Copper Sulfide Films Research Articles

The kinetics of film growth and their influence on the susceptibility to pitting of copper in aqueous sulphide solutions

ABSTRACTThe formation of copper sulphide films on copper in aqueous sulphide solutions has been investigated under both natural corrosion and electrochemical conditions. Film growth occurs at the Cu2S/electrolyte interface and involves Cu+ transport through a generally porous film. Both corrosion and anodic film growth are suppressed by high chloride concentrations. Passivity, a pre-requisite for pitting, is achievable only at high sulphide concentrations and transport fluxes, conditions not expected under most geologic repository conditions since both sulphide groundwater concentrations and diffusive transport rates are expected to be low.This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems.

Gaining Hands-On Experience with Solid-State Photovoltaics through Constructing a Novel n-Si/CuS Solar Cell

A solid-state p–n junction photovoltaic cell can be fabricated in a common chemistry lab. It is prepared by coating a p-type copper sulfide film on an n-type silicon wafer via a simple chemical bath deposition method. The resulting p–n junction shows an obvious photovoltaic effect. This activity offers students an opportunity to gain hands-on experience with the technology of solid-state solar cells.

Properties of thin films of tungsten sulfide and copper sulfide produced by magnetron sputtering method

This article describes investigations into the properties of thin films of tungsten sulfide and copper sulfide produced by magnetron sputtering on glass substrates in argon atmosphere. Transmittance spectra of the obtained films are studied by spectrophotometry in the range from 300 to 900 nm; the band gaps are determined. The thickness of the obtained films varies in the range of 0.5–1 μm.

Nanostructured copper(I) sulfide films: Synthesis, composition, morphology, and structure

Possibility of forming the solid phase of copper(I) and (II) sulfides in ammonia and acetate solutions at pH values exceeding 10 was demonstrated by calculation with the use of thiocarbamide. Mirror-like nanocrystalline layers of exclusively monovalent copper sulfide Cu2S of stoichiometric composition with thicknesses of up to 110 ± 10 nm were formed on glass-ceramic substrates at 298–343 K via chemical deposition from solutions of both kinds due to the reducing properties of thiocarbamide. The films produced from the acetate system are more uniform and are constituted by globules (~10 nm) forming agglomerates up to 80–150 nm in diameter. According to X-ray diffraction data, they are crystallized in the chalcocite structure (space group P21/c) with crystal lattice constants a = 1.5307(5) A, b = 1.1908(5) A, c = 1.3485(6) A, and β = 116.60(1)°.

Fabrication and mechanical durability of a superhydrophobic copper surface with morphological development from hydrothermal reaction

The superhydrophobic surface on copper is fabricated by using a simple hydrothermal reaction and subsequent perfluorosilane treatment. The micro-structured and nano-structured surface was directly obtained through the hydrothermal reaction of copper sheets with sulfur at 180 °C for 12 h, resulting in the formation of copper sulfide film on the copper substrate. The chemical composition of this film was confirmed using X-ray photoelectron spectroscopy. After copper sulfide film is treated by perfluorosilane, the superhydrophobic surface with static water contact angle of 153 °C and a low contact angle hysteresis is achieved. The superhydrophobic surface shows strong mechanical stability and can effectively protect the copper substrate. Copyright © 2016 John Wiley & Sons, Ltd.

Enhanced electrocatalytic activity of electrodeposited F-doped SnO2/Cu2S electrodes for quantum dot-sensitized solar cells

Copper sulfide (Cu2S) films were deposited on F-doped SnO2 (FTO) substrates via the electrodeposition (ED) of copper (Cu) nanoparticles followed by sulfurization. The Cu nanoparticles were deposited on FTO substrates for various ED times ranging from 10 to 30 min at a constant −0.4 V. The FTO/Cu films consisted of flower-like nanoparticles comprised of randomly-clustering nanoflakes. The Cu nanoparticles electrodeposited for 10 min (FTO/Cu (10 min)) were dispersed sparsely over the FTO substrate, whereas the FTO/Cu (20 and 30 min) provided increased coverage. Unlike FTO/Cu2S (10 min), the FTO/Cu2S (20 and 30 min) consisted of vertically-standing large Cu2S nanosheets with numerous small nanosheets in between. This was attributed to the sufficient number of Cu seed nanoflakes, which not only facilitate ion transport of the redox couple but also increased the surface area, leading to significantly enhanced electrocatalytic activity. The quantum dot-sensitized solar cell (QD-SSC) with FTO/Cu2S (20 min) exhibited a significantly improved cell efficiency of 4.58%, compared to those with Pt and FTO/Cu2S (10 min). The QD-SSC with the FTO/Cu2S (30 min) showed similar cell efficiency to that with the FTO/Cu2S (20 min), despite the larger surface area because of its amorphous crystallographic structure offsetting the electrocatalytic activity.

(Invited) Assembling Nanoscale Building Blocks through Electrophoretic Deposition for Batteries, Supercapacitors, Catalysis, and Printable Electronics

Our research group works to gain a fundamental understanding of how to program and process nanoscale building blocks into functional structures, and the structure-property relationships of the resulting nanostructured materials. We seek to develop new nano-materials and methods for batteries, supercapacitors, fuel cells, and printable electronics. For building blocks we mainly utilize monodisperse nanoparticles made through colloidal chemistry. One issue that has yet to be adequately addressed for colloidal nanoparticles is their adherence to each other and to the electrically conductive support. In this talk I will discuss our recent results overcoming critical challenges to create functional assemblies from nanoparticles using electrophoretic deposition (EPD). For batteries, we have found that EPD can be used to form additive-free battery electrodes from colloidal nanoparticles. Typically, polymeric binders are necessary to adhere the particles to each other and the substrate, and carbon additives are necessary to increase conduction. These additives, however, generate a weight increase of 10−40%. We have found that EPD creates a strong electrical and mechanical bond for nanoparticles adhesion, enabling the batteries to perform at maximum capacity. This innovation increases the power density by reducing the overall volume. We have demonstrated high-performing anodes of cobalt oxide, Ge, and metal sulfides. The Co3O4films show high gravimetric (>830 mAh/g) and volumetric capacities (>2100 mAh/cm3) even after 50 cycles. The additive-free Ge nanoparticle films show stable capacities past 50 cycles at 750 mAh/g. Using EPD methods we have made additive-free nanoparticle electrodes for supercapacitors. We synthesized a series of Co-Mn-O stoichiometries to understand how cationic substitution affects performance. We find that the highest-performing Co−Mn mixture has a 1:1 ratio of Co to Mn and shows an energy density of 26.6 Wh/kg with a specific capacitance of 173.6 F/g. This nanoparticle electrode delivers the highest power density of 3.8 kW/Kg at a 5 A/g constant current discharge. The energy density and power density delivered by the optimal mixture is ~6× and ~3× higher, respectively, than that of pure Co3O4 electrodes. The specific capacitance for the Co-Mn mixture is also ~4× better than the pure Co3O4supercapacitor. For electrocatalysis, we compare EPD-deposited nanoparticle films to the conventional dropcast method. We study cobalt oxide thin films for the oxygen reduction/oxygen evolution reactions (ORR and OER). In examining the film’s catalytic properties we find that the electrophoretically deposited nanoparticles outperform the dropcast films by as much as 2.5 for the oxygen reduction reaction and 2.6 and the oxygen evolution reaction when accounting for both surface area and mass. This process results in this significant catalytic improvement in oxygen reduction/evolution performance which cannot be duplicated by dropcast films with the same loading. We have applied these techniques to make printable electronics: Using our surface treatment methods to link the nanoparticles, and the EPD method for deposition, we make copper sulfide films with high conductivity and high mobilities. We show that our nanoparticle films have conductivities that are on par with many bulk copper sulfide films (~75 S·cm-1), without the need for heat-treatments. D.-H. Ha*, T. Ly*, J.M. Caron, H. Zhang and R.D. Robinson, “A General Method for High-Performance, Additive-Free Li-ion Battery Electrodes from Colloidal Nanoparticles: The Case of MnS, Cu2-xS, and Ge,” ACS Appl. Mater. Inter. 7, 25053-25060 (2015) DOI: 10.1021/acsami.5b03398 D.H. Ha, M.A. Islam, and R.D. Robinson, “Binder-free and Carbon-free Nanoparticle Batteries: A Method for Nanoparticle Electrodes without Polymeric Binders or Carbon Black,” Nano Letters 12, 5122-5130 (2012). http://dx.doi.org/10.1021/nl3019559 S.D. Perera, X. Ding, A. Bhargava, R. Hovden, A. Nelson, L.F. Kourkoutis, R.D. Robinson, “Enhanced supercapacitor performance for equal Co-Mn stoichiometry in colloidal Co3-xMnxO4 nanoparticles, in additive-free electrodes,” accepted Chem. Mater. (2015) 10.1021/acs.chemmater.5b02106 M. Fayette, A. Nelson, and R.D. Robinson, “Electrophoretic Deposition Improves Catalytic Performance of Co3O4 Nanoparticles for Oxygen Reduction/Oxygen Evolution Reactions,” Journal of Materials Chemistry A 3, 4274–4283 (2015). DOI: 10.1039/C4TA04189EO.O. Otelaja, D.-H. Ha, T. Ly, H. Zhang, and R.D. Robinson, “Highly Conductive Cu2-xS Nanoparticle Films through Room Temperature Processing, and an Order of Magnitude Enhancement of Conductivity via Electrophoretic Deposition,” ACS Applied Materials and Interfaces 6, 18911–18920 (2014). http://dx.doi.org/10.1021/am504785f

Spectrally selective CuS solar absorber coatings on stainless steel and aluminum

CuS and ZrO2/CuS thin films have been deposited at 200 °C in ambient atmosphere by spray pyrolysis onto stainless steel S304 and aluminum AA1050 sheets in order to be used as prospective solar absorbers for thermal energy harvesting. Zirconia has been deposited as a top layer working as an antireflection coating increasing the solar absorption and protecting the underlying copper sulfide layer, which works as the solar light absorbing material. Solar selectivity of the samples was evaluated measuring the total hemispherical reflectivity in the ultraviolet‐visible infrared range and calculating solar absorptance and thermal emittance. The solar selectivity was optimized by tuning the film thickness of the coating stack. X‐ray diffraction, SEM and X‐ray photoelectron spectroscopy analyses have been used to proof crystal phase, coverage, film thickness, and surface contamination of optimized samples, revealing that the copper sulfide film is CuS covellite and the optimized film thicknesses are in the range of 50 nm for the ZrO2 top layer and 140 nm for the CuS layer. Copyright © 2016 John Wiley & Sons, Ltd.

Atomic layer deposition of copper sulfide thin films

Atomic Layer Deposition (ALD) of copper sulfide (CuxS) thin films from Cu(acac)2 (acac=acetylacetonate=2,4-pentanedionate) and H2S as Cu and S precursors is reported. Typical self-saturated reactions (“ALD window”) are obtained in the temperature range Tdep=130–200°C for an average growth per cycle (GR)=0.25Å/cycle. The morphology, crystallographic structure, chemical composition, electrical properties and optical band gap of thin films were investigated using scanning electronic microscopy (SEM), X-ray diffraction under Grazing Incidence conditions (GI-XRD), X-ray reflectivity (XRR), energy dispersive spectrometry (EDS), Hall effect measurements, and UV–vis spectroscopy. The obtained copper sulfide films are heavily p-doped (charge carrier concentration~1021–1022cm−3) with optical band gaps in the range of 2.2–2.5eV for direct and 1.6–1.8eV for indirect band gaps. Depending on the number of ALD cycles, multiphase compounds (made of digenite Cu1.8S, chalcocite Cu2S, djurleite Cu31S16 and covellite CuS) or single-phase digenite Cu1.8S films are obtained via a growth mechanism that involves in-situ copper reduction and loss of sulfur by evaporation.

Synthesis, Morphological and Optical Properties of Nano-Crystalline Solid CuxS Thin Films

Metal chalcogenide thin films of copper sulfide (CuxS) were grown on glass substrate using the chemical bath deposition. The CuxS thin film XRD studies reveal chalcocite low and covellite phases called as copper-rich and copper-poor form. The average grain size was calculated in the range of 8.87–69.65 nm. The optical band gap was estimated using Tauc's plot and found to be 3.02–4.06 eV. Optical properties exhibit that film find application in photovoltaic and photo thermal fields. AFM studies show formation of spherical shaped nanoparticle together with fine particles ranging 10 to 500 nm, evenly distributed showing homogeneity in polycrystalline thin film formation. SEM studies reveal spherical grain formation with cracks and pin holes at some places.

Structural, chemical and optical properties of the polyethylene–copper sulfide composite thin films synthesized using polythionic acid as sulfur source

Synthesis and properties of thin copper sulfide films deposited on polyethylene were explored for the development of low cost hybrid organic–inorganic photovoltaic materials. Polyethylene was used as a model organic host material for thin copper sulfide film formation. Adsorption–diffusion method was used which utilized consecutive exposure of polyethylene to polythionic acid followed by aqueous Cu(II/I) solution. Several crystalline copper sulfide phases were obtained in synthesized samples and elucidated using X-ray diffraction. Surface chemical composition determined using X-ray photoelectron spectroscopy showed the presence of copper sulfides in combination with copper hydroxide. Thickness of the composite material films ranged from several microns to ∼18μm and depended on the Cu(II/I) exposure time. Bandgap of the materials obtained was measured and ranged from 1.88 to 1.17eV. Importantly, heating these complex copper sulfide crystalline phase containing films at 100°C in inert atmosphere invariably resulted in a single copper sulfide, anilite (Cu1.75S), phase. Anilite possesses a bandgap of 1.36eV and has demonstrated excellent photovoltaic properties. Thus, the method described in this work can be used for a low cost large scale composite thin film photovoltaic material deposition based on anilite as photoactive material.

Fabrication of superhydrophobic copper sulfide film for corrosion protection of copper

A copper sulfide (digenite phase, Cu9S5) film composed of hierarchical microprotrusions was fabricated for corrosion protection of the underlying Cu substrate. The copper sulfide microprotrusions follow a heterogeneous nucleation, growth and aggregation mechanism. After hydrophobization with stearic acid, the film exhibits a water contact angle of 163° and a sliding angle of ~2°, and shows enhanced corrosion resistance. The mechanism of corrosion protection is clarified according to the proposed equivalent circuits, which show that the superhydrophobic film behaves as an effective barrier and largely separates the Cu substrate from the corrosive solution. The film exhibits good chemical stability against acidic or basic solutions due to the chemical inertness of copper sulfide. It shows good adhesion to the substrate and maintains its hydrophobic property after abrasion test.

A novel high-performance electrode: in-situ growth of copper sulfide film on copper foil for the application of supercapacitor

Copper sulfide (CuS) microspheres were directly grown on a copper foil via the redox reaction between CuSO4 and Na2S2O3. The morphology of the CuS film was observed by SEM and TEM, while the crystalline and structure were revealed by XRD pattern and UV spectrum. The electrochemical properties of the CuS electrodes were investigated by the cyclic voltammetry, galvanostatic charge–discharge and cycle stability technologies in 1 mol L−1 KCl electrolyte. The dependence of the concentration of CuSO4 and Na2S2O3 and reaction time on the properties of CuS films was discussed in detail. By means of these above comparisons, the CuS electrode that was obtained in 0.1 mol L−1 reactants concentration and 18 h reaction time possessed the homogeneous morphology, excellent electrochemical properties and good energy storage capacity. The specific capacitance was as high as 1443 F g−1 at a discharge density of 1 A g−1 and remained 1098 F g−1 after 2500 circles in the cycle life test.

New insight into copper sulfide electrocatalysts for quantum dot-sensitized solar cells: composition-dependent electrocatalytic activity and stability.

Despite recent significant strides in understanding various processes in quantum dot-sensitized solar cells (QDSSCs), little is known about the intrinsic electrocatalytic properties of copper sulfides that are the most commonly employed electrocatalysts for the counter electrode of QDSSCs. Given that the physical properties of copper sulfides are governed by their stoichiometry, the electrocatalytic activity of copper sulfides toward polysulfide reduction may also be dictated by their compositions. Using a new, simple approach to prepare robust copper sulfide films based on chemical bath deposition (CBD), we were able to delicately control the compositions of copper sulfides, which allowed us to perform a systematic investigation to gain new insight into copper sulfide-based electrocatalysts. The electrocatalytic activity is indeed dependent on the compositions of copper sulfides: Cu-deficient films (CuS and Cu1.12S) are superior to Cu-rich films (Cu1.75S and Cu1.8S) in their electrocatalytic activity. In addition, the stability of the Cu-deficient electrocatalysts is substantially better than that of the Cu-rich counterparts.

The influence of sulphide transport on the growth and properties of copper sulphide films on copper

The kinetics of Cu2S (chalcocite) film growth on corroding copper surfaces were monitored by following the change in pH in anaerobic aqueous sulphide solutions. Under stagnant conditions film growth was controlled by SH− diffusion in solution, and the formation of a non-protective film allowed complete consumption of available SH−. When accelerated by convection, film growth rapidly became controlled by Cu+ transport through a coherent protective film and proceeded at a considerably slower rate.

Key parameters determining structure and properties of sulphide films formed on copper corroding in anoxic sulphide solutions

The corrosion behaviour of copper was studied in anoxic solutions containing different concentrations of sulphide (10−5–10−3 mol L−1) and chloride (0·1–5 mol L−1) under stagnant and controlled convective conditions. The main determinants of the structure and properties of the copper sulphide (Cu2S) films formed are the rate of sulphide transport to the surface relative to the rate of its interfacial reaction with copper, and competition between sulphide and chloride for surface adsorption sites. When sulphide diffusion is rate limiting, the sulphide film formed is porous and non-protective, whereas when film growth is not limited by mass transport of sulphide, the sulphide film is compact and protective. The results indicate that, under Swedish repository conditions, the film formed on copper will be porous and non-protective and its growth diffusion controlled.

Optical and electrical stability of viral-templated copper sulfide (Cu1.8S) films

The optical and electrical stabilities of viral-templated non-stoichiometric copper sulfide, digenite (Cu1.8S) films were investigated. The films were composed of large agglomerates of randomly aligned Cu1.8S-coated M13 filamentous phage. Free carrier optical absorption associated with localized surface plasmon resonance (LSPR) was observed in the near infrared spectral region, and the films were electrically active, displaying a linear current-voltage relationship. Under ambient conditions, the magnitude of the LSPR absorption increased, following a power law relationship with time, and the electrical resistance of viral-templated films decreased significantly. In contrast, the resistance of films stored under low oxygen, low humidity conditions experienced a smaller reduction in electrical resistance. Changes in optical and electrical film properties under ambient conditions were associated with an increase in free carrier concentration within the copper chalcogenide material due to oxygen exposure. X-ray photoelectron spectroscopy was used to relate this increase in free carrier concentration to compositional changes on the viral-templated material surface.

Mechanisms of Film Growth on Copper in Aqueous Solutions Containing Sulphide and Chloride under Voltammetric Conditions

The electrochemical behavior and film formation mechanisms of oxygen-free copper have been studied in aqueous solutions containing a wide range of sulphide and chloride concentrations using rotating disk electrodes and cyclic voltammetry. Scanning electron microscopy, energy dispersive X-ray spectroscopy and focused ion beam techniques were employed to characterize the morphology, composition and structure of the copper sulphide films formed on the copper surface under voltammetric conditions. These studies show that three distinct type of films were formed depending on the sulphide concentration, the flux of sulphide to the electrode surface, and the chloride concentration of the solution. The properties of the film and the mechanism of growth were determined by competition between sulphide diffusion in solution and the rate of interfacial reactions on the Cu surface. Comparison of these properties of electrochemically grown films to those of films grown under corrosion conditions indicates that pitting should not occur under the conditions expected in a nuclear waste repository.

EFFECT OF CONCENTRATION ON STRUCTURAL AND OPTICAL PROPERTIES OF CUS THIN FILMS

Thin films of Copper sulphide were deposited on gla ss substrates using chemical bath deposition techni que at room temperature from the aqueous solution containing different concentra tion of copper sulphate between 0.05M and 0.15M. Th e effects of the copper concentration of the chemical bath on structural an d optical properties of the amorphous thin film wer e investigated and discussed. The optical absorption and transmission of the thin films were observed between of 330-1100nm taken at room temperature. The optical band gaps of the as-synthesized copper sulp hide thin film for various concentrations were meas ured. The surface morphology has been observed using scanning electron microscop y (SEM) and atomic force microscopy (AFM). The resu lts obtained from AFM demonstrated that the reflectivity was closely rela ted to the surface roughness of the film. High surf ace roughness has a strong scattering effect on light and lowers the reflectiv ity. X-ray diffraction (XRD) patterns show that cry stallinities of the films are dependent on the copper concentration in the soluti on.

The influence of the deposition time on morphological and optical properties of Cu x S films deposited on polypropylene substrate

Copper sulfide (Cu x S) films deposited on polypropylene substrate were obtained by chemical bath deposition (CBD) method. The influence of the deposition time on the morphology of Cu x S films was studied by means of scanning electron microscopy. We have found that the average particles dimension increased from 37 to 49 nm with the increase of deposition time from 20 to 30 minutes. The study of optical properties of the copper sulfide films was carried out based on optical transmission spectra recorded in the 400–1000 nm wavelength range. The optical constants, such as refractive index, extinction coefficient and dielectric constant as well as electrical and optical conductivity of Cu x S films were calculated. The obtained values are in accordance with the ones reported in the literature:We have shown that both, morphological and optical properties of Cu x S films are strongly affected by the deposition time.