Anodic oxidation of copper in alkaline solutions 2—the open-circuit potential behavior of electrochemically formed cupric hydroxide films

Copper electrodes covered with Cu(OH)₂ films grown in 1 mol dm⁻³ LiOH solution have been examined using X-ray diffractometry, scanning electron microscopy and electrochemical techniques. A sharp change in potential on open-circuit, due to a change in phase from Cu(OH)₂ to Cu₂O, was observed. This phase change is accompanied by a substantial amount of film dissolution. The time required for transformation, and the final amount of Cu₂O formed, are functions of both hydroxide ion concentration and electrode rotation speed. A mechanism involving Cu(OH)₂ dissolution, disproportionation (Cu²⁺+Cu→2Cu⁺) and Cu₂O precipitation, is proposed to explain these observations.     

Preparation and electrical properties of metal sulfides–amidoximated PAN composite film

To improve the electrical conductivity of polyacrylonitrile (PAN) film, metallic sulfides and PAN composite film were prepared by the chelating method. Dense PAN film and porous PAN film were prepared by dry process and wet process, respectively. These PAN films were treated to NH₂OH solution to introduce the amidoxime group coordinated with metallic ion. Cu⁺² and Cd⁺² ions were adsorbed to amidoximated PAN films, the sulfur ion was treated with metal-adsorbed PAN films, and thus CuS—and CdS–PAN composite films were prepared. The adsorptive capacity of amidoximated PAN film for the Cu⁺² ion was independent of the morphology of the PAN film, but the adsorptive capacity of the Cd⁺² ion on amidoximated PAN film was dependent on porosity of the polymer. Adsorptive capacity of amidoximated porous PAN film for Cd⁺² was improved about four times than that of amidoximated dense PAN film. The electrical conductivities of CuS–dense and porous PAN composite film were both 10^?1 S/cm in optimum condition, but because of the difference in adsorptive capacity, the electrical conductivities of CdS–dense and CdS–porous PAN composite films were 10^?9 S/cm and 10^?4 S/cm, respectively. Additionally, because CdS was known as a photoconductive material, the photoconductive properties of CdS–porous PAN composite film were investigated.     

Quantitative characterization of protective films grown on copper in the presence of different triazole derivative inhibitors

The protective films developed on copper by anodic polarization in a borate-buffered solution containing benzotriazole (BTAH), 1-hydroxybenzotriazole (BTAOH) or 3-amino 1, 2, 4-triazole (ATA) have been characterized using coulometric experiments and an electrochemical quartz crystal microbalance (EQCM). The combination of these two techniques has allowed the CuO and Cu₂O layers and the cuprous-organic layer to be analyzed quantitatively. In the presence of BTAOH, the oxide layers were very similar to those formed in inhibitor-free solution and BTAOH appeared to be adsorbed on the oxide film. In the presence of BTAH, a thick Cu₂O film was covered by a Cu-BTA film containing 8% Cu⁺ ions. Cupric oxide appeared on Cu₂O areas uncovered by Cu-BTA. In the presence of ATA, the Cu₂O layer was very thin and the greater part of Cu⁺ ions (75%) was involved in a thick Cu-ATA film.     

Influence of nucleation density on film quality,growth rate and morphology of thick CVD diamond films

The optimum growth parameters of our 5 kW microwave plasma CVD reactor were obtained using CH₄/H₂/O₂ plasma and high quality transparent films can be produced reproducibly. Among the films prepared in this system, the film of best quality has very smooth crystalline facets free of second nucleation and the full width at half maximum (FWHM) of the diamond Raman peak is 2.2 cm⁻¹, as narrow as that of IIa natural diamond. For this study, diamond films were grown on silicon substrates with low (10⁴–10⁵ cm⁻²) and high nucleation densities (>10¹⁰ cm⁻²), respectively. From the same growth run, a highly 〈110〉 textured 300 μm thick white diamond film with a growth rate of 2.4 μm/h was obtained from high nucleation densities (>10¹⁰ cm⁻²), and a white diamond film of 370 μm in thickness with a higher growth rate of 3 μm/h was obtained from low nucleation densities (5×10⁴–10⁵ cm⁻²) too. The effect of nucleation density on film quality, growth rate, texture and morphology was studied and the mechanism was discussed. Our results suggest that under suitable growth conditions, nucleation density has little effect on film quality and low nucleation density results in higher growth rate than high nucleation density due to less intense grain growth competition.     

Enhanced high rate properties of ordered porous Cu2O film as anode for lithium ion batteries

Highly ordered porous Cu₂O film is electrodeposited on copper foil through a self-assembled polystyrene sphere template. Compared with the dense Cu₂O film and the octahedral Cu₂O powder, the ordered porous Cu₂O film exhibits an improved electrochemical cycling stability. The capacity of the porous Cu₂O film can maintain 336 mAh g⁻¹ and 213 mAh g⁻¹ after 50 cycles at the rate of 0.1 C and 5 C, respectively. The reversible capacity holds 63.4% as the discharge-charge rate even increases by 50 times. The enhanced high rate properties of the ordered porous film should be attributed to the sufficient contact surface of Cu₂O/electrolyte and the short diffusion length of Li⁺. Moreover, the direct contact between Cu₂O and current collector and the decreasing inactive interfaces of Cu₂O/polymer binder are also suggested as being responsible for the enhanced high rate property.     

Untersuchung der teilströme der legierungs-auflösung und der deckschichtbildung an Cu70Zn30 in ammoniakalischer lösung mit der rotierenden scheiben-ring-elektrode

A quantitative electrochemical investigation of the formation of copper oxide films on Cu70Zn30 in [NH₃ + (NH₄)₂SO₄] solutions was carried out on the basis of measurements obtained using a rotating ring-disc electrode. It was found that the non-steady partial current densities of the alloy dissolution are prominent during the formation phase of the Cu₂O film and Cu₂/CuO transformation and that the film formation partial current densities in these ranges are considerably lower than during the quasi-stationary growth of both oxide films. Investigations into the influence of the rotation speed of the disc electrode on the disc current density have shown that a diffusion-controlled electrochemical process takes place during Cu₂O formation and that the Cu₂O/CuO transformation characterises the independence of the rotation speed of the electrode that is typical for film formation processes.     

Potentiostatic electrodeposition of cuprous oxide thin films for photovoltaic applications

Potentiostatic deposition of Cu₂O thin films on glass substrates coated with F-doped SnO₂ from an alkaline electrolyte solution (pH 12.5) containing copper (II) sulfate and lactic acid was studied for fabrication of a Cu₂O/Al-doped ZnO (AZO) heterojunction solar cell. The band gap of the electrodeposited Cu₂O films was determined by photoelectrochemical measurements to be around 1.9 eV irrespective of the applied potentials. The solar cells with a glass/FTO/Cu₂O/AZO structure were fabricated by sputtering an AZO film onto the Cu₂O film followed by deposition of an Al contact by vacuum evaporation. The highest efficiency of 0.603% was obtained with a Cu₂O film deposited at −0.6 V (vs. Ag/AgCl). This was attributed to better compactness and purity of the Cu₂O film than those of the Cu₂O films deposited at other potentials.     

Cyclic durable high-capacity Sn/Cu6Sn5 composite thin film anodes for lithium ion batteries prepared by electron-beam evaporation deposition

Sn/Cu₆Sn₅ alloy composite thin films were directly prepared by electron-beam deposition for anodes of lithium ion batteries. The thin film was comprised of micro/sub-microcrystalline Sn and Cu₆Sn₅, where the polyhedral micro-sized Sn grains were uniformly dispersed in the loose Cu₆Sn₅ matrix. Lithiation reaction kinetics were confirmed to be controlled by a diffusion step and the diffusion coefficient of Li⁺ in the thin film anode was determined to be 1.91 × 10⁻⁷ cm²/s. The galvanostatic cycling behavior of Sn/Cu₆Sn₅ composite thin film anodes was studied under different conditions. Stable capacities of more than 370 mAh/g were obtained by discharging from 1.25 to 0.1 V. Structure changes and fading mechanism of the thin film electrodes was discussed based on SEM, XRD and EDX investigations. The present results demonstrated that the multi-phase composite structure can improve electrochemical performance of the Cu-Sn alloy thin film electrodes.     

Insights into Cu2O thin film absorber via pulsed laser deposition

Cuprous oxide materials are of growing interest for optoelectronic devices and were produced by several chemical and physical methods. Here, we report on the structural, optical, and electrical properties of Cu_xO thin films prepared by the pulsed laser deposition technique. The substrate temperature, as well as the oxygen partial pressure in the deposition chamber, were varied to monitor the copper to oxygen ratio within the deposited films. The growth conditions were carefully optimized to provide the highest conductivity and mobility. Thus, 100 nm thick cuprous oxide films (Cu₂O) deposited at 750 °C exhibited a resistivity of 16 Ω?cm, high mobility of 30 cm²/(V?s), and a bandgap of around 2 eV. The film deposited at the optimized deposition parameters on Nb:STO (001) substrate with Au top electrode showed a photovoltaic response with an open circuit voltage of 0.56 V. These results path the way to efficient solar cells made with Cu₂O films via the pulsed laser deposition technique.     

Hydrothermal fabrication of p-Cu2O−n-ZnO films and their properties for photodegradation and ultraviolet sensors

This article reports spin coating and hydrothermal approaches to the synthesis of Cu₂O seed layer−ZnO and Cu₂O film−ZnO heterojunction films on fluorine-doped tin oxide substrates. Cu₂O seed layers and an ethylene glycol (EG) reducing agent were employed to obtain pure, uniform, and adhesive Cu₂O films on the substrate. Transmission electron microscopy validated the heterojunctions with clear interfaces between each component on the p-Cu₂O film−n-ZnO (with EG) sample, the conductive types of which were determined through Mott−Schottky measurements. Constructed energy band diagrams supported the Mott−Schottky result, manifesting favorable conduction band positions for the generation of •O₂⁻ radicals for all constituent materials and indicating smooth charge carrier transport for the p-Cu₂O film−n-ZnO (with EG) sample. Furthermore, abundant p−n junction interfaces synergistically enabled the sample to exhibit the most satisfactory photodegradation capability (rate constant ≈ 8.9 × 10⁻³ min⁻¹), which was attributable to the predominance of •OH radicals. The sample's rectifying (diode) behavior with a ratio of the current density (J) at +3 V (forward bias) to that at −3 V (reverse bias) of approximately 27 was observed without ultraviolet illumination. Moreover, the J at −3 V is under illumination approximately 80 times that without illumination, implying the suitability of the sample for UV detectability.     

The role of sulphur in the sulfurization of CZTS layer prepared by DC magnetron sputtering from a single quaternary ceramic target

The influence of sulphur vapour pressure, controlled by its mass, on the grain growth and optoelectronic properties of Cu₂ZnSnS₄ (CZTS) films prepared by a two-step procedure based on sputtering was studied. It was found that both the crystallinity and grain size of the films were promoted with the increase of the sulphur vapour pressure, indicating that the crystal growth was controlled by the sulphur vapour pressure. In addition, the crystal growth process of CZTS was investigated by analysing the microstructure and elemental composition of the sulfurized films with different masses of sulphur. It was also found that the content of Sn in the sulfurized films decreased after high-temperature annealing. However, the second phase SnS₂ was observed on the sample surface, which led to the increase of the optical band gap of the film. Moreover, we proposed the regulatory mechanism of sulphur vapour pressure in the grain growth of CZTS film. Finally, a highly crystalline p-type kieserite Cu₂ZnSnS₄ film with carrier concentration of 8.16?×?10¹⁷ cm^?3, mobility of 1.24?cm²/V?s and optical bandgap of 1.54?eV was obtained. This CZTS layers are expected to fabricate high efficiency thin film solar cells.     

Influence of Ca/Al Ratio on Properties of Amorphous/Nanocrystalline Cu–Al–Ca–O Thin Films

This article reports the characterization of thin films sputtered from CuAl_1?xCa_xO targets (x = 0, 0.05, 0.1, 0.15, and 0.2) at room temperature. All films exhibit amorphous/nanocrystalline structures. Their transparency increases slightly with the addition of Ca. Furthermore, the resistivity decreases as the Ca/Al atomic ratio increases. Transmission electron microscopy with energy dispersive spectroscopy mapping indicates that the composition is uniform throughout the films deposited from the highest Ca doping concentration target. Some nanocrystals are present at the top surface of the CuAl_0.8Ca_0.2O thin film as well as the interface region between the CuAl_0.8Ca_0.2O thin film and the glass substrate, whereas the interior of the film is pretty amorphous with some embedded nanocrystals. X‐ray photoelectron spectroscopy shows that the Cu²⁺/Cu⁺ atomic ratio increases with the Ca/Al atomic ratio, indicating the enhancement of p‐type conductivity from the nonisovalent Cu–O alloying.     

CuInSe2 films prepared by three step pulsed electrodeposition. Deposition mechanisms, optical and photoelectrochemical studies

p-Type semiconducting copper indium diselenide thin films have been prepared onto In₂O₃:Sn substrates by a recently developed pulse electrodeposition method that consists in repeated cycles of three potential application steps. The Cu–In–Se electrochemical system and the related single component electrolytes were studied by cyclic voltammetry to identify the electrode processes and study the deposition processes. In situ atomic force microscopy measurements during the first 100 deposition cycles denote a continuous nucleation and growth mechanism. Particles removed by film sonication from some of the films were characterized by transmission electron microscopy and determined to consist in nanoscopic and crystalline CuInSe₂. The remaining film is still crystalline CuInSe₂, as assessed by X-ray diffraction.The chemical characterization by combined X-ray photoelectron spectroscopy, X-ray fluorescence and inductively coupled plasma optical emission spectroscopy, showed that films were Cu-poor and Se-poor. Raman characterization of the as-grown films showed that film composition varies with film thickness; thinner films are Se-rich, while thicker ones have an increased Cu–Se content. Different optical absorption bands were identified by the analysis of the UV–NIR transmittance spectra that were related with the presence of CuInSe₂, ordered vacancy compounds, Se, Cu_2−xSe and In₂Se₃. The photoelectrochemical activity confirmed the p-type character and showed a better response for the films prepared with the pulse method.     

Morphologic and crystallographic studies on electrochemically formed chromium nitride films

Chromium nitride films were prepared by anodically oxidizing nitride ions at 0.4-1.5 V versus Li⁺/Li on chromium substrates in molten LiCl-KCl-Li₃N systems at 723 K. A crystalline Cr₂N film was successfully prepared at 0.4-1.4 V, and was thicker at more positive electrolytic potential. At 1.5 V, a Cr-N film could be also obtained, but its growth rate was relatively low. The film prepared at 1.5 V consisted of two distinctive layers. The surface layer was amorphous Cr-N containing crystalline CrN particles, and the inner layer was crystalline CrN. It was considered the existence of the amorphous phase suppressed the film growth.     

Long-term corrosion of copper in a dilute anaerobic sulfide solution

The mechanism of corrosion of oxygen-free copper has been studied in stagnant aqueous sulfide solutions using corrosion potential and electrochemical impedance spectroscopy (EIS) measurements. Film structure and composition were examined on surfaces and on cross-sections prepared by focused ion beam (FIB) milling using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Experiments were conducted in anaerobic 5 × 10⁻⁵ mol dm⁻³ Na₂S + 0.1 mol dm⁻³ NaCl solutions for exposure periods up to 4000 h (∼167 days) to mimic (at least partially) the conditions that could develop on a copper nuclear fuel waste container in a deep geologic repository. The corrosion film formed was a single cellular Cu₂S layer with a non-uniform thickness. The film thickness increased approximately linearly with immersion time, which implied that the sulfide film formed on the Cu surface is non-protective under these conditions up to this exposure time. The film growth process was controlled by HS⁻ diffusion partially in the aqueous solution in the pores in the cellular sulfide film and partially in the bulk of the aqueous solution.     

Electrochemical quartz crystal microbalance studies of thin-solid films of higher fullerenes: C76, C78 and C84

Thin-solid films of higher fullerenes, viz. C₇₆, C₇₈ and C₈₄, were prepared by the drop coating technique and characterized by simultaneous cyclic voltammetry and piezoelectric microgravimetry with the use of an electrochemical quartz crystal microbalance. Properties of the films were compared with those reported earlier for the C₆₀ and C₇₀ thin-solid films. The effect of nature of the counter cation on electrochemical properties of the films has been probed by employing acetonitrile solutions of two different 0.1 M supporting electrolytes, namely tetra(n-butyl)ammonium (TBA⁺) hexafluorophosphate and potassium hexafluorophosphate. Stability of the films with respect to dissolution depends on the fullerene oxidation state as well as on the nature of both the fullerene in the film and the counter cation in the supporting electrolyte. The TBA⁺ counter cation ingress to the film for compensation of the negative charge of the reduced fullerene is accompanied by the acetonitrile solvent intake. The number of acetonitrile molecules per TBA⁺ counter cation entering the film is higher the higher the fullerene. Also, the Langmuir films of higher fullerenes were prepared at the air-water interface and the film morphology was characterized by the Brewster angle microscopy.     

Modified sepiolite/PVDF-HFP composite film with enhanced piezoelectric and dielectric properties

Flexible film with both piezoelectric and dielectric properties is considered to be a potential candidate for the energy conversion and storage devices. In this study, the Li⁺ and H₂O modified sepiolite/poly(vinylidene fluoride-co-hexafluoropropylene) (LiSEP-H₂O/PVDF-HFP) composite films with both good piezoelectric and dielectric properties were prepared by traditional coating process. When the H₂O content was 13 wt %, the LiSEP-H₂O/PVDF-HFP composite exhibited high d₃₃ of 32 and dielectric constant of 48. Moreover, the effects of the Li⁺ and adsorbed H₂O on the d₃₃, F(β), dielectric constant, short-circuit currents were discussed. The adsorbed H₂O enhanced the β-phase by the hydrogen bonds and Li⁺ improved the polarization to realize the composite film with increased piezoelectric and dielectric properties respectively. We expected the common modification to lead other clay minerals realizing the future applications in the adjustment of composites' electric properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48412.     

The distribution of antimony in the oxide layer formed by potentiostatic oxidation of Pb-Sb alloy

The distribution of antimony within the oxide films on Pb-Sb alloy prepared by potentiostatic oxidation in H₂SO₄ solutions was examined by SIMS. The study of oxide films prepared by applying different potentials for three hours showed that two types of film were obtained depending on whether the potential was more negative or more positive than 1·5 V. Antimony profiles were obtained for films at several stages in the initial growth. It was found that antimony was retained in the oxide film at 1·5 V during both nucleation and two- or three-dimensional growth of PbO₂ and at 1·6 V during the lateral overlaps of three-dimensional centres of PbO₂. Relationships between the antimony distribution profiles and the oxide film growth are discussed.     

Changes of copper location in CuY zeolites induced by preparation methods

The location of transition ions in copper- and copper-zinc-loaded Y type zeolites prepared by different procedures has been studied by temperature-programmed reduction, infrared spectroscopy of CO adsorbed on pretreated samples and X-ray photoelectron spectroscopy. Samples outgassed at 673 K showed Cu⁺ species due likely to reduction of Cu²⁺ ions under vacuum. Over exchanged CuY zeolites copper species in exchange sites were detected, while an impregnated sample exhibited bands of CO adsorbed on both Cu²⁺ and Cu⁺ ions developed at the surface of CuO crystals, and small proportions of Cu⁺ ions located in accessible exchange sites S_II and Sn_II. Similar findings were observed in Zn- and Cu-exchanged zeolites although the relative proportion of Cu in S_I positions was decreased due to competition between Cu²⁺ and Zn²⁺ ions. Samples reduced in hydrogen at 523 K showed the appearance of Cu⁰ species in impregnated samples, whereas Cu⁺ dominated in the exchanged counterparts. Reduction at 598 K led to substantial changes in Cu-exchanged samples in water. The proportion of Cu⁺ species decreased by reduction to Cu⁰ and simultaneously migration to Cu⁺ to S_II sites occurred. While Cu²⁺ or Cu⁺ were found on outgassed samples, only Cu⁰ and intrazeolite Cu⁺ were observed after H₂-reduction at 623 K. Changes in copper exposure as a function of sample pretreatments were also revealed by X-ray photoelectron spectroscopy.     

The anodic dissolution of nickel—1: Perchlorate and fluoride electrolytes

A potentiostatic sweep technique has been used to study the anodic dissolution of nickel in acidic perchlorate, acetate and fluoride solutions. At slow potential sweep rates a prepassive film exists throughout the anodic region in perchlorate and acetate electrolytes. By the use of fast sweeps, or by the addition of F^?, film formation and growth is sufficiently reduced to reveal a linear anodic. Tafel region. The rate of active dissolution, which is independent of [H⁺] and [F^?], obeys the following rate law; i = 2Fka_w exp [βFE/RT], with β = 0·53.The following mechanism is proposed for active dissolution, with the first step rate-determining: (1) Ni + H₂O → NiOH_ads + H⁺ + e^?, (2) NiOH_ads → NiOH⁺ + e^?, (3) NiOH⁺ + H⁺ ? Ni²⁺ + H₂O. Prepassivation is thought to occur from the intermediate NiOH_ads through a solid state mechanism.