Copper Selenide Phases Research Articles

Phase Engineering of Nonstoichiometric Cu2-xSe as Anode for Aqueous Zn-Ion Batteries.

Aqueous zinc-ion batteries (AZIBs) are receiving widespread attention due to their abundant resources, low material cost, and high safety. However, the susceptibility of Zn metal anodes to corrosion and hydrogen evolution limits their further practical applications. Replacing Zn metal with intercalation-type anode material and constructing rocking-chair-type batteries could be an effective way to significantly prolong the cycle life of AZIBs. Herein, we present copper selenide with different crystal phase structures through a facile redox reaction as an anode for AZIBs. By comparing and analyzing different copper selenide phases, it is found that the cubic Cu2-xSe shows superior structural stability and highly reversible Zn2+ storage. Theoretical calculation results further demonstrate that the cubic Cu2-xSe possesses an increased electrical conductivity, higher Zn2+ adsorption energy, and reduced diffusion barrier, thereby promoting the storage reversibility and (de)intercalation kinetics of the Zn2+ ion. Thus, the Cu2-xSe anode delivers a long-term service life of over 15 000 cycles and impressive cumulative capacity. Furthermore, the full-cells assembled with the MnO2/CNT cathode operate stably for over 1500 cycles at 6 mA cm-2 at a negative/positive (N/P) capacity ratio of ∼1.53. This work provides a more ideal Zn-metal-free anode, which helps to push the practical applications of AZIBs.

Full Characterization of Sarcheshmeh and Khatoon-Abad Copper Anode Slimes: Characterization Impact on the Decopperization Operation

Copper anode slime, a valuable by-product generated during the electrorefining process, is an important secondary resource for the recovery of metals, such as gold, silver, selenium, tellurium, PGMs and copper. A full characterization of the anode slime is an essential part of the efficient recovery of these valuable metals. In this research, the refinery slimes of the Sarcheshmeh and Khatoon-Abad copper complexes, were fully characterized and compared using inductively coupled plasma (ICP), X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), differential thermal analysis (DTA), and particle size analysis. Besides the bottom cell slime characterization, properties of the Sarcheshmeh’s adherent slime was also analyzed and correlated. Sarcheshmeh copper slime particle size was found much smaller than the Khatoon-Abad slime. For both slimes though, the major part the gold and tellurium are located in larger than 38-micron particles. The main difference in thermal analysis of the two slime samples was originated from their selenium content difference. This has caused the higher concentration of non-selenide copper compounds at Khatoon-Abad slime, resulted in its easier copper recovery. Decopperization of both bottom-cell slimes were investigated and a significant difference in copper dissolution behaviors of the two slimes were observed due to their characteristic difference including the copper-selenide phases and capsulated copper in the barium sulfate agglomerates. Copper dissolution from Khatoon-Abad slime was observed to reach 90% comparing to 40% for Sarcheshmeh slime using atmospheric leaching.

Transformation of Nanostructures Cu2O to Cu3Se2 through Different Routes and the Effect on Photocatalytic Properties.

In this work, copper selenide (Cu3Se2 umangite phase) was synthesized by two routes, using a chemical reaction and the hydrothermal method to obtain CuSe-A and CuSe-H, respectively. The synthesis of Cu3Se2 consisted of a three-step process: in the first step, copper(I) oxide hexapods (Cu2O) were obtained as the copper reservoir; in the second step, selenium ions were obtained from the reduction of selenium powder; and in the third step involves mixing two precursors following the two synthesis routes mentioned before. Analysis of X-ray diffraction and X-ray photoelectron spectroscopy showed the formation of the Cu3Se2 phase by both synthesis routes. On the other hand, using the scanning electron microscopy (SEM) technique, it is observed that the Cu3Se2 sample (CuSe-A) is obtained by exchanging in solution with agitation and that the copper selenium phase grows only on the surface of the hexapods. Meanwhile, the hydrothermal route promotes a total conversion of copper(I) oxide hexapods to the copper selenide phase (CuSe-H). The resulting materials were tested as photocatalytic materials to remove methylene blue dye in water under sunlight irradiation. Cu3Se2 (CuSe-H) obtained by the hydrothermal route exhibited a higher efficiency of photodegradation of dye, reaching a removal percentage of 92% after 4 h under sunlight.

Electrochemical and Photoelectrochemical Characterization of Cu2SnSe3 Thin Films Deposited on Mo/Glass Substrates

Cu2SnSe3 (CTSe) thin films were fabricated by selenization of a Cu-Sn alloy, which was electrochemically co-deposited from a stirred citrate solution. Photoelectrical and optical properties of the obtained CTSe thin films were investigated by using only the electrochemical (we applied the cyclic voltammetry for determination the band gap of Cu2SnSe3 thin film semiconductor), photoelectrochemical and electrochemical impedance spectroscopy methods. New method is suggested, which allows to estimate the relationship between the etching time of secondary copper selenide phase and the photoelectrical properties (open circuit photopotential and photocurrent) of the CTSe thin films. The Cu2SnSe3 thin film with the best photo-response was obtained at a selenization temperature of 500°C. A significant improvement in photoelectrical behavior was observed on the CTSe thin film after 30 s of chemical etching in a 0.75 M KCN aqueous solution with the aim to remove the residual copper selenide phase. This film has a good photoelectrical and optical properties for solar cell formation: a p-type conductivity, a band gap of 0.92 eV, a carrier concentration Nα = 1.45 × 1017cm−3 and flat band potential EFB of 0.297 V vs. saturated hydrogen electrode and a photocurrent density of 0.44 mA × cm−2 at cathodic potential of −600 mV vs. saturated hydrogen electrode. A diagram of energy bands of the CTSe/electrolyte junction has been presented.

Copper Selenides as High-Efficiency Electrocatalysts for Oxygen Evolution Reaction

Designing high-efficiency water oxidation catalysts from earth-abundant resources has attracted significant attention in the last couple of years owing to the potential application of this technology in several energy conversion devices. Among the transition metals, copper is one of the cheapest earth-abundant nonprecious element which can enhance electrocatalytic activity due to heavily occupied d-orbitals. In this article we have shown electrocatalytic activity of copper selenide for the first time for water oxidation reaction. The copper selenide phases were synthesized by direct electrodeposition on electrodes, as well as by hydrothermal and chemical vapor deposition (CVD) techniques. Structure and morphology characterization through powder X-ray diffraction, Raman, X-photoelectron spectroscopy, and electron microscopy revealed that all the synthesized phases were pure crystalline copper selenide of composition Cu2Se and comprising nanostructured granular morphology. Electrocatalytic performance for w...

Properties of ZnO-Cu_2-xSe thin films deposited by sputtering from composite ZnSe-Cu_2O targets

Amorphous and polycrystalline ZnO-Cu2-xSe composite thin films were deposited by rf sputtering using a single target prepared from mixtures of ZnSe and Cu2O powders. Films were grown from three different targets with Cu2O atomic concentrations of 12, 36 and 60% for substrate temperatures between room temperature and 400 °C. The transmittance, reflectance and electrical properties were dependent upon the Cu2O concentration in the target and on the substrate temperature. The optical properties of the polycrystalline films were determined by the copper selenide phases present in the films, which allows foreseeing applications as coatings for windowpanes with strong infrared rejection. The electrical characterization showed that the ZnO-Cu2-xSe composite films are n-type with resistivity values in the range from 3x10−3 to 3x103 Ω⋅cm.

Control over the preferred orientation of CIGS films deposited by magnetron sputtering using a wetting layer

A growth method is presented to control the preferred orientation in chalcopyrite CuIn x Ga1-x Se2 (CIGS) thin films grown by magnetron sputtering. Films with (220/204) and (112) preferred orientation as well as randomly oriented films were prepared. The effects of an In2Se3 wetting layer and the working pressure on the texture transition phenomena were examined. A large-grained CIGS film with (220/204) texture was formed at 400°C with the inclusion of a thin (80 nm) In2Se3 layer and liquid phase (excess copper selenide phase) formation, and the reaction mechanism is proposed. The device deposited at 2.0 Pa on an In2Se3 layer exhibited the optimal electrical properties.

Co-operativity in a nanocrystalline solid-state transition

Co-operativity is a remarkable phenomenon mostly seen in biology, where initial reaction events significantly alter the propensity of subsequent reaction events, giving rise to a nonlinear tightly regulated synergistic response. Here we have found unique evidence of atomic level co-operativity in an inorganic material. A thousand-atom nanocrystal (NC) of the inorganic solid cadmium selenide exhibits strong positive co-operativity in its reaction with copper ions. A NC doped with a few copper impurities becomes highly prone to be doped even further, driving an abrupt transition of the entire NC to the copper selenide phase, as manifested by a strongly sigmoidal response in optical spectroscopy and electron diffraction measurements. The examples presented here suggest that cooperative phenomena may have an important role in the solid state, especially in the nucleation of new chemical phases, crystal growth, and other materials' transformations.

Synthesis and characterization of copper gallium diselenide powders prepared from the sol–gel derived precursors

Abstract Copper gallium diselenide (CuGaSe 2 ) powders were synthesized via the sol–gel method followed by a selenization process. The sol–gel process can effectively reduce the required synthesis temperature to 400 °C due to enhanced reactivity and improved composition homogeneity. The amount of Cu 2 Se impurity phase was decreased when sufficient Ga 3+ was added to the precursors. CuGaSe 2 powders were successfully prepared when the Ga 3+ /Cu 2+ molar ratio was increased to 2. The formation of CuGaSe 2 with a pure chalcopyrite structure was confirmed via the Rietveld refinement analysis. With decreasing Ga 3+ /Cu 2+ molar ratios, the particle size of the prepared CuGaSe 2 powders was significantly enlarged because the copper selenide phase acted as a flux for the particle growth. The optical absorption spectra revealed the obtained CuGaSe 2 to have a band gap of 1.68 eV. The sol–gel method combined with the selenization process was demonstrated to provide a potential approach for fabricating CuGaSe 2 materials.

Zn incorporation and (CuIn) 1− xZn 2 xSe 2 thin film formation during the selenization of evaporated Cu and In precursors on Al:ZnO coated glass substrates

CuInSe 2 thin films with typical 1.0 eV gap energy and tetragonal chalcopyrite structure have been obtained on soda–lime glass substrates by the reaction of sequentially evaporated Cu and In layers with elemental selenium vapor, at 500 °C in flowing Ar. When analogous deposition and reaction processes were performed on Al:ZnO coated glasses, some increment in the band gap energy and diminution in the crystalline interplanar spacings have been detected for the resulting films with an extent that depends on the Cu/In atomic ratio of the evaporated precursor layers. This fact has been related to Zn incorporation into the selenized film, with quaternary (CuIn) 1− x Zn 2 x Se 2 compound formation that is influenced by the presence of copper selenide phases during the reaction process. Such deductions are supported by the optical, structural and compositional characterizations that have been performed comparatively on samples prepared by selenization of evaporated metallic precursors with two different Cu/In ratios (0.9 and 1.1) on bare and Al:ZnO coated glass substrates.

Growth and characterization of CuInSe 2 thin films via one-step electrodeposition from a lactic acid/sodium lactate buffer system

In this work, we describe the development of a novel bath comprising lactic acid/sodium lactate pH buffer for electrodeposition of CuInSe 2 (CIS) thin films, by which long-term bath stability was found to be improved and near-stoichiometric CIS films with smooth surface morphology were obtained. XRD and SEM studies reveal a dramatic improvement of the crystalline quality of CIS films after selenization treatments. Raman study confirms the absence of copper selenide phases in the CIS films. Optical study shows that the band gap energy of the obtained CIS film is 0.98 eV. The resultant photovoltaic device shows a conversion efficiency of 1.55%.

Sol–gel silica thin films with copper selenide

The silica sol–gel films with copper selenide produced by the selenization of metallic copper nanoparticles were fabricated. The composition of the films was studied with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and optical absorption spectroscopy. Several copper selenide phases were detected with XRD and contribute into the complicated behavior of core levels (Cu2p, Se3d, and Si2p) and Auger levels (Cu) in the XPS analysis. The optical absorption features of the films in the visible and near-infra red range are presented. The consistent interpretation of experimental data is proposed based on assumption of copper multivalence in the system “particles–silica matrix”.

Effect of a Cu–Se secondary phase on the epitaxial growth of CuInSe 2 on (1 0 0) GaAs

The effect of a secondary copper selenide phase that appears during epitaxial growth of CuInSe 2 (CIS) films on (1 0 0) GaAs substrates was investigated. CIS films with different copper to indium molar ratios were deposited on (1 0 0) GaAs substrates at 360 °C by migration-enhanced epitaxy. Films grown under In-rich conditions were polycrystalline, whereas films grown with a Cu-rich composition were epitaxial, as evidenced by pole figure analysis, even when the copper composition was only slightly higher than the 1:1 Cu:In molar ratio. The epitaxial film growth followed a Stranski–Krastanov mode and contained both matrix and island regions. Grazing incidence XRD revealed a small amount of CIS with the Cu–Au-like structure near the surface of the island regions. A binary Cu–Se secondary phase aggregated near the surface in the island regions of the film, as determined by electron probe microanalysis (EPMA) before and after etching in 10% KCN. It is proposed that a Cu–Se phase present during the growth of Cu-rich CIS films enhances the mobility of adatoms on the substrate surface, allowing the film to grow epitaxially to a critical thickness. After that critical thickness is attained, the Cu–Se phase segregates at dislocation sites to nucleate the island regions. TEM-EDX scans of cross-sections also suggested a small amount of the Cu–Se secondary phase segregates on the film surface.

Effect Of Grain Size, Morphology and Deposition Temperature on Cu(InGa)Se2 Solar Cells

ABSTRACTCu(InGa)Se2 films have been deposited by multisource elemental evaporation at substrate temperatures from 550 to 400°C to determine the effect of temperature on grain size and morphology and on solar cell performance. Films were deposited with different flux profiles to compare cases where a copper selenide phase is formed during different stages of growth or not at all. The grain size and surface area of the films are determined by analysis of atomic force microscope images. With the Cu-rich growth, the mean lateral grain area decreases from 1.8 to 0.3 μm2 as substrate temperature decreases. Device efficiency decreases with the lower temperature but cannot be simply attributed to changes in grain size, surface area, or the availability of sodium which diffused from the glass substrate. Instead the decrease in open circuit voltage and fill factor are attributed to a greater density of intra-grain trap states in the Cu(InGa)Se2.

Effect of oxygen on the CuCu 2SeAg system

A large percentage of the world's silver supply is produced as a byproduct of the copper industry. The silver is found in the copper anodes which are upgraded by electrorefining. The anode composition and the phase distribution in the anode affect the electrorefining step and subsequently the separation processes for the various elements which are present in the anode. In particular, the distribution of silver and the other precious metals between the copper-rich phase and the copper selenide rich phase in the anodes has an effect on their recovery. In the present research the effect of oxygen on the CuSeAg (Pt, Pd, Au, or Ni) system was studied. Samples of copper-rich liquid and copper selenide-rich liquid were equilibrated at temperatures in the range of 1130°C to 1223°C. The silver content of both the phases reached a constant value after about two hours. Also, the oxygen content of the copper-rich phase reached an essentially constant value. However, the oxygen content of the copper selenide rich phase continuously increased due to the production of oxide phases in the melt. The oxygen content of both phases increased with the partial pressure of oxygen. At high oxygen potentials the silver distribution ratio between the copper and the copper selenide phases decreased because of the oxidation of some of the copper selenide to copper oxide. Silver as either oxide or metal has a much higher solubility in copper oxide than copper selenide and thus the silver distribution ratio decreased. Nickel additions resulted in a significant increase in the oxygen content of both phases.

Improvement of the optical properties of electrodeposited CuInSe 2 thin films by thermal and chemical treatments

Cu, In and Se have been codeposited in thin films by potentiostatic one-step electrodeposition. The as-deposited material has shown direct optical transitions attributable to the CuInSe 2 semiconductor, but also additional absorption corresponding to another semimetallic phase. The secondary phases are selenium and copper selenide compounds which have been determined by composition measurements. In order to eliminate the semimetallic phases and to improve the semiconductor behaviour of the electrodeposited material, thermal and chemical treatments have been performed. After heat-treatment of the samples at 400°C in flowing argon, elemental selenium loss has been detected together with an enhancement of the allowed direct optical transition. The subsequent chemical etching of the layers in a KCN solution has showed to be successful in eliminating the copper selenide phases which were responsible of the remaining sub-bandgap absorption.

Quarternary equilibrium phase diagram for copper, indium, selenium and oxygen

An equilibrium quaternary phase diagram is derived to study the effect of oxygen incorporation in thin films of CuInSe 2 grown by various techniques, with particular emphasis on chemical spray pyrolysis. This quaternary diagram is, to our knowledge, the first reported to date. Oxygen is found to be unstable with CuInSe 2 and its incorporation produces In 2O 3. An increase in oxygen incorporation, an increase in pH or a decrease in copper-to-indium ratio in the original spray solution results in the formation of copper selenide phases instead of In 2O 3. Over a relatively narrow range of the latter parameters, single-phase CuInSe 2 should grow according to the phase diagram. Experimental results are provided to substantiate these findings.