, were carried out by SEM, EDS and XRD analysis. Determining the photoelectrochemical performance of photoelectrodes is based on typical electrochemical characterization techniques (OCP, EIS, LSV). Also, the morphological characterization associated electrochemical behavior analysis were discussed to establish the effect of nickel nanoparticles modification on the TNTs. The methodology proposed in this research allows using other transition metal for nanotube surface modification and studying new routes for improving the performance of low cost water-splitting catalysts.
Effect of Additives on the Process of Cobalt-Based Alloys Electrodeposition from Citrate Bath
Authors: Kwiecińska Anna , Plucik Monika , Kolczyk Karolina , Kutyla Dawid , Żabiński Piotr , Kowalik Remigiusz 
Published: February 2020

The electrochemical deposition of cobalt binary alloys with transition metals has received recently much attention due to some characteristic properties and possible practical applications of the coatings. These alloys, besides high electrocatalytical properties, exhibit useful properties such as high corrosion resistance and premium hardness. Additionally, these alloys are also seen as environmentally safe substitutes for hard chromium plating and a new materials for microelectronic and microelectromechanical systems and ultralarge-scale integrated systems.
The present work aims to deposit of active cobalt alloys as catalytic coatings for hydrogen evolution. Electrodeposition mechanism and kinetics of cobalt-based alloys deposition was studied by the electrochemical methods. Chronoamperometry and cyclic voltammetry techniques were combined with electrochemical quartz crystal microbalance to analyze this process in details. The proper adjustment of the process of electrolysis has a crucial role on the composition, and therefore structure and morphology of the deposited coatings, which decide about their electrocatalytic properties. In the present investigations, the composition of the citrate electrolyte with different additives, potential and current density were changed systematically in ranges within which they significantly effect on the composition and structure of the resulting cobalt alloys. The morphology, structure and the composition of the deposited alloys was identified by SEM, XRD, XRF and EDS techniques. Also we try to clarify the effect of the additives in enhancing the high activity for hydrogen evolution. The electroactivity of the coatings were analyzed by different electrochemical techniques.
This work was supported by the Polish National Center of Science under grants 2016/21/B/ST8/00431 and the research was carried out in the frames of COST Action MP1407 (e-MINDS).
Cobalt Electrodeposition at Different Substrates from a Deep Eutectic Solvent
Authors: Landa-Castro Midori , Gómez Valentín Elvira , Montes de Oca-Yemha María Guadalupe 
Published: February 2020

The global demand for materials that are possessing high yields in the energy conversion, storage and use, has led to new research. These materials with a high surface-volume ratio allow an increase in the contact area between the electrode and electrolyte. Nanometric materials, such as nanoparticles, nanowires, nanorods, and nanosheets, generally have a greater reversible capacity and long-term useful life. Developing alternative materials, where their structure, porosity and morphology are mainly adapted. The Co (II) evaluation process was carried out onto three different substrates: glassy carbon, Au/Ti/Si and platinum. The Co deposits were obtained from a Deep Eutectic Solvent (1ChCl: 2Urea), and characterized by Scanning Electron Microscopy (SEM). The SEM images show that the Co morphology at glassy carbon is similar to the desert roses (Figure 1), and a reticular structure for metallic substrates. X-Ray Diffraction (XRD) and X-Ray Photoelectron Spectroscopy (XPS) confirm that the deposits obtained correspond to the metallic cobalt. The potentiostatic experiments at low overpotentials show 3D nucleation and growth process on the glassy carbon substrate [1].
[1] L. Manh y M. Palomar Pardave, On Wetting Angles and Nucleation Energies during the Electrochemical Nucleation of Cobalt onto GC from a DES, Journal of The Electrochemical Society, 164, 12, pp. D694-D699, 2017.

Figure 1
Initial Zinc Electrodeposition on Copper Studied By in-Situ AFM
Authors: Neupane Shova , Oezaslan Mehtap , Renner Frank Uwe 
Published: February 2020

Zinc deposition on copper surfaces is being studied before, mostly as a model system to understand film formation but more recently also in the context of catalysis or Zn batteries [1]. Electrochemical deposition of zinc on copper enables to obtain different ratios of Cu and Zn in the deposit alloy layers [2]. Zn electrodeposition on Cu surfaces can be monitored by in-situ Atomic Force Microscopy (AFM) and allows to follow the initial growth of Zn on different copper surfaces [3,4]. In this work, we pretreated different textured polycrystalline Cu surfaces by chemical etching and electropolishing to modify and improve the surface quality. Surfaces are then pre-characterized by AFM, Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD). The local surface morphology is changed after the different surface pretreatments. In-situ AFM measurements of Zn electrodeposition were performed on as-received as well as pretreated Cu surfaces and monitored the initiation of Zn deposition in real time (Figure 1). Deposition of Zn on Cu surfaces critically depends on the Cu surface morphology and specific surface orientations. For applications, the surface morphology of the Zn deposition may play a critical role in controlling the performance of the films.
References:
[1] T. Otani et al Electrochem. Acta 242 (2017) 364-372
[2] F.Jia et al, J. Phys. Chem. 111 (2007) 8424-8431
[3] L. N. Poloni et al Chem.Matter . 29 (2017) 331−345
[4] S. Xu et al, J. Phys. Chem. 121 (2017) 3938−3946

Figure 1
3D Printing of Nanotwinned Metals
Authors: Minary Majid 
Published: February 2020

Microstructure of a metal determines its properties. A major effort in the field of additive manufacturing (AM) of metals is
controlling and predicting the microstructure. Nanotwinned (nt)-metals exhibit superior mechanical and electrical properties compared to their coarse-grained and nano-grained counterparts. nt-metals have a unique microstructure with grains that contain a high density of layered nanoscale twins divided by coherent twin boundaries (TBs). These metals often show higher strength and ductility compared to their nanocrystalline counterpart, since TBs can effectively block dislocation motion. These metals show more resistance to electromigration, which is a common problem for metals at the nano/ microscale. nt-metals in film and bulk forms are obtained using physical and chemical processes including pulsed electrodeposition (PED), plastic deformation, recrystallization, phase transformation, and sputter deposition. However, currently, there is no process for 3D printing (AM) of nt-metals. Given their unique properties, it is desirable to establish an AM process for nt-metals. We developed a new process for 3D printing of nt-metals, termed localized PED (L-PED). We demonstrate microscale 3D printing of nt-Cu with high density of coherent TBs using this process. This cost-effective process, which is performed at ambient environment, enables direct printing of 3D microscale structures of pure metals with nanoscale twins. The 3D printed nt-Cu is fully dense, with low to none impurities, and low microstructural defects, and without obvious interface between printed layers, which overall result in good mechanical and electrical properties, without any postprocessing steps.
Coupling Additive Manufacturing and Wet Metallization for Advanced Microfabrication
Authors: Bernasconi Roberto , Magagnin Luca 
Published: February 2020

Nano and microfabrication are general terms to indicate a broad selection of techniques suitable to produce functional structures at the nano or microscale. This ability is at the base of many advanced applications in the main fields of engineering. However, many techniques typically used in microfabrication, like lithography or thin film deposition, are characterized by a limited tridimensionality of the final product. These manufacturing methods are commonly said to operate in 2.5 dimensions, due to the limited envelope achievable in the vertical direction.
To overcome said limitations, 3D printing techniques able to work at the microscale have been introduced in the last few years. The application of such techniques, based on direct writing of the different layers that compose the object by mean of a laser beam, to microfabrication gave origin to a new concept of production: additive microfabrication [1]. The main disadvantage of methodologies like stereolithography (SLA) or two photons lithography (2PL) is the material used for printing: a mixture of photocurable polymers. The need to use resins implies significant limitations on the final properties of the object: relatively low mechanical properties and total or partial lack of conductivity. A possible approach to impart metallic properties to SLA or 2PL printed parts is the deposition of metal thin films on the surface of the 3D printed part.
In the present work, a possible hybrid production route that combines SLA and wet metallization is described in general and applied to real microfabrication. Electroless deposition on SLA resins has already been attempted in the past [2], as well as deposition of multilayers. Starting from these propaedeutic work, the hybrid SLA/wet metallization approach is here applied to the micromanufacturing of two prototypical devices belonging to two distinct classes: MEMS and magnetically steerable microdevices. These two selected applications demonstrate the applicability of the manufacturing methodology but does not limit the range of possible uses, which span from bioengineering to microelectronics or to microfluidics.
[1] Misawa, Hiroaki, ed. (2006). 3D Laser Microfabrication: Principles and Applications, Germany: Wiley
[2] R. Bernasconi, C. Credi, M. Tironi, M. Levi, L. Magagnin, Electroless Metallization of Stereolithographic Photocurable Resins for 3D Printing of Functional Microdevices. J. Electrochem. Soc. 164, B3059–B3066 (2017)
Operando XAS Studies: Electro-Reduction of CO2 on Nanoporous Cu Foams
Authors: Hecker Burkhard , Oezaslan Mehtap 
Published: February 2020

New and improved strategies to secure our global energy economy and chemical industry in the future are needed due to the strong dependence on limited fossil resources and the socio-environmental problems associated with increasing anthropogenic emissions of CO2. To counteract this problem and simultaneously to reduce the concentration of the CO2 as well-known greenhouse gas, a very promising route is the electrochemical CO2 reduction reaction (CO2RR) into hydrocarbons and alcohols. Different reaction mechanisms and kinetics for the CO2RR are postulated.[1-4] In particular, the role of Cu oxide during the C2 formation like ethylene and ethanol is poorly understood to date. Further critical issues are addressed: (i) high overpotentials, (ii) broad product distribution, (iii) fast degradation by catalyst poisoning and (iv) competition reaction at high cathodic potentials, referred to as hydrogen evolution reaction.
Our work is focusing on the fundamental understanding about the mechanism and kinetics for the CO2RR on nano-porous copper (np-Cu) foams probed by XAS technique. The np-Cu foams prepared by dealloying of Cu-based alloys or by electrodeposition exhibit large surface area-to-volume ratios, improved catalytic performance and high C2 selectivity compared to a flat Cu surface. The catalytic properties (activity and selectivity) can be controlled by the pore size and curvature of the ligaments of the np-Cu. By using operando X-ray absorption spectroscopy (XAS), we studied the various structures and oxidation states of the Cu species in np-Cu foams as function of the applied potential, kind of electrolyte and pH value during the CO2RR. Linear combination fitting and multi-edge EXAFS fit analysis provide us information about the potential-controlled changes of oxidation state and local environment of Cu. In addition, we identified the potential range for the catalyst aging via coarsening and suggest strategies to stabilize the ligament structure and size of the Cu foams during the CO2RR.
Based on our operando XAS studies, we obtained a deeper insight to the mechanism and kinetics of the CO2RR on porous Cu foams and clarified the role of Cu oxides for the C2 production.

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(Invited) Advanced Electrochemical Hydrogen Compressor
Authors: Hamdan Monjid 
Published: February 2020

U.S. automakers have invested significant resources in the research and development of hydrogen fuel cell vehicles (FCEVs). However, to enable the widespread use of FCEVs, an additional major investment will be required to achieve an infrastructure for hydrogen compression in fueling stations. In order to dispense hydrogen to FCEV tanks quickly the hydrogen must be compressed to a minimum of 875 bar at the fueling station.
Giner ELX has identified the use of mechanical hydrogen compressors as a key impediment to commercializing and implementation of high-pressure hydrogen refueling systems. Mechanical compressors have a high capital cost, high maintenance costs, poor reliability, and are noisy. The compressed hydrogen produced by a mechanical compressor often contains small amounts of pump oil; this oil will degrade performance of fuel cells receiving the hydrogen. Most importantly, the cost of a failure in a single hydrogen compressor oil filtering system will be very high, as considerable consequential damages will be incurred in on-board vehicle gas storage and fuel-cell systems. To eliminate the need for a mechanical compressor, and any chance of catastrophic oil contamination, Giner ELX has extended its extensive experience in high-pressure hydrogen-selective proton-exchange-membrane (PEM) to develop an electrochemical hydrogen compressor (EHC) system for refueling applications that can deliver hydrogen at pressures of greater than 875 bar.

The concept demonstrates a cost-effective method for compressing hydrogen while eliminating the need for mechanical compressors. In addition, Giner ELX has demonstrated high efficiency through the use of an EHC stack that operates at high current density and utilizes a hydrogen selective PEM and integral water management membrane. The program leverages current work being conducted by Giner ELX to improve EHC efficiency and reduce EHC costs while simultaneously raising the pressure in PEM-based stacks to greater than 350 bar.