Cu2S Layer Research Articles

In Situ Electrochemical Interfacial Manipulation Enabling Lithiophilic Li Metal Anode with Inorganic‐Rich Solid Electrolyte Interphases for Stable Li Metal Batteries

Lithium‐metal anodes (LMAs) are the ultimate choice for realizing high‐energy‐density batteries; however, its use is hindered by problematic Li growth in the form of dendrites. To alleviate dendritic Li growth, the preparation of LMAs with a lithiophilic current collector (CC) is effective; however, applying a lithiophilic CC to LMAs is still challenging due to the manufacturing complexity involved in the separate lithiophilic treatment and lithiation processes. Herein, a facile one‐pot LMA fabrication method by utilizing thiourea (TU) as a precursor is proposed. A lithiophilic Cu2S layer is formed on Cu foam (CF) by the in situ electrochemical oxidation of TU (CuxSCF), and the lithiation of CC is performed via subsequent Li electrodeposition (Li@CuxSCF). The Cu2S on CuxSCF can lead to uniform Li deposition by providing lithiophilic sites, and it is converted to form ionic‐conductive Li2S‐rich solid electrolyte interphase layer. Resultantly, CuxSCF significantly enhances the cycling performance of LMAs compared to CF. Specifically, a LiFePO4/Li@CuxSCF full‐cell lithium‐metal battery (LMB) with a low n/p ratio (1.6) exhibits capacity retention of 95.6% at 0.5 C (220 cycles) and can maintain 85.0% of initial capacity (425 cycles, n/p = 4) at 2.0 C. LMBs with LiNi0.6Co0.2Mn0.2 and LiNi0.8Co0.1Mn0.1 also exhibit improved electrochemical performance.

Asymmetric Copper‐Sulphur Sites Promote C–C Coupling for Selective CO2 Electroreduction to C2 Products

AbstractSustainable multicarbon e‐chemicals are of particular interest due to their potential future, high market values, and demand. In the direct electrocatalytic formation of multicarbon e‐chemicals from CO2, the elementary C–C coupling by CO dimerization is considered the rate‐limiting step. Here, a generalized surface structural design principle of asymmetric metal pair sites is proposed, explored, and experimentally tested in order to promote CO dimerization on surfaces. First a computational model of N‐doped Cu2S layers featuring adjacent, electronically asymmetric Cuδ1+‐Cuδ2+ (0 < δ1+ < δ2+ < 1) metal atomic pairs evidenced by their non‐uniform charge distribution is considered. The electronic asymmetry resulted in distinct CO adsorption energies and the associated self‐adjusting structures, which lowered C–C coupling energy barriers significantly. The computational hypotheses are experimentally tested using X‐ray photoelectron spectroscopy of Cu‐N moieties within N‐doped Cu2S layers. In‐situ Fourier‐transform infrared spectroscopy confirms linear *CO and *CO‐CO adsorption configuration by the peaks of ≈2080 and 1920 cm−1, respectively. After N‐doping, the catalytically C2 faradaic efficiency can significantly be elevated to 14.72% due to the promotion of C–C coupling.

Solution-Processed Cu2S Nanostructures for Solar Hydrogen Production.

Cu2S is a promising solar energy conversion material due to its suitable optical properties, high elemental earth abundance, and nontoxicity. In addition to the challenge of multiple stable secondary phases, the short minority carrier diffusion length poses an obstacle to its practical application. This work addresses the issue by synthesizing nanostructured Cu2S thin films, which enables increased charge carrier collection. A simple solution-processing method involving the preparation of CuCl and CuCl2 molecular inks in a thiol-amine solvent mixture followed by spin coating and low-temperature annealing was used to obtain phase-pure nanostructured (nanoplate and nanoparticle) Cu2S thin films. The photocathode based on the nanoplate Cu2S (FTO/Au/Cu2S/CdS/TiO2/RuO x ) reveals enhanced charge carrier collection and improved photoelectrochemical water-splitting performance compared to the photocathode based on the non-nanostructured Cu2S thin film reported previously. A photocurrent density of 3.0 mA cm-2 at -0.2 versus a reversible hydrogen electrode (V RHE) with only 100 nm thickness of a nanoplate Cu2S layer and an onset potential of 0.43 V RHE were obtained. This work provides a simple, cost-effective, and high-throughput method to prepare phase-pure nanostructured Cu2S thin films for scalable solar hydrogen production.

Crystal Growth and Crystal Structures of Gold(V) Compounds: Cu(AuF6)2, Ag(AuF6)2, and O2(CuF)3(AuF6)4 ⋅ HF

AbstractCrystal growth from anhydrous hydrogen fluoride solutions of M2+(M=Cu, Ag) and [AuF6]−gave M(AuF6)2salts (M=Cu, Ag). Similar attempts to prepare single crystals of the corresponding nickel, zinc and magnesium salts failed. The crystal structure of Cu(AuF6)2consists of layers of Cu2+cations connected by [AuF6]−anions, thus forming slabs. Only van der Waals interactions exist between adjacent slabs. The crystal structure of Ag(AuF6)2consists of a three‐dimensional framework in which Ag+cations are linked by [AuF6]−anions. Both structures are members of the MII(XVF6)2family, in which seven different structure types have been observed to date. In the crystal structure of O2(CuF)3(AuF6)4 ⋅ HF, the bridging AuF6units connect [−Cu−F−Cu−F−]∞chains to form stacks between which O2+cations and HF molecules are located.

Absence of Spin Frustration in the Kagomé Layers of Cu2+ Ions in Volborthite Cu3V2O7(OH)2·2H2O and Observation of the Suppression and Re-Entrance of Specific Heat Anomalies in Volborthite under an External Magnetic Field

We determined the spin exchanges between the Cu2+ ions in the kagomé layers of volborthite, Cu3V2O7(OH)2·2H2O, by performing the energy-mapping analysis based on DFT+U calculations, to find that the kagomé layers of Cu2+ ions are hardly spin-frustrated, and the magnetic properties of volborthite below ~75 K should be described by very weakly interacting antiferromagnetic uniform chains made up of effective S = 1/2 pseudospin units. This conclusion was verified by synthesizing single crystals of not only Cu3V2O7(OH)2·2H2O but also its deuterated analogue Cu3V2O7(OD)2·2D2O and then by investigating their magnetic susceptibilities and specific heats. Each kagomé layer consists of intertwined two-leg spin ladders with rungs of linear spin trimers. With the latter acting as S = 1/2 pseudospin units, each two-leg spin ladder behaves as a chain of S = 1/2 pseudospins. Adjacent two-leg spin ladders in each kagomé layer interact very weakly, so it is required that all nearest-neighbor spin exchange paths of every two-leg spin ladder remain antiferromagnetically coupled in all spin ladder arrangements of a kagomé layer. This constraint imposes three sets of entropy spectra with which each kagomé layer can exchange energy with the surrounding on lowering the temperature below ~1.5 K and on raising the external magnetic field B. We discovered that the specific heat anomalies of volborthite observed below ~1.5 K at B = 0 are suppressed by raising the magnetic field B to ~4.2 T, that a new specific heat anomaly occurs when B is increased above ~5.5 T, and that the imposed three sets of entropy spectra are responsible for the field-dependence of the specific heat anomalies.

Deposition of copper sulfide films on polyamide surface

In this paper, we present a novel and low - cost method for preparing copper sulfide films on polyamide. Non-treated as well as pre-treated PA6 films by 3 different methods (in boiled water; in NaOH solution; in boiled water and then in NaOH solution) were used for the formation of Cu2S layers by the sorption-diffusion method. Molten sulfur has been used as a sulfurization agent. The XRD, FTIR, and UV-VIS methods were used to characterize the structural, optical, and electrical properties of samples and to track changes in samples after each treatment stage. The sheet resistance of Cu2S layers depends on the pre-treatment method and varied from 7 k?/sq to 6 M?/sq. The optical band gaps (Eg) for direct and indirect transitions are determined to be 2.61-2.67 eV and 1.40-1.44 eV, respectively. Furthermore, the optical constants n, k, and ? are determined from UV-VIS measurements.

A Two‐Dimensional Semiconductive Metal‐Organic Framework for Highly Efficient Microwave Absorption

Comprehensive SummaryAdvanced microwave absorbing materials (MAMs) are urgently required to eliminate and attenuate microwaves to address the ubiquitous microwave radiations and interference. In this contribution, we report the microwave absorption application of a two‐dimensional (2D) semiconductive metal‐organic framework (MOF), i.e., CuHT (HT = 4‐hydroxythiophenol), without any pyrolysis at high temperature. Owing to the suitable electrical conductivity (2.69 × 10–4 S·cm–1), CuHT renders remarkable microwave absorption performance, with the minimum reflection loss (RLmin) of –50.9 dB and the effective absorption bandwidth of 4.2 GHz (7.7—10.9 GHz) at a thickness of 1.74 mm. Based on DFT calculation, microwave attenuation is mainly originated from resistance loss due to the conducting planes of honeycomb‐like Cu2S layers. Thanks to the facile kilogram‐scale synthesis, CuHT holds great potential for future microwave absorption applications.

Hydrothermal Synthesis and a Composite Crystal Structure of Na6Cu7BiO4(PO4)4[Cl,(OH)]3 as a Candidate for Quantum Spin Liquid

A novel sodium bismuth oxo-cuprate phosphate chloride, Na6Cu7BiO4(PO4)4[Cl2.23(OH)0.77], containing square-kagomé layers of Cu2+ has been synthesized by hydrothermal techniques. The compound crystallizes in the tetragonal space group P4/nmm, a = 10.0176(4), c = 10.8545(6), Z = 2, V = 1089.3(1) Å3, R1 = 0.021, wR = 0.053, S = 1.32. Its composite crystal structure includes [O4Cu6Bi]7+ layers, which are formed by the clusters of oxygen-centered tetrahedra [OCu3Bi]. These positively charged two periodic fragments are intercalated in a negatively charged [CuNa6Cl3(PO4)4]7- matrix built by Na-centered polyhedra, PO4 tetrahedra, and CuO4Cl pyramids. The composite character of the crystal structure of Na6Cu7BiO4(PO4)4[Cl2.23(OH)0.77], as well as the way of its self-assembly, are discussed in close connection with the sulfohalite Na6ClF(SO4)2 salt. It is shown that the "host-guest" model of the formation of the tetragonal Na6Cu7BiO4(PO4)4[Cl2.23(OH)0.77] phase is due to the group-subgroup symmetry relation with the cubic crystal structure of mineral sulfohalite and is also supported by the crystallization condition in excess sodium chloride. The magnetic subsystem of Na6Cu7BiO4(PO4)4[Cl2.23(OH)0.77] is represented by a dense square-kagomé network of 2Cu1 and 4Cu2 ions, decorated with weakly bonded Cu3 ions. Measurements of magnetization and heat capacity indicate the absence of long-range order up to 2 K, which makes this compound a candidate for a highly demanded spin liquid.

Atomic-level insights into the activation of nitrogen via hydrogen-bond interaction toward nitrogen photofixation

Summary As the activation of N2 molecules is generally regarded as the bottleneck in N2 reduction, it is of significant importance to develop promising strategies to efficiently activate N2 molecules. Herein, we discovered an innovative approach to activate N2 molecules via hydrogen-bond interaction in N2 photofixation. Porous Cu with surface modification of S atoms (3%-S/Cu) exhibited remarkable catalytic activity and stability in N2 photofixation. Further mechanistic studies revealed that surface S atoms directly participated in the catalytic process by accepting and donating H atoms. In addition, the forming S–H bond significantly promoted the activation of N2 molecules via hydrogen-bond interaction, contributing to the enhanced catalytic activity.

Investigation of the selectivity-mechanism of copper (I) sulfide (Cu2S) as a dopant-free carrier selective contact for silicon solar cells

Carrier selective contacts based on dopant free materials are receiving increased attention. Copper(I) sulfide (Cu2S), earth-abundant and non-toxic, shows potential for use in silicon (Si) solar cells, though its carrier selectivity mechanism remains unclear. We present a detailed investigation of the selectivity mechanisms behind thermally evaporated Cu2S on Si. Deposited Cu2S layers are studied by X-ray photoelectron spectroscopy, Auger electron spectroscopy, X-ray diffraction and UV/VIS (ultraviolet–visible) methods. From X-ray photoelectron spectroscopy and Auger electron spectroscopy, only sulfur related Cu(I) bonds are observed in the deposited film. X-ray diffraction measurements indicate that Cu1.95S (djurleite) may also exist in the film. The indirect and direct bandgaps are determined to be 1.2 eV and 2.2 eV, respectively. Band bending of ~0.6 eV is calculated for Cu2S/n-Si (~5 Ω·cm), while it is significantly lower (~0.07 eV) for Cu2S/p-Si (~2.25 Ω·cm). Current-voltage measurements indicate that the carrier selectivity originates from an induced junction at the Cu2S/n-Si interface, and not from a large band-offset of the conduction band. The Cu2S/p-Si structure displays no carrier selectivity, a finding attributed to the insufficient band bending at the interface.

From magnetic order to quantum disorder in the Zn-barlowite series of S\u2009=\u20091/2 kagom\xe9 antiferromagnets

We report a comprehensive muon spectroscopy study of the Zn-barlowite series of S=frac{1}{2} kagomé antiferromagnets, ZnxCu4−x(OH)6FBr, for x = 0.00 to 0.99(1). By combining muon spin relaxation and rotation measurements with state-of-the-art density-functional theory muon-site calculations, we observe the formation of both μ–F and μ–OH complexes in Zn-barlowite. From these stopping sites, implanted muon spins reveal the suppression of long-range magnetic order into a possible quantum spin liquid state upon the increasing concentration of Zn-substitution. In the parent compound (x = 0), static long-range magnetic order below TN = 15 K manifests itself in the form of spontaneous oscillations in the time-dependent muon asymmetry signal consistent with the dipolar fields expected from the calculated muon stopping sites and the previously determined magnetic structure of barlowite. Meanwhile, in the x = 1.0 end-member of the series—in which antiferromagnetic kagomé layers of Cu2+S=frac{1}{2} moments are decoupled by diamagnetic Zn2+ ions—we observe that dynamic magnetic moment fluctuations persist down to at least 50 mK, indicative of a quantum disordered ground state. We demonstrate that this crossover from a static to dynamic magnetic ground state occurs for compositions of Zn-barlowite with x > 0.5, which bears resemblance to the dynamical behaviour of the widely studied Zn-paratacamite series that contains the quantum spin liquid candidate herbertsmithite.

Facile one-step vulcanization of copper foil towards stable Li metal anode

Lithium metal has been regarded as the ultimate anode for next-generation rechargeable batteries with high energy density. However, its high reactivity and dendrite growth seriously limit its commercial application, which can be well addressed by realizing uniform Li deposition. Here, we report a facile and scalable one-step vulcanization method to modify commercial Cu foil with lithophilic Cu2S. The in situ formed Cu2S layer can not only promote the homogeneous deposition of Li via its lithophilic nature, but also benefit the formation of a stable solid-electrolyte interphase during initial activation. The Cu2S-modified Cu current collector realizes dendrite-free Li plating/stripping and thus exhibits stable cycling performance with a high Coulombic efficiency, even with a large capacity of 4 mA h cm−2. A full-cell consisting of a Cu2S/Cu-Li anode and a LiFePO4 cathode exhibits greatly improved cycling stability and enhanced Coulombic efficiency, demonstrating the effectiveness and practicability of the proposed Cu2S/Cu foil in the field of rechargeable Li metal batteries.

Simultaneous etching of underlying metal oxide and sulfide thin films during Cu2S atomic layer deposition

Herein, we report the simultaneous etching of selected metal oxide and sulfide underlayers during the atomic layer deposition (ALD) of Cu2S. The unexpected etch was observed to be prompted by the infiltration of highly mobile Cu+ ions from a top ALD Cu2S layer into underlying films, followed by fragmentation of the underlayers and subsequent outward diffusion of both cations and anions from the underlayers to the Cu2S surface. A strong correlation was observed between the susceptibility to etching, etch rates and the bond dissociation energies of the underlayers. ZnS, ZnO, SnS, and SnO thin films were etched at different rates, while SnO2 exhibited high resistance to etching. Interestingly, the etch process exhibited self-limiting characteristics dependent on the Cu precursor and H2S gas dose times, thus indicating simultaneous Cu2S ALD and controlled sublayer etching reactions. Based on the findings, we proposed a possible mechanism by which the etching proceeds. We further explored, the synthesis of 3-dimensional Cu2S/ZnO and Cu2S nanowires using ALD Cu2S and the observed ZnO etching phenomenon.

Fabrication and Characterization of Poly(aniline-co-4-bromoaniline)/Сlay Nanocomposite

Poly(aniline-co-4-bromoaniline) nanocomposites were prepared via in situ polymerization in different molar ratio in the presence of Cu2+−monmorillonite. The X-ray diffraction confirmed that the basal space of Cu2+−montmorillonite increased after the organophilization. Poly(aniline-co-4-bromoaniline)/Cu2+−monmorillonite nanocomposites were prepared by intercalating of aniline and 4-bromoaniline with treated organically layers of Cu2+−monmorillonite following by polymerization initiated by ammonium peroxdisulfate. The nanocomposites were characterized by FTIR, XRD, and UV–Vis spectroscopy.

Efficient silicon solar cells applying cuprous sulfide as hole-selective contact

The introduction of dopant-free materials used for carrier-selective contact effectively overcomes the issue of high surface recombination velocity at aluminum back surface field. Additionally, dopant-free materials have the advantages of low fabrication temperature, simple process and considerably high efficiency. In this contribution, cuprous sulfide (Cu2S), fabricated by thermal evaporation, is applied as hole-selective contact material at rear-surface region of crystalline silicon (c-Si) solar cells for the first time. The band alignment of Cu2S/p-Si exhibits only a small valence band offset and huge conduction band offset being excellent hole-selective and electron blocking properties. By inserting Cu2S layer between p-Si and Ag, a lower contact resistivity of 27.2 mΩ cm2 is achieved. As a result, the introduction with 4-nm Cu2S interlayer significantly improves device efficiency to over 21%, affording a 1.2% absolute increase from the control cell. Metal sulfides introduced herein exhibit remarkable properties for carrier-selective contacts, compared to conventional metal nitrides and oxides.

Investigation on the formation process of metal atomic filament for metal sulfide atomic switches by electrical measurement

We have studied the formation process of the metal atomic filament for metal sulfide atomic switches by electrical measurement. The switching between ON and OFF states of the atomic switch is controlled by the application of the bias voltage for the atomic switches. The SET (OFF → ON) and RESET (ON → OFF) voltages were investigated for the atomic switch where the Ag2S or Cu2S layer were sandwiched between the Pt and Ag or Cu electrodes. The SET and RESET voltages of the Ag/Cu2S/Pt and Cu/Ag2S/Pt were close to those of the Ag/Ag2S/Pt atomic switch, and different from those of the Cu/Cu2S/Pt atomic switch. These results indicated that the dominant chemical species of the making and breaking part of the metal filament was Ag, and that the source of the metal filament was both the sulfide layer and the metal electrode.

Semiconductor Plasmonic Nanocrystals with a Near-Infrared Localized Surface Plasmon Resonance

The techniques of preparation of layers of Cu2 – xSe semiconductor plasmonic nanocrystals (SPNC) with plasmonic resonances in near infrared region from toluene colloidal solution are described. It is shown that combining QDs with SPNC layers lead to the enhancement of optical response from the QDs. The PVA film makes it possible to optimize the QDs-SPNC interlayer distance and provide most efficient enhancement.

Kinetic Properties of the Passive Film on Copper in the Presence of Sulfate-Reducing Bacteria

Copper specimens were exposed to Sulfate-Reducing Bacteria (SRB) for 10 months under the conditions corresponding to the final disposal of high-level nuclear waste. In-situ electrochemical impedance spectroscopy (EIS) measurements were carried out to characterize the surface-environment interface after various times of exposure. The EIS results are interpreted in terms of the Point Defect Model (PDM), in order to obtain kinetic information on the formation of the Cu2S passive film. The standard rate constant and the rate constants for the surface reactions revealed that the Cu2S layer is a p-type semiconductor. The diffusion constant for cation vacancies in the barrier layer and the average bulk cation vacancy concentration in the barrier layer were found to be on the orders of 10−13 cm2⋅s−1 and 1022 cm−3, respectively, i.e., both slightly higher than reported in literature for corresponding electrochemically developed Cu2S layers. The electric field strength was approximately 3⋅105 Vcm−1 at all measurement points. These results are presented and discussed in this work in the light of storage of high-level nuclear waste.

Communication—Electrochemical Atomic Layer Etching of Copper

A novel process for the electrochemical atomic layer etching (e–ALE) of copper (Cu) is presented. In this process, Cu first undergoes surface-limited sulfidization to form a monolayer of copper sulfide (Cu2S). The Cu2S layer is then selectively etched in hydrochloric acid without etching the underlying Cu. The steps of surface-limited sulfidization of Cu and selective etching of the resulting Cu2S are repeated sequentially to achieve a net etch rate of close to one Cu monolayer etched per e–ALE cycle. Surface-limited etching is shown to minimize roughness amplification thereby preserving the near-atomic flatness of the original Cu electrode.

Reclaiming the image of daguerreotypes: Characterization of the corroded surface before and after atmospheric plasma treatment

Technological developments such as atmospheric plasma jets for industry can be adapted for the conservation of cultural heritage. This application might offer a potential method for the removal or transformation of the corrosion on historical photographs. We focus on daguerreotypes and present an in-depth study of the induced changes by a multi-analytical approach using optical microscopy, scanning electron microscopy, different types of transmission electron microscopy and X-ray absorption fine structure. The H2-He afterglow removes S from an Ag2S or Cu2S layer which results in a nano-layer of metallic Ag or Cu on top of the deteriorated microstructure. In case the corrosion layer is composed of Cu-Ag-S compounds, our proposed setup can be used to partially remove the corrosion. These alterations of the corrosion results in an improvement in the readability of the photographic image.