Electrodeposition In Aqueous Solution Research Articles

Spontaneous Seed Formation during Electrodeposition Drives Epitaxial Growth of Metastable Bismuth Selenide Microcrystals.

Materials with metastable phases can exhibit vastly different properties from their thermodynamically favored counterparts. Methods to synthesize metastable phases without the need for high-temperature or high-pressure conditions would facilitate their widespread use. We report on the electrochemical growth of microcrystals of bismuth selenide, Bi2Se3, in the metastable orthorhombic phase at room temperature in aqueous solution. Rather than direct epitaxy with the growth substrate, the spontaneous formation of a seed layer containing nanocrystals of cubic BiSe enforces the metastable phase. We first used single-crystal silicon substrates with a range of resistivities and different orientations to identify the conditions needed to produce the metastable phase. When the applied potential during electrochemical growth is positive of the reduction potential of Bi3+, an initial, Bi-rich seed layer forms. Electron microscopy imaging and diffraction reveal that the seed layer consists of nanocrystals of cubic BiSe embedded within an amorphous matrix of Bi and Se. Using density functional theory calculations, we show that epitaxial matching between cubic BiSe and orthorhombic Bi2Se3 can help stabilize the metastable orthorhombic phase over the thermodynamically stable rhombohedral phase. The spontaneous formation of the seed layer enables us to grow orthorhombic Bi2Se3 on a variety of substrates including single-crystal silicon with different orientations, polycrystalline fluorine-doped tin oxide, and polycrystalline gold. The ability to stabilize the metastable phase through room-temperature electrodeposition in aqueous solution without requiring a single-crystal substrate broadens the range of applications for this semiconductor in optoelectronic and electrochemical devices.

(Invited) In-Situ Observation of Electrodeposition Processes By High Speed Scanning Probe Microscope

Electrodeposition is important technology for developing the novel functional materials such as MEMS. In nanotechnology term, the metal deposition is one of the hot topics since it can control the surface structure precisely and easily. Generally, in metal electrodeposition, an adatom deposited on the electrode diffuses and reaches a step or kink before forming a crystal. In the process, the solvents and additives adsorbed on the surface are often incorporated into the deposits. Since they works as an impurity in the film, they induce the crystal defects and surface defects, which may cause the performance degradation of the produces. Because each processes occur at high speeds and on the atomic scale, the deposition mechanism is difficult to understand. The methods for observing the nucleation have been developed in various ways. With the invention of the scanning probe microscope (SPM) in the 1980’s, we could directly observe the nanostructure. It has been applied to the electrodeposition in aqueous solution. However, since SPM usually takes some time to observe the surface, it is very difficult to catch the dynamic process such as the nucleation and growth of the deposits. Therefore, I believe that the high-speed SPM is the promising solution of both temporal and special problems. There are two types of SPM: scanning tunneling microscope (STM) and atomic force microscope (AFM). In the former type, there is a video rate STM (Video STM) that can capture up to 30 frames per second. Furthermore, the spatial resolution can reach the atomic scale. For example, the Bi kink growth along the step is reported and Pb surface diffusion on the Cu surface is clarified [1-3]. However, since the tunneling current flows continuously between the probe and the substrate during the measurement, it is necessary to sufficiently consider the effects on electrochemical reactions. Although the resolution of the high-speed scanning AFM (HS-AFM) is inferior to that of the STM, the influence of the probe can be less. Therefore, in addition to the nucleation phenomenon during Cu electrodeposition (Fig. 1-A) [4], we have observed the weak adsorption of PEG polymer that is known as the major additives during the electrodeposition (Fig.1-B). By taking the advantage of the low contact pressure of the probe, the transient behavior of nucleation and growth of electrolytic nanobubbles can be observed. In this presentation, the dynamic variations of the electrolytic nucleation & growth by using a high-speed SPM will be presented. References H. Matsushima et al., Faraday Discuss., 193 (2016) 171.A. Taranovskyy et al., Phys. Chem. Chem. Phys., 14 (2012) 10579.S. Guezo et al., J. Phys. Chem. C, 115 (2011) 19336.T. Yoshioka et al., Electrochim. Acta, 302 (2019) 422. Figure 1

Controllable synthesis of NiCo-LDH/Co(OH)2@PPY composite via electrodeposition at high deposition voltages for high-performance supercapacitors

Global energy crisis require facile preparation of electronic devices with high energy and power densities. Eletrodeposition is a simple way to fabricate electrode materials. Applying a voltage beyond the water decomposition potential during electrodeposition in aqueous solutions is counterintuitive. Herein, we first applied −2.0 V during electrochemical deposition process to obtain a hierarchical electrode structure. Specifically, NiCo layered double hydroxide with Co(OH)2 (NiCo-LDH/Co(OH)2) and polypyrrole (PPY) composite (NiCo-LDH/Co(OH)2@PPY) were synthesized on Ni foam via electrodeposition at room temperature. By subtle control of deposition voltage and time, the as-prepared materials exhibit a cauliflower-like nanostructure, which is beneficial for electrolyte infiltration and charge transfer. PPY coating can also improve the electric conductivity of the electrode. As a result, the NiCo-LDH/Co(OH)2@PPY electrode shows an outstanding specific capacitance of 2132 F g−1 at a current density of 11 A g−1. Additionally, an asymmetric supercapacitor (ASC) with NiCo-LDH/Co(OH)2@PPY as cathode and active carbon as anode demonstrates high energy density and long cycling stability, implying great application potential of high-voltage electrodeposition.

The Full-Cell Design of a Li-Ion Capacitor Using a Sn-Ni Alloy As an Anode

Lithium-ion capacitors (LIC) is composed of a capacitors-type cathode and battery-type anode. Thus, LIC has been considered as a favorable electrochemical energy storage device to bridge the lithium-ion batteries (LIB) and supercapacitors.1 We have reported that the synthesis of Sn-Ni alloy by electrodeposition in aqueous solution and its electrochemical behaviors as an anode for LIB and LIC.2,3 Through the above reports, we confirmed that the LIC consisting of Sn-Ni anode shows higher energy and power density than graphite anode based LIC because of high theoretical capacity of Sn (997 mAh g-1). Herein, the material characterization of Sn-Ni alloy was carried out. Besides, full-cell performances of LIC were tested and compared depending on with/without cell optimization.The Sn-Ni alloy is synthesized by electrodeposition using aqueous electrolyte consisting of Tin(II) chloride dihydrate and Nickel(II) chloride. The material characteristics of Sn-Ni alloy were examined by field emission scanning electron microscopy, X-ray diffraction, glow discharge optical emission spectroscopy, and inductively coupled plasma analysis. The electrochemical performances of Sn-Ni anode and LIC full-cell were tested using alf- and full-cell.The Sn-Ni alloy synthesized by electrodeposition has Ni3Sn4 phase which affects the reversible reaction of Sn-Ni alloy as an anode during lithiation/de-lithiation.2 For that reason, Sn-Ni alloy shows a good discharge performance as an anode for LIC (Fig. 1(a)). The in-depth chemical properties of Sn-Ni alloy was examined by GDOES (Fig. 1(b)). The region from the surface to around 6.9 μm shows that the Sn and Ni are mixed. After that, Cu peak corresponding to the Cu substrate was increased, resulting in an intermediate layer consisting of Sn, Ni, and Cu. The Cu signal after 29.4 μm is relatively higher than Sn and Ni, implying that only Cu substrate was presented. This result indicates that the Sn and Ni are mixed from top of Sn-Ni alloy to middle of film with a thickness of approximately 29. 4 μm.Full-cell optimization of LIC was conducted by mass balancing between cathode and anode. It was confirmed that LIC with cell optimization shows improved energy density and power density compared to LIC without cell optimization. Also, LIC consisting of Sn-Ni anode have higher energy and power density than LIC assembled using graphite anode (Fig.1 (c)). Through the above discussion, we believe that this report provides a blueprint for high-performance LIC with Sn-Ni alloy anode.(Figure 1)Fig. 1 (a) XRD patterns, (b) GDOES curves of Sn-Ni alloy, and (c) Ragone plot of LIC. Acknowledgement This work is partially supported by Advanced Low Carbon Technology Research and Development Program of the Japan Science and Technology Agency (JST-ALCA, JPMJAL1008).

Model improvement for super-Nernstian pH sensors: the effect of surface hydration

The maximum sensitivity of pH sensors is given by the Nernst equation, and its theoretical value is 59.2 mV pH−1. However, countless sensors developed and reported in the literature have their sensitivity higher than the Nernstian limit. These are called super-Nernstian sensors. To understand the causes of this behavior, the sensitivity of polyaniline thin films was studied by evaluation of an important parameter: the hydration of the film’s surface. Sensitivities were measured before and after varied heat treatments, and the sensor's parameters were associated with the amount of water lost in the process. Polyaniline thin films were fabricated by galvanostatic electrodeposition in aqueous solution, and their sensitivity was measured before and after heating of the samples. An endothermic process, typical of evaporation, was revealed by the analysis of mass loss during the heating process. A decrease in the sensitivity of the films was observed after heating process. For comparison, polyaniline thin films were also fabricated by spin coating, in the absence of water, and their sensitivity proved to be smaller than for the galvanostatically fabricated ones and it did not change significantly after the heating processes. The results indicated that the Nernst model can be adjusted using a parameter ( $$1/r$$ ) related to the hydration of the surface of the sample, which directly affects the sensitivity of the thin films. The lowest reachable $$1/r$$ value for samples containing no water is approximately 0.9. The parameter also describes the upper limits for the sensitivity of super-Nernstian sensors.

Morphology control and optical characterization of three-dimensional ordered macroporous Cu films from template-assisted electrodeposition

Three-dimensional ordered macroporous (3DOM) Cu films with the size 300–500 nm were prepared on FTO by colloidal crystal template-assisted electrodeposition in aqueous solution. The effects of electrodeposition methods and electrodeposition parameters on the morphology and structure of the 3DOM copper films were studied. It is found that the constant potential method is more suitable for the preparation of 3DOM copper films compared to the step electrodeposition method, the deposition voltage affects the grain size and the flatness of the copper film surface and the electrodeposition time affects the dimension and the number of layers of the copper films. The optical properties of the prepared 3DOM copper films were also analyzed.

The Influence of Pyridinium-Based Additives on Zinc Electrodeposition in Aqueous Solution

The suitability of N-ethylpyridinium bromide as a potential electrolyte additive for zinc electrodeposition in aqueous solution has been investigated by a combination of cyclic voltammetry, bulk electrolysis, scanning electron microscopy, synthesis and NMR spectroscopy. The current magnitudes of the Zn/Zn(II) redox reaction observed at the electrode decreased dramatically after a single deposition/stripping cycle in the presence of N-ethylpyridinium bromide at switching potentials more negative than −1.30 V vs Ag/AgCl. This is attributed to the reduction of the N-ethylpyridinium cation to form a pyridyl radical that subsequently and rapidly dimerizes. The proposed dimer was synthesized and shown to have a low solubility in aqueous solutions, consistent with a passivation of the electrode surface by precipitation and inhibition of redox behavior. Based on this understanding for the pyridinium cation reduction, alternative pyridinium-based additives have been examined in order to determine their influence on zinc electrodeposition.

Oriented Transformation from Layered Zinc Hydroxides to Nanoporous ZnO: A Comparative Study of Different Anion Types.

Thermal decomposition of layered zinc hydroxides (LZHs) is a simple and convenient way to achieve porous ZnO nanostructures. The type of anion contained in an LZH determines the fundamental characteristics of the LZH and thus affects the formation process of the resulting porous ZnO. Here we report a comparative study on the crystal orientation relationship between LZH precursors and the corresponding porous ZnO products by using well-faceted and highly oriented LZH crystals with three different anions, i.e., NO3-, SO42-, and Cl-. Highly oriented LZH crystals were prepared on layer-by-layer coated indium tin oxide substrates by electrodeposition in aqueous solution and were transformed into porous ZnO by calcination in air. The synthesized materials were characterized by X-ray diffraction, scanning electron microscopy with electron backscatter diffraction, Fourier transformed infrared spectroscopy, and X-ray photoelectron spectroscopy. The layered structure of the highly oriented LZHs was parallel to the substrate surface and all transformed to nanoporous ZnO with a ⟨0001⟩ preferred orientation. The ⟨0001⟩ orientation degree and in-plane orientation of the nanoporous ZnO differed significantly depending on the type of anion but not the decomposition temperature, revealing that the initial formation process of ZnO from the LZHs is crucial. Finally, a possible transformation mechanism explaining the difference in the resulting ZnO orientation by anions (NO3-, SO42-, and Cl-) is discussed on the basis of their layered structure and thermal decomposition processes.

Optimization of Anion Exchange Membranes Derived from Cross-linked Chitosan-Poly (diallyldimethylammonium chloride) for All-solid Electrochemical Capacitors

Carbon dioxide can be formed in many ways, especially in combustion, it is one of the most important reasons lead to greenhouse effect and global warming. So many scientists devoted themselves to techniques that can reduce CO2 emissions. Among these promising techniques, electrochemical ways provide a efficient means, as it can convert carbon dioxide into fuels and other useful materials.[1,2] This way has many advantages: (a) the process is controllable by setting the temperature of electrode; (b) the system can take advantage of new energy resources and the production do not contaminate environment; (c) the system is compact and easily operated; (d) the experiment can be operated under normal atmospheric pressure and temperature.[3,4] In this paper, Tin-Cu alloy was deposited on carbon paper by electrodeposition in aqueous solution, which was employed as a cathode for electrochemical reduction of CO2 to formate, and how to obtain big catalytic current density, high efficiency and high production rate of formate were explored and discussed. Tin-Cu alloys with different compositions were characterized by morphology, structure, and composition. The electrochemical behavior of the alloys was measured by EIS and CV analysis. In addition, FE, partial current density (PCD), and concentration of HCOO− on the alloys were investigated and compared with those on Sn and Cu electrodes.

On the electrochemical synthesis and characterization of p-Cu2O/n-ZnO heterojunction

A p-Cu2O/n-ZnO heterojunction was grown directly on fluorine-doped tin oxide (FTO) substrate by two-step electrodeposition in aqueous solution. The electrical characteristics of the p-Cu2O/FTO and n-ZnO/FTO were studied using the Mott-Schottky (M-S) analysis in the electrolyte solution. High donor and acceptor concentrations were obtained for ZnO and Cu2O layers, respectively. The p-Cu2O/n-ZnO heterojunction show long electron lifetime and high electron–hole separation efficiency according to the electrochemical impedance spectroscopy (EIS) measurements and photocurrent response. The morphological, structural, optical, and electrical characteristics of p-Cu2O/n-ZnO heterojunction were investigated by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), UV–Vis and photoluminescence (PL) analysis. The FE-SEM cross-section images confirm the formation of well-defined cubic Cu2O grains on continuous and flat surface of ZnO layer. XRD result points to high crystallinity of (111)-oriented p-Cu2O layer on (101)-oriented n-ZnO layer. The optical band gap energies of n-ZnO and p-Cu2O thin film are 3.3 and 2.3 eV, respectively. The current–voltage (I–V) characteristics of Au/p-Cu2O/n-ZnO/FTO heterojunction shows well-defined rectifying behavior with turn on voltage of 0.5 V in dark and high photoresponse under illumination.

Effect of Oxide Intermediate Layers on Pyramidally Textured Cu2O/ZnO Solar Cells Prepared By Electrodeposition

Thin-film oxide solar cells composed of a pn heterojunction of p-type cuprous oxide (Cu2O) and n-type zinc oxide (ZnO) have attracted increasing attention as a promising candidate for a low-cost and environment-friendly photovoltaic device because the main constituent elements of copper, zinc, and oxygen are earth abundant and non toxic. In this solar cells, p-type Cu2O with a bandgap energy of 2.1 eV acts as a solar light absorber, and exhibits a theoretical conversion efficiency of ca. 18%. To date, many efforts have been devoted to develop the fabrication methods and improve the photovoltaic conversion efficiency of Cu2O/ZnO-based solar cells.1 We have reported that p-Cu2O/n-ZnO heterojunction can be formed using only electrodeposition in aqueous solutions (< 80°C), where no vacuum process and no post annealing were employed.2 This preparation method, therefore, potentially offers a simple and large scalable route to more low-cost and environment-friendly solar cells. To improve the conversion efficiency, we recently prepared pyramidally textured ZnO films by electrodeposition.3 Pyramidally textures are a well-known structure that exhibits a large light-scattering effect, making efficient solar-light absorption possible. Indeed, the obtained pyramidally textured ZnO films showed a high haze value of 52% in the visible region, and pyramidally textured Cu2O/ZnO solar cells showed a 1.3 times higher short circuit current density than that using a traditional planar ZnO.3 As another approach to improve the conversion efficiency, we demonstrated that electrodeposited highly resistive ZnO thin layers inserted between the Cu2O/ZnO interface can act as an effective intermediate layer.4 Oxide intermediate layers with a wide bandgap energy, such as gallium oxide (GaO x ) and zinc-magnesium oxide (ZnMgO x ), have also been reported to act as an effective interface buffer layer.1 In the present study, these oxide intermediate layers have been inserted between the pyramidally textured Cu2O/ZnO interface to further improve the conversion efficiency. The oxide intermediate layers were prepared using solution processes including electrodeposition and spin-coating techniques, and the photovoltaic performances were evaluated. In one case, for example, a ~1.7 times higher conversion efficiency was achieved by using a solution-processed GaO x intermediate layer, where both the short circuit current density and open circuit voltage increased significantly. Acknowledgement: This work was supported by JSPS KAKENHI, JAPAN.

Cu2O photoelectrodes for solar water splitting: Tuning photoelectrochemical performance by controlled faceting

Cuprous oxide (Cu2O) films were grown by electrodeposition in aqueous solutions of varying pH. The effect of bath pH on morphology, structural, and photoelectrochemical (PEC) properties of Cu2O films was investigated. XRD showed that all prepared films were polycrystalline Cu2O, without formation of competing phases such as CuO and Cu. The film grown in the solution with a pH of 8 is made up of Cu2O crystallites with preferential (200) planes exposed. The films deposited at solution pH values of 10, 12 and 14 exhibit Cu2O crystallites with preferential (111) planes exposed. As photoelectrodes these Cu2O films generate photocurrent upon light illumination. The Cu2O film grown in the solution with pH of 12 shows the best PEC performance for hydrogen generation. The (111) facets of the Cu2O film were stable without corrosion during the PEC test. A mechanism for the preferred faceting in alkaline solution has been discussed.

Multiphysics coupling simulation of RDE for PCB manufacturing

Purpose– The purpose of this paper is to optimize experimental parameters and gain further insights into the plating process in the fabrication of high-density interconnections of printed circuit boards (PCBs) by the rotating disc electrode (RDE) model. Via metallization by copper electrodeposition for interconnection of PCBs has become increasingly important. In this metallization technique, copper is directly filled into the vias using special additives. To investigate electrochemical reaction mechanisms of electrodeposition in aqueous solutions, using experiments on an RDE is common practice.Design/methodology/approach– An electrochemical model is presented to describe the kinetics of copper electrodeposition on an RDE, which builds a bridge between the theoretical and experimental study for non-uniform copper electrodeposition in PCB manufacturing. Comsol Multiphysics, a multiphysics simulation platform, is invited to modeling flow field and potential distribution based on a two-dimensional (2D) axisymmetric physical modeling. The flow pattern in the electrolyte is determined by the 2D Navier–Stokes equations. Primary, secondary and tertiary current distributions are performed by the finite element method of multiphysics coupling.Findings– The ion concentration gradient near the cathode and the thickness of the diffusion layer under different rotating velocities are achieved by the finite element method of multiphysics coupling. The calculated concentration and boundary layer thicknesses agree well with those from the theoretical Levich equation. The effect of fluid flow on the current distribution over the electrode surface is also investigated in this model. The results reveal the impact of flow parameters on the current density distribution and thickness of plating layer, which are most concerned in the production of PCBs.Originality/value– By RDE electrochemical model, we build a bridge between the theoretical and experimental study for control of uniformity of plating layer by concentration boundary layer in PCB manufacturing. By means of a multiphysics coupling platform, we can accurately analyze and forecast the characteristic of the entire electrochemical system. These results reveal theoretical connections of current density distribution and plating thickness, with controlled parameters in the plating process to further help us comprehensively understand the mechanism of copper electrodeposition.

硝酸铵诱导电沉积氧化锌纳米柱的铝掺杂及光学性质操控

To allow the ZnO nanorod arrays in new thin film solar cells to capture photons and to collect carriers effectively,a method to improve the conductivity of the ZnO nanorods and to control their optical properties was researched. Al-doped ZnO nanorod arrays were prepared by electrodeposition in aqueous solutions with Zn(NO3)2,NH4NO3 and Al(NO3)3.The experimental results indicate that the properties of ZnO nanorods such as the diameter,density and distance could be adjusted by controlling the NH4NO3 concentration in the electrolyte.The use of NH4NO3 in the solution leads to an increase of the Al/Zn weight ratio in the ZnO nanorods.By controlling the NH4NO3 concentration in the solution,the optical band gap of ZnO nanorod can be adjusted between3.72—3.76 eV,and the optical properties of the nanorod such as the transmission,reflection and absorption can be controlled.The Stokes shift of the Al-doped ZnO nanorods was in the range of377—449 meV,indicating the nonradiative recombination in the nanorods.Therefore the use ofNH4NO3 in the electrolytes has successed in enhancing the Al doping in the ZnO nanorods and controlling their optical properties.

Lawson Cypress Leaf-Like ZnO Hierarchical Nanostructures by Self-Assembly

In this letter, Lawson cypress leaf-like ZnO hierarchical nanostructures with new and interesting morphology were synthesized by electrodeposition in aqueous solution of Zn (NO3)2followed by annealing process, this structure was the first time appearing in ZnO nanostructure. The obtained Lawson cypress leaf-like ZnO hierarchical nanostructures were composed of ZnO nanoparticles with the grain size about 100~200 nm, were observed by scanning electron microscope (SEM), ZnO was detected by X-ray diffraction (XRD), and the highly crystalline structure was demonstrated by high-resolution transmission electron microscopy (HRTEM). Lawson cypress leaf-like ZnO hierarchical nanostructures, which are well-controlled in diameter, space and thickness, have potential applications in photoelectronic devices, sensors, solar cells and nanometer devices.

Electrodeposited ZnO-nanowire/Cu₂O photovoltaic device with highly resistive ZnO intermediate layer.

Cl-doped ZnO-nanowire (Cl:ZnO-nws)/Cu2O photovoltaic devices were prepared by electrodeposition in aqueous solutions, and the effects of the insertion of the highly resistive ZnO (i-ZnO) layer has been demonstrated by an improvement of the photovoltaic performance. The Cl:ZnO-nws and i-ZnO layer were prepared by electrodeposition in a zinc chloride aqueous solution with saturated molecular oxygen and simple zinc nitrate aqueous solution, respectively. The i-ZnO layer was directly deposited on the Cl:ZnO-nws and suppressed the electrodeposition of the Cu2O layer on the Cl:ZnO-nws. The insertion of the i-ZnO layer between the Cl:ZnO-nws and Cu2O layers induced an improvement in the photovoltaic performance from 0.40 to 1.26% with a 0.35 V open circuit voltage, 7.1 mA·cm(-2) short circuit current density, and 0.52 fill factor due to the reduction of the recombination loss.

Preparation of Cu 2ZnSnS 4 films by electrodeposition using ionic liquids

We report a new technique for the growth of Cu 2ZnSnS 4 (CZTS) thin films. The CZTS thin films were successfully formed by electrodeposition in ionic liquid and sulfurized in elemental sulfur vapor ambient at 450 °C for 1.5 h using Argon as the carrier gas. Experimental data on X-ray diffraction indicated that the film has a kesterite structure with preferred grain orientation along (1 1 2). It is found that the energy bandgap of the film is about 1.49 eV and the optical absorption coefficient is in the order of 10 4 cm −1. The results are compared to a control film grown by e-beam deposition of elemental stacked layers followed by the same sulfurization process. The data show that the two films have comparable optoelectronic properties indicating that electrodeposition in ionic liquid is a viable process for the growth of CZTS films for applications in photovoltaic device. The XRD results also indicate an absence of the oxide peak in the material, which is commonly found in films grown by electrodeposition in aqueous solutions.

Pulse-plating electrodeposition and annealing treatment of CuInSe 2 films

CuInSe 2 (CIS) thin film was prepared on molybdenum substrate using pulse-plating electrodeposition in aqueous solution. The most suitable pulse potential range for co-deposition is found to be from −0.55 to −0.75 V (vs SCE) from linear potential scanning curve. The electrodeposited films were characterized by X-ray diffractometry (XRD), scanning electron microscopy(SEM) and energy dispersive X-ray analysis (EDS). The annealing effects on electrodeposited precursors were investigated. And the influence of pulse parameters on film quality was studied. The chalcopyrite phase CuInSe 2 films with smooth surface and stoichiometric composition are obtained at a pulse potential from −0.65 to −0.7 V (vs SCE), a pulse period of 1–9 ms with a duty cycle of 33% and annealing treatment.

Influence of annealing temperature on the opto-electronic characteristics of znte electrodeposited semiconductors

Thin film ZnTe semiconductors for photovoltaic applications were prepared by electrodeposition in aqueous solution at −0.75 V (SCE). X-ray diffraction analysis showed that polycrystalline ZnTe films were produced by annealing the deposits at 375 and 400 °C. A filamentshaped morphology was observed in the electrodeposited samples, with a larger surface homogeneity for the films annealed at higher temperature. A direct energy gap of 2.3 eV at 400 °C was found, in agreement with the literature. Sheet resistance, free carrier concentration and Hall mobility values were also determined. A decrease of majority carrier concentration and an increase of carrier mobility with the annealing temperature was related to the decrease of the level of crystallographic defects in the sample treated at 400 °C.

Electrodeposition as a means of producing large-surface electrodes required in water electrolysis

Electrodeposition in aqueous solution is commonly used to produce the catalytic electrodes required in water electrolysis. By conducting deposition under appropriate conditions, an electrode may be obtained which has a considerably increased surface area compared with its apparent surface, and the electrocatalytic performance of the electrode can be greatly improved. In this work, we reviewed the major techniques at present employed in electrodeposition for fabricating large-surface electrodes used in water electrolysis, which include high current density deposition, composite electrodeposition, reactive deposition and electrodeposition-activation processes. We studied the functions of the techniques, their limitations and related problems. We also noticed inadvertent changes in electrode surface area resulting from electrodeposition under different conditions, and that only electrochemically accessible surface areas of the electrodes are useful in water electrolysis.