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CuFeS2 (CFS) stands out as a promising narrow band-gap semiconductor for thermoelectric (TE) applications. However, its high lattice thermal conductivity is one of the factors hampering its potential for TE generation. A common strategy for tackling this problem is to produce this material in thin film form. Thus, this study aims to practically understand and optimize the synthesis of CFS 2D materials using a simple three-step approach of ball-milling, thermal evaporation, and sulfurization of the CuFe metallic precursors. The tools for thin film characterization employ X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDXS), and Hall-effect measurements. DFT phase diagrams are also used to understand the energy of formation of the secondary phases present in the film. Here, we highlight that the ball-milling mechanisms, allied with high vacuum and high energy density during evaporation, are essential for the interdiffusion of Cu and Fe during the evaporation process. The film presented a flower-like morphology and p-type semiconducting behavior. A proof-of-concept Thermoelectric Generator (TEG) was designed in an in-plane geometry, showing a power output per unit active area of 114 nW cm−2 (ΔT = 180 °C), comparable to other Cu-based materials, thus demonstrating the feasibility of this method of synthesis for TE applications. [ABSTRACT FROM AUTHOR]

Nano-structure designs with conductive networks have been demonstrated as an efficient strategy to boost sodium storage properties for transition metal sulfides. Herein, an exquisite nanosheets self-assembled hierarchical flower-ball-like CuFeS2 embedded into the reduced graphene oxide (RGO) nanosheet matrix (F-CuFeS2@RGO) is fabricated via a concise two-step solvothermal method. Such a well-designed architecture affords increased active reaction interfaces and enhanced mixed ionic/electronic conductivity. Meanwhile, the external RGO matrix can effectively alleviate the volume expansion and create a stable structure during long cycles. As a result, the composite material exhibits a high reversible capacity of 559 mAh·g−1 at 0.1 A·g−1, a superior rate capability of 455 mAh·g−1 at 5 A·g−1 and excellent cyclic stability with 96% capacity retention after 4800 cycles at 5 A·g−1, among the best in the state-of-the-art transition metal sulfide anodes. Especially, F-CuFeS2@RGO delivers outstanding low-temperature performances with a high capacity retention of 100% and 91% at −20 and −40 °C, respectively, over 200 cycles. The proposed hierarchical structure fabrication paves a new direction in the design of high-performance electrodes for all-temperature energy storage applications. [ABSTRACT FROM AUTHOR]

Transition metal sulfides are widely employed as bifunctional electrocatalysts owing to their unique structural features, well-off active sites, and modifiable electronic and mechanical properties. Herein, we have synthesized highly efficient ternary copper iron sulfide (CuFeS2)/reduced graphene oxide (rGO) composites via a hydrothermal approach for an overall water splitting process. The tetragonal structure of CuFeS2 microflowers anchored on rGO sheets is identified by using X-ray analysis and compared with standard Joint Committee on Powder Diffraction Standards (JCPDS) #35-752. In Raman spectra, the existence of two bands D (defects) and G (graphitic) confirms the presence of the rGO composite with CuFeS2, and the ratio of D and G band (ID/IG) is observed to be 1.18. The morphological analysis using scanning electron microscopy and transmission electron microscopy substantiates the formation of microflowers with rGO sheets. The elemental composition of CuFeS2/rGO was analyzed by energy-dispersive X-ray analysis, which demonstrated a weight percentage of various compositions of Cu (18.07%), Fe (11.32%), S (13.88%), and C (56.74%). Moreover, the CuFeS2/rGO composites exhibited a high surface area, pore volume, and diameter of 50.352 m2/g, 0.162 cc/g, and 2.471 nm, respectively. The fabricated electrodes were examined by using electrochemical characterization. The obtained results clearly showed low overpotential and low Tafel slope values in both the oxygen evolution reaction (OER) (176 mV and 216 mV/dec) and hydrogen evolution reaction (HER) (153 mV and 150 mV/dec) processes. In addition, the fabricated composite exhibited low 1.59 V cell voltages for an overall water splitting process with more excellent stability, and it showed a faradaic efficiency of 97.8% for H2 and 95.5% for O2. Therefore, the composite of rGO in ternary metal sulfide plays a predominant role in improving the electrocatalytic activity of the material, and the CuFeS2/rGO composite emerges as a promising electrode for the water splitting process. [ABSTRACT FROM AUTHOR]

Abstract In this paper, on the basis of first-principles, the CASTEP module of Materials Studio is used to calculate the band structures and optical properties of CuFeSe2 and CuFeS2 under the PBE pseudopotential of the generalized gradient approximation (GGA). The calculated results show that both CuFeSe2 and CuFeS2 are direct bandgap semiconductors with forbidden band widths of 0.64 eV and 1.06 eV, respectively. In the visible light range, the highest absorption coefficient of CuFeSe2 is 1.082×105 cm-1, the average reflectivity is 0.52, the maximum conductivity is 7.23 fs-1, the electrostatic constant is 65.9; the maximum value the highest absorption coefficient of CuFeS2 is 0.872×105 cm-1, the average reflectivity is 0.44, the maximum conductivity is 4.44 fs-1, the static dielectric constant is 52.32. The calculation results in this paper show that compared with CuFeS2, CuFeSe2 has advantages in photoconductivity and carrier separation, but has disadvantages in band gap and reflectivity. It is recommended to combine the two materials to prepare tandem solar cells.

In this study, chalcopyrite (CuFeS2), a natural mineral with a bimetallic structure, was used as the activator to generate radicals for removing organic pollutants from aqueous solutions via the activation of peroxymonosulfate (PMS). Sulfisoxazole (SIX), a sulfonamide antibiotic, was selected as the model pollutant. The results showed that chalcopyrite was highly reactive toward the activation of PMS; under the conditions of 50 µM PMS and 1 g/L chalcopyrite, approximately 95.7% of the SIX was degraded after reaction for only 5 min. An increase in the loading of chalcopyrite (0.25–2 g/L) promoted the degradation of SIX, while elevated levels of PMS (0.05–0.5 mM) slightly retarded the degradation kinetics. Although the best performance was observed under acidic conditions (pHs 3 and 4), near complete degradation of SIX was also achieved at pH 5.5. Identification of reactive species revealed that both a hydroxyl radical and a sulfate radical were formed in chalcopyrite–PMS oxidation, and they were responsible for the degradation of SIX. Trace amounts of copper and iron were leached out from chalcopyrite during the activation, and both the heterogeneous and homogeneous activation of PMS contributed to the generation of oxidizing radicals. Common water constituents including Cl−, HCO 3 − , and natural organic matter at their environmentally relevant levels showed a limited effect on the degradation of SIX, which suggests that chalcopyrite–PMS oxidation has high reactivity and stability in the degradation of organic pollutants and shows great practical application potential. [ABSTRACT FROM AUTHOR]

Bulk and nanoparticles of n -type CuFeS 2 Chalcopyrite have been synthesized using vacuum melting reaction and conventional hydrothermal method, respectively. The powder XRD pattern of both the samples has confirmed phase formation, and the crystallite size was calculated to be ∼30 nm for nano-CuFeS 2. FE-SEM micrographs illustrate the cuboid morphology of nano-CuFeS 2 with particles sizes in the range of 50–200 nm, and EDS analysis confirms the nominal composition. The elemental composition and electronic states of Cu1+, Fe3+, and S2− present in CuFeS 2 are further confirmed by XPS studies. The weak ferromagnetic nature of both bulk and nano-CuFeS 2 with magnetic saturation of ∼0.075 emu/g and ∼0.036 emu/g, respectively, has been observed from VSM measurements. The bulk n -type CuFeS 2 exhibits the Seebeck coefficient of −160 μV/K at room temperature, increasing to −187 μV/K for nano-CuFeS 2. Interestingly, a huge reduction in total thermal conductivity of ∼0.69 W/mK is observed in nano-CuFeS 2 compared to the bulk sample (∼4.18 W/mK) at room temperature, resulting in an overall enhanced thermoelectric figure of merit, zT of ∼0.28 at 623 K for nano-CuFeS 2. Mid-to-long wavelength phonon scattering from the increased grain boundaries and reduced grain sizes of nano-CuFeS 2 and their corresponding reduction in lattice thermal conductivity as a function of temperature. [Display omitted] • Bulk and nano CuFeS 2 samples have been successfully synthesized using vacuum melting and hydrothermal method, respectively. • The mean particle size of nano-CuFeS 2 was calculated to be ∼130 nm. • An increase in Seebeck co-efficient (S) of −305 μV/K at 623 K was observed for nano-CuFeS 2. • Ultra-low thermal conductivity of ∼0.69 W/mK at 623 K was observed for nano-CuFeS 2. • Overall, a maximum figure of merit (zT) of 0.28 at 623 K is achieved for nano-CuFeS 2. [ABSTRACT FROM AUTHOR]

CuFeS2/TiO2 nanocomposite has been prepared by a simple, low-cost mechanochemical route to assess its visible-light-driven photocatalytic efficiency in Methyl Orange azo dye decolorization. The structural and microstructural characterization was studied using X-ray diffraction and high-resolution transmission electron microscopy. The presence of both components in the composite and a partial anatase-to-rutile phase transformation was proven by X-ray diffraction. Both components exhibit crystallite size below 10 nm. The crystallite size of both phases in the range of 10–20 nm was found and confirmed by TEM. Surface and morphological properties were characterized by scanning electron microscopy and nitrogen adsorption measurement. Scanning electron microscopy has shown that the nanoparticles are agglomerated into larger grains. The specific surface area of the nanocomposite was determined to be 21.2 m2·g−1. Optical properties using UV-Vis and photoluminescence spectroscopy were also investigated. CuFeS2/TiO2 nanocomposite exhibits strong absorption with the determined optical band gap 2.75 eV. Electron paramagnetic resonance analysis has found two types of paramagnetic ions in the nanocomposite. Mössbauer spectra showed the existence of antiferromagnetic and paramagnetic spin structure in the nanocomposite. The CuFeS2/TiO2 nanocomposite showed the highest discoloration activity with a MO conversion of ~ 74% after 120 min irradiation. This study has shown the possibility to prepare nanocomposite material with enhanced photocatalytic activity of decoloration of MO in the visible range by an environmentally friendly manner [ABSTRACT FROM AUTHOR]

CuFeS2 (CFS) stands out as a promising narrow band-gap semiconductor for thermoelectric (TE) applications. However, its high lattice thermal conductivity is one of the factors hampering its potential for TE generation. A common strategy for tackling this problem is to produce this material in thin film form. Thus, this study aims to practically understand and optimize the synthesis of CFS 2D materials using a simple three-step approach of ball-milling, thermal evaporation, and sulfurization of the CuFe metallic precursors. The tools for thin film characterization employ X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDXS), and Hall-effect measurements. DFT phase diagrams are also used to understand the energy of formation of the secondary phases present in the film. Here, we highlight that the ball-milling mechanisms, allied with high vacuum and high energy density during evaporation, are essential for the interdiffusion of Cu and Fe during the evaporation process. The film presented a flower-like morphology and p-type semiconducting behavior. A proof-of-concept Thermoelectric Generator (TEG) was designed in an in-plane geometry, showing a power output per unit active area of 114 nW cm−2 (ΔT = 180 °C), comparable to other Cu-based materials, thus demonstrating the feasibility of this method of synthesis for TE applications.

As an anode in sodium-ion batteries (SIBs), chalcopyrite (CuFeS2) has aroused tremendous interest owing to its earth-abundant elements and high theoretical specific capacities. Because ingenious nanostructures of electrode materials can significantly improve their energy storage properties, in this paper, CuFeS2 nanosheets have been assembled into honeycomb-like microspheres by a facile solvothermal method. The performance of the CuFeS2 product with the honeycomb-like microsphere structure is analyzed by several physicochemical characterizations. The results indicate that the microsphere structure of CuFeS2 can improve the energy storage properties of the anode material when it is used in SIBs. Specially, the reversible capacity is up to 528 mA h g–1 after 100 cycles, over 86.4% of initial capacity retentions, and an excellent cycling stability is achieved. Moreover, the CuFeS2 microsphere can buffer the volume expansion due to the unique layer structure. Therefore, CuFeS2 nanosheet-assembled honeycomb-like microspheres can significantly improve the energy storage properties of electrode materials during the discharging and charging processes, and it shows great promise to become the next-generation electrode material for large-scale energy storage. [ABSTRACT FROM AUTHOR]

This work reports one-pot solvothermal synthesis of CuFeS2 nanomaterial using Cu(NO3)2•6H2O and FeCl2(3-Cl-benztsczH)2, where benztsczH = benzaldehyde thiosemicarbazone as molecular precursors. The electrochemical performance of as-prepared chalcopyrite, CuFeS2 nanomaterial was studied in order to investigate its ability to work as a supercapacitor material for energy storage devices. The material obtained was characterized by various techniques. The XRD pattern of as-prepared chalcopyrite, CuFeS2 matches with tetragonal phase of the material (JCPDS card no. 037–0471). The crystallite size calculated using Scherrer's formula is found to be 41.5 nm. High resolution transmission electron microscopy (HRTEM) revealed the presence of nanomaterial having spherical morphology. The electrochemical properties of the as-prepared chalcopyrite, CuFeS2 electrode were investigated in aqueous electrolyte, 6 M KOH. Cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) curves show the pseudocapacitive behaviour of the CuFeS2 electrode. The material is found to have excellent specific capacitance of 206.3 C g−1 (589 F g−1) at 0.5 A g−1 current density with cycle stability of ∼82% after 2000 cycles (at current density of 4 A g−1).

In this research work, high uniform CuFeS2 chalcopyrite with 20-40 nm particles were synthesized via a simple hydrothermal method. Different analysis were used to characterize the obtained product such as X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermal gravimetric analysis (TGA). The photocatalytic activity of the product was investigated by degradation three different dyes namely acid brown, acid red and methylene blue. The results showed the synthesized CuFeS2 nanoparticles have high photocatalytic activity and can degrade the used dyes in large quantities.

Four chalcopyrite (CuFeS 2) catalysts were fabricated by a hydrothermal method using different copper and iron precursors at different valence states. The prepared CuFeS 2 samples were then evaluated for the oxidative degradation of Congo red (CR) using sodium percarbonate (SPC) as the oxidant. The sample of CuFeS 2 -1, which was prepared from Cu (I) and Fe (II) precursors, exhibited the highest CR removal efficiency of 96.6% among the four CuFeS 2 samples. Using CuFeS 2 -1 as the optimum catalyst, the effects of operation and environmental factors on the removal efficiency of CR were investigated in detail. Mechanism studies showed that CO 3 •− was the main reactive oxidative species in the reaction process, while O 2 •− and low-valent sulfur species together promoted the regeneration of Fe (II) and Cu (I) sites on the catalyst. Furthermore, density functional theory (DFT) calculations were used in combination with liquid chromatography-mass spectrometer (LC-MS) to propose the plausible degradation pathway. Finally, toxicity prediction showed that most of the degradation products showed decreased toxicity compared to the parent CR, and toxicity evaluation with Vigna radiata further revealed the declined toxicity. [Display omitted] • Four CuFeS 2 catalysts prepared from metal precursors at different valence states. • The catalysts were used to activate SPC for degradation of organic pollutants. • The one obtained from Cu(I) and Fe(II) showed the best catalytic performance. • CO 3 •− and O 2 •− were involved in the catalytic oxidation process. • The degradation pathway of CR was proposed with the assistance of DFT calculations. [ABSTRACT FROM AUTHOR]

In recent years, CuFeS2 optoelectronic materials are widely concerned by scientists because of their advantages of safety, non-toxicity and low price. In this work, the CuFeS2 powders were synthesized by simple hydrothermal co-reduction method, the effects of different heat treatment conditions and different sulfur sources on preparation of CuFeS2 phase were systematically studied with CuCl2·2H2O and FeCl3·6H2O as raw materials. The phase structure and surface morphology of the samples were analyzed by X-ray Powder diffractometer (XRD) and scanning electron microscope (SEM). It was found that when the sulfur source was sulfur powder, the sample crystallized well and has no impurity formation. With the reaction temperature extending to 220 °C, the diffraction peak intensity is obviously improved while the grain size decreases slightly with the increase of temperature. The extension of heat treatment temperature and holding time is favorable for preparation of CuFeS2 power and the impurity Fe3O4 crystal can be effectively eliminated by prolonging the time and increasing temperature. With the reaction temperature extending to 220 °C, the shorter the time required for Fe3O4 crystal to disappear. Therefore, the optimum heat treatment temperature for preparing CuFeS2 powder is 220 °C and the time is 20 h. [ABSTRACT FROM AUTHOR]

In this research work, high uniform CuFeS2 chalcopyrite with 20-40 nm particles were synthesized via a simple hydrothermal method. Different analysis were used to characterize the obtained product such as X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermal gravimetric analysis (TGA). The photocatalytic activity of the product was investigated by degradation three different dyes namely acid brown, acid red and methylene blue. The results showed the synthesized CuFeS2 nanoparticles have high photocatalytic activity and can degrade the used dyes in large quantities. [ABSTRACT FROM AUTHOR]

Since Cu2+ and Fe3+ ions have been considered as bioactive cations in oxygen transport and enzymatic reactions, the development of reliable ways for the monitoring of the two species will be highly desirable. But the optical stability of conventional organic chromophores needs to be improved. Therefore, the employment of quantum dots (quantum dots are abbreviated to be QDs) such as ternary CuFeS2 QDs for the purpose of sensing has been reported in this study. CuFeS2 QDs were synthesized by using oleylamine as the stabilizer at 180 °C and the particle size was around 2–3 nm. The monodispersed quantum dots with tetragonal chalcopyrite crystalline structure were identified. The corresponding excitation and emission wavelengths of the QDs were monitored at 372 and 458 nm. Magnetic properties were analyzed via applied magnetic field ranging between −6000 and 6000 Oe at 300 K and the ferromagnetic phase was verified. In this report, CuFeS2 QDs has been used as an optical probe to detect the metal ions with high sensitivity, selectivity and fast responses. Two linear equations can be obtained in the range from 0 to 30 μM for Cu2+ and from 0 to 45 μM for Fe3+ (detection limits: Cu2+, 1.98 μM; Fe3+, 2.15 μM). These results may provide promising applications in cation sensing fields. [ABSTRACT FROM AUTHOR]

• CuFeS 2 exhibited a good performance for activated peroxymonocarbonate (APMC) process. • CuFeS 2 showed reversible redox properties and iron acted as catalytic active sites. • HCO 3 − rather than H 2 O 2 greatly influenced the performance of APMC process. • Al 2 O 3 -supported CuFeS 2 was effective and safe when used as fillers for APMC process. Recently, increasing attention has been paid to the activated peroxymonocarbonate (APMC) process, because it is envisioned to be engineered for the chemical oxidation remediation of groundwater in karstic regions with elevated levels of naturally occurring bicarbonate. In the present study, we explored the feasibility of using metal sulfides (CuFeS 2 , CuS, and FeS 2) as the catalysts for heterogeneous APMC (H-APMC) processes. Among the three synthesized metal sulfides, the CuFeS 2 catalyst exhibited reversible redox properties, thereby it had the best performance to activate peroxymonocarbonate (PMC) for the degradation of 2,4-dichlorophenol (2,4-DCP). The X-ray photoelectron spectroscopy analysis and density-functional-theory calculations both revealed that, for the CuFeS 2 -catalyzed APMC process, iron sites of CuFeS 2 acted as the catalytic active sites. Electron spin resonance and chemical quenching experiments revealed that the intermediated reactive species for a CuFeS 2 -catalyzed APMC process included hydroxyl radicals (OH), singlet oxygen (1O 2), superoxide radicals (O 2 −), and carbonate radicals (CO 3 −). It was also found that, under a low bicarbonate condition (≤25 mM), the concentration of H 2 O 2 was not the limiting factor that controlled the degradation rate of 2,4-DCP. Instead, bicarbonate concentration and catalyst dosage significantly influenced the performance of CuFeS 2 -catalyzed APMC process. Al 2 O 3 -supported CuFeS 2 catalyst (Al 2 O 3 @CuFeS 2) was prepared and tested as fillers for practical application. The flowing experiment using fixed-bed reactor showed that the Al 2 O 3 @CuFeS 2 fillers could effectively activate PMC and thereby degraded the 2,4-DCP. Runoff of the coated CuFeS 2 component occurred during the experiment, but the leached copper and iron species from the fillers were constantly at a low and safe level (<1.5 mg/L). The CuFeS 2 -catalyzed APMC process showed a good prospect for groundwater remediation in karstic regions. [ABSTRACT FROM AUTHOR]

Multimodal therapy is an emerging medical intervention to overcome the current limitation in cancer therapy combining treatment modalities with different mechanisms of action to eradicate tumors. This study demonstrates a targeted multifunctional bovine serum albumin (BSA)-functionalized CuFeS 2 /chlorin e6 (Ce6) for synergistic photothermal therapy (PTT) and photodynamic therapy (PDT) effects. The CuFeS 2 nanocrystals were synthesized through a simple heating-up approach and transferred into an aqueous phase using BSA in an ultrasonic-assisted microemulsion method. The as-prepared CuFeS 2 @BSA nanoparticles further conjugated with folic acid (FA) followed by attachment of Ce6 to form the Ce6:CuFeS 2 @BSA-FA nanohybrid with improved solubility and strong near-infrared (NIR) absorbance and fluorescence. It is the first report to fabricate the targeted Ce6:CuFeS 2 @BSA-FA hybrid and evaluates their synergistic PTT/PDT effect using a single laser. The Ce6:CuFeS 2 @BSA-FA hybrid showed lower toxicity in vitro (HeLa and HepG2 cells) and in vivo (zebrafish embryos), while they are selectively recognized and internalized by HeLa cells that over-express folate receptors. Compared to each modality applied separately, the combined single-laser-induced PTT and PDT treatment showed the enhanced generation of heat and reactive oxygen species (ROS) with synergistic cancer killing under 671 nm laser irradiation (10 min, 1 W/cm2). As a biocompatible targeted nanoprobe, the multifunctional nanohybrid holds promise in combined PDT/PTT synergistic therapy to achieve better efficacy. Unlabelled Image • A therapeutic agent was constructed by integrating Bovine serum albumin functionalized CuFeS 2 with chlorin e6 and folic acid. • In vitro and in vivo experiments show low systemic cytotoxicity and remarkable biocompatibility. • Upon irradiation with a single laser, nanohybrid exhibits synergistic photothermal and photodynamic therapy effect. [ABSTRACT FROM AUTHOR]

Semiconducting CuFeS2 with a diamond-like structure has been recently studied as a potential candidate for thermoelectric applications. In the present study, Pd substitution for Cu was examined in terms of thermoelectric properties. A series of Pd-doped Cu1−xPdxFeS2 (x = 0-0.1) samples were synthesized. The thermoelectric and transport properties of hot-pressed sample pellets were characterized. We observed three effects: (1) Pd substituted for Cu behaves as an effective donor, increasing the free electron concentration. (2) Formation of the foreign phase—PdS—was observed above the solubility limit of Pd in CuFeS2 (x ≥ 0.02). (3) Segregation of the foreign phase is accompanied by the formation of FeCu2+ antisite defects. All these effects synergically enhanced both the power factor S2·σ and the thermoelectric parameter ZT. The highest values of the power factor (∼ 1 mW m−1 K−1) and the ZT parameter (∼ 0.19 at 573 K) were achieved in the Cu0.9Pd0.1FeS2 sample. [ABSTRACT FROM AUTHOR]

Abstract We report the first use of a CuFeS 2 froth flotation mineral concentrate (MC) as an energy storage material in a fixed bed flow cell (FBFC). The performance of a graphite felt (GF) MC negative electrode (GF–MC) was also compared to a synthetic CuFeS 2 electrode in the same FBFC. The Fe(II)/Fe(III) redox reaction (in the presence of Cu(II)) on the GF positive electrode (GF–Fe/Cu) supported the charge/discharge process. The kinetic parameters calculated from individual cyclic voltammetry scans of negative and positive electrodes revealed that the electrochemical processes in the FBFC were quasi-reversible. In cell C–1 (GF–CuFeS 2 /GF–Fe/Cu), a continuous increase in specific capacity (∼9–48 mAh g−1) and energy (2–6.3 Wh kg−1) in 500 charge/discharge cycles was attributed to the capacitive behavior of the S 2 2−/S2− species present on the CuFeS 2. However, during 400 GCD cycles of C–2 (GF–MC/GF–Fe/Cu), a monotonic increase in the specific capacity (20–49 mAh g−1) and energy (3.5–8.5 Wh kg−1) was associated with an additional capacitive response from FeS 2 in the MC. Advantageously, 10.3 and 12.7% Cu was also extracted from the C–1 and C–2 cells, respectively, which is unique to this system and provides a positive offset for the relatively low energy storage compared to existing battery systems. An observed improvement in the specific capacity during repetitive cycling was related to the presence of Cu and sulfide sulfur species on the CuFeS 2 particles as revealed from the characterization of retrieved CuFeS 2. Graphical abstract Image 1 Highlights • A mined mineral concentrate of CuFeS 2 is used in a fixed bed flow cell. • Electrochemical reactions in the FBFC were quasi-reversible. • With the mineral concentrate the cell could supply up to 8.5 Wh kg−1 in 400 cycles. • In addition to energy storage, ∼12% Cu was extracted from the mineral concentrate. • Ex-situ analysis revealed the formation of an iron deficient Cu x S phase. [ABSTRACT FROM AUTHOR]

Most copper minerals are found as sulfides, with chalcopyrite being the most abundant. However; this ore is refractory to conventional hydrometallurgical methods, so it has been historically exploited through froth flotation, followed by smelting operations. This implies that the processing involves polluting activities, either by the formation of tailings dams and the emission of large amounts of SO2 into the atmosphere. Given the increasing environmental restrictions, it is necessary to consider new processing strategies, which are compatible with the environment, and, if feasible, combine the reuse of industrial waste. In the present research, the dissolution of pure chalcopyrite was studied considering the use of MnO2 and wastewater with a high chloride content. Fine particles (−20 µm) generated an increase in extraction of copper from the mineral. Besides, it was discovered that working at high temperatures (80 °C); the large concentrations of MnO2 become irrelevant. The biggest copper extractions of this work (71%) were achieved when operating at 80 °C; particle size of −47 + 38 µm, MnO2/CuFeS2 ratio of 5/1, and 1 mol/L of H2SO4.

Due to its high availability, low cost, and outstanding electrochemical capabilities, CuFeS 2 is a viable electrode material for lithium-ion batteries (LIBs). Its actual application is constrained, nonetheless, by substantial capacity fading and polysulfide production during the electrochemical process. To enhance the electrochemical characteristics and the chemical dissolution stability of the electrolyte, we present an optimal solvothermal synthesis of CuFeS 2 with spherical morphology and high phase purify. The subsequent thermal pyrolysis with dopamine hydrochloride forms a uniform coating of N-doped carbon (NC) on the surface of CuFeS 2 spheres. The successful NC coating increases the electronic conductivity of CuFeS 2 and Li+ ion diffusion kinetics, and thus dramatically improves the rate and cycle performances of the constructed half cells and full LIBs. The ideal CuFeS 2 @NC with a 10 wt% NC anode demonstrates a reversible capacity of 878.6 mAh·g-1 at a current density of 0.5 C after 300 cycles, which is 93.4% of the initial capacity, and the coulombic efficiency remains above 98%. The fundamental charge and discharge mechanisms of CuFeS 2 @NC anodes are clarified by in situ electrochemical XRD analysis, and their primary mechanism for storing lithium is the "insertion-conversion" reaction. [ABSTRACT FROM AUTHOR]

Development of thermoelectric materials based on iron-sulfide minerals is reviewed with focusing on n-type doped CuFeS2. It is found that the thermoelectric properties of Zn-doped CuFeS2 strongly depend on the synthesis method, especially on the cooling rate and heat treatment conditions after spark-plasma sintering (SPS). A high power factor exceeding 1 mW/K2m is achieved around room temperature for samples annealed and slowly cooled after SPS. With aiming at reducing thermal conductivity, several methods are applied including the high-pressure torsion technique and nano-structuring by ball milling. These experiments successfully yield reduced thermal conductivity, though experimental conditions needs to be optimized to reduce electrical resistivity simultaneously. [ABSTRACT FROM AUTHOR]

This study focuses on the synthesis and properties of CuFeS 2 chalcogenides, which were prepared using a heat precipitation method. The effect of synthetic temperature on the catalytic activity of CuFeS 2 was also investigated. The study found that CuFeS 2 prepared at 250 °C (CuFeS 2 –250) had higher crystallinity, a higher concentration of Fe2+ on its surface, and a higher catalytic activity in the decolorization of rhodamine B (RhB) using a Fenton-like oxidation process with Na 2 S 2 O 8 (99.0% RhB decolorization efficiency within 7 min). The iron sites of CuFeS 2 were found to be the catalytic active sites through density-functional theory calculations. The study also determined that •SO 4 − and •OH radicals were the reactive species responsible for the decolorization of RhB. In addition, the study demonstrated that CuFeS 2 –250 had the ability to decolorize different dyestuffs (methylene blue, methyl orange, and acridine orange) in environmental water samples (river and seawater). Furthermore, CuFeS 2 –250/Na 2 S 2 O 8 possessed excellent antibacterial activity (>90.4% eradication rate within 120 min) against pathogen (Escherichia coli , Staphylococcus aureus , and methicillin-susceptible S. aureus). In conclusion, this study highlights the enhanced catalytic activity of CuFeS 2 –250 and its potential for industrial applications related to the decomposition of organics from wastewater. Enhanced catalytic of CuFeS 2 -250/Na 2 S 2 O 8 for decolorization and disinfection of organics in wastewater. [Display omitted] • CuFeS 2 was prepared by a heat precipitation method. • The iron site was the catalytic active site. • Decolorization efficiency was 99.0%. • Excellent recycling runs and stability. • Antibacterial activity of 90.4% was found. [ABSTRACT FROM AUTHOR]

Con el objetivo de estudiar el efecto de la activación mecánica sobre la lixiviación de CuFeS2, cuatro muestras de este mineral fueron sometidas a molienda durante 1, 5, 8, y 15 h en un molino Atritor. Los polvos obtenidos fueron caracterizados microestructuralmente y morfológicamente mediante difracción de Rayos-X (DRX) y microscopía electrónica de barrido (MEB), respectivamente. Posteriormente fueron lixiviados en una solución de H2SO4(0,54 M) a temperatura de 298 K. La concentración de Cu+2 en las soluciones fue determinada mediante espectrofotometría de absorción atómica. Los resultados obtenidos indicaron que el aumento del tiempo de molienda provoca un aumento en la recuperación de Cu, alcanzando un valor máximo de 38,2 % para una molienda de 15 h.

This review gives an overview on CuFeS 2 (CFS) compound. These materials belong to transition metal chalcogenides (TMC), which can be obtained in different forms like single crystals, thin films, nanoparticles and Quantum dots (QDs). Starting from growth of CFS crystals by different methods like Bridgman, vapour transport techniques, solid-state reaction, etc., are discussed with their characteristic properties. Justification of increased potential of CFS by doing doping is also revealed in this article. The CFS thinfilms depositions reported in literature by different techniques are discussed. The use of the thin films for fabrication of solar cell as an alternate source of energy is also discussed. The CFS nanoparticles and nanocrystals showed significantly enhanced and modified intrinsic properties with different synthesis methods/conditions are included in this review. The key reports, fabrication strategies, and applications of CFS quantum dots as emerging materials are explained. The main advantages and limitation of CFS as single crystal, thin-films, nanoparticles, and quantum dots are also covered. The CFS materials in above varied forms have enough potential to be used in photovoltaic, photocatalysis, biomedicines, biosensors, and power storage applications. [ABSTRACT FROM AUTHOR]

Poor stability retards the industrialization of perovskite solar cells (PSCs). One of the effective ways to solve this issue is to modify the perovskite surface to improve the efficiency and stability of the PSCs. Herein, we synthesized CuFeS 2 nanocrystals and applied them to modify the perovskite surface. The efficiency of the PSCs with CuFeS 2 modification is improved to 20.17% from 18.64% for the control devices. Some investigations demonstrate that the CuFeS 2 modification passivates the perovskite surface defects and induces better energy band arrangement. Furthermore, the stability of the PSCs with CuFeS 2 modification is improved compared with the devices without CuFeS 2 modification. The efficiency of the PSCs with CuFeS 2 modification maintains 93% of its initial value, whereas that of the devices without CuFeS 2 modification decreases to 61% of the initial value. This work demonstrates that CuFeS 2 is a novel material used as a modification layer to enhance the efficiency and stability of the PSCs.

In order to study the effect of mechanical activation on the sulphuric acid leaching of CuFeS2, four samples were milled using an Atritor mill during 1, 5, 8, and 15 h. The powders were microstructural and morphologically characterized by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The samples were leached using a solution of H2SO4 (0.54 M) at 298 K. The Cu+2 concentration was determined by means of atomic absorption spectrophotometry. The results obtained indicated that the increase in milling time results in increased recovery of Cu. The maximum recovery of Cu was 38.2 % for a milling time of 15 h.

Abstract: CuFeS2 alloys composed of common and non-toxic elements were synthesized by combining mechanical alloying (MA) and spark plasma sintering (SPS). The CuFeS2 compound powders were synthesized directly by MA process, which were then spark plasma sintered to bulk materials. It was found that S content in the bulk samples became deficient depending on the fabrication conditions, and the ZT value improved slightly with decreasing S content. Under the optimized condition, CuFeS2− x (0 ⩽ x⩽ 0.25) samples were prepared to investigate the effect of S deficiency on the thermoelectric properties. The electrical resistivity and thermal conductivity decreased gradually with decreasing S content, resulting in a maximum ZT value of 0.21 at 573K for the sample CuFeS1.80. [Copyright &y& Elsevier]

Abstract: The incorporation of metal impurities M (M=Ti, Fe, or Sn) into CuGaS2 films is investigated experimentally as a function of impurity concentration. Films are synthesized by thermal co-evaporation of the elements onto glass/Mo substrates heated to 400°C–570°C. The compositions of the resulting films are measured by energy-dispersive X-ray spectroscopy and the structures of the present phases are studied by X-ray diffraction. The formation of Cu–M–S ternary phases is observed in a wide range of conditions. Films of Cu–Ga–Ti–S, synthesized at 500°C, show the presence of a cubic modification of CuGaS2 and Cu4TiS4. Alloying of CuGaS2 and tetragonal Cu2SnS3 is observed for substrate temperatures of 450°C. A miscibility gap opens at 500°C and above with separate Sn-rich and Ga-rich phases. Similarly, alloys of CuFeS2 and CuGaS2 are only found in Cu–Ga–Fe–S films synthesized at lower substrate temperature (400°C), whereas at 500°C a miscibility gap opens leading to separate Fe-rich and Ga-rich phases. [Copyright &y& Elsevier]

Abstract: A solventothermal reaction route has been developed to prepare chalcopyrite phase CuFeS2 nanowires with a diameter of about 50nm and a length up to several micrometers at 150–220°C. The phase, morphology, composition and purity of the products have been investigated using X-ray diffraction, field-emission scanning electron microscope, transmission electron microscope and X-ray photoelectron spectra methods, respectively. The 57Fe Mössbauer spectrum exhibits a six-peak hyperfine magnetic spectrum and a like-splitted line non-magnetic peak. Ethylenediamine played an important role in the formation of the ternary sulfides. A mechanism is proposed to explain the chemical reactions. [Copyright &y& Elsevier]

In this manuscript, low-cost chalcopyrite (CuFeS 2) nanostructures as a potential thermoelectric material are explored. Cu x Fe 1- xS 2 (x = 0, 0.1, 0.3 & 0.5) samples were fabricated by simple hydrothermal route. X-ray diffraction pattern reveals the formation of CuFeS 2 along with impurity phases of FeS, FeO, and FeS 2. The presence of these unwanted impurity phases goes on decreasing while the improvement in phase purity of CuFeS 2 was observed with the increase in Cu concentration. This improvement in phase purity leads to enhancement in the Seebeck coefficient from 69 to 92 μV/°C (at 25 °C) by increasing the Cu concentration. Hall measurement reveals the significant enhancement of the electrical conductivity values from 90 to 110 S/cm by increasing the Cu concentration. The enhancement in electrical conductivity was associated with the shifting of Cu/Fe stoichiometry that leads to the generation of more free carriers which leads to a high-power factor value up to 9.31 × 10−5 W/mK2. To support our results, some other supplementary measurements such as Raman spectroscopy and scanning electron microscopy were also performed. • Facile synthesis of CuFeS 2 nanostructure by simple hydrothermal method. • Improving the thermoelectric performance of CuFeS 2 nanostructure by controlling the Cu/Fe stoichiometry. • Seebeck coefficient and electrical conductivity were enhanced with Cu content. • Thermoelectric Power factor was increased up to ∼9.31 × 10−5 W/mK2 for x = 0.5. [ABSTRACT FROM AUTHOR]

In this study, Chalcopyrite (CuFeS2) was prepared by a hydrothermal and co-precipitation method, being represented as H-CuFeS2 and C-CuFeS2, respectively. The prepared CuFeS2 samples were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray spectroscopy mapping (EDS-mapping), powder X-ray diffractometer (XRD), X-ray photoelectron spectrometry (XPS), and Raman microscope. Rhodamine B (RhB, 20 ppm) was used as the target pollutant to evaluate the degradation performance by the prepared CuFeS2 samples. The H-CuFeS2 samples (20 mg) in the presence of Na2S2O8 (4 mM) exhibited excellent degradation efficiency (98.8% within 10 min). Through free radical trapping experiment, the major active species were •SO4− radicals and •OH radicals involved the RhB degradation. Furthermore, •SO4− radicals produced from the prepared samples were evaluated by iodometric titration. In addition, one possible degradation mechanism was proposed. Finally, the prepared H-CuFeS2 samples were used to degrade different dyestuff (rhodamine 6G, methylene blue, and methyl orange) and organic pollutant (bisphenol A) in the different environmental water samples (pond water and seawater) with 10.1% mineral efficiency improvement comparing to traditional Fenton reaction. [ABSTRACT FROM AUTHOR]

• Application of CuFeS 2 chalcogenide as a potential photo-Fenton catalyst. • CuFeS 2 prepared by microwave route presented higher catalytic activity. • High concentration of Fe2+ on the CuFeS 2 surface promoted higher catalytic activity. • CuFeS 2 exhibits remarkable degradation efficiency of tatrazine dye. In this work, CuFeS 2 chalcogenide powders were easily produced by conventional and microwave methods, and for the first time, the influence of synthesis route on their properties and consequent catalytic activity in the photo-Fenton reaction was investigated. X-ray diffraction, N 2 adsorption–desorption isotherms, Fourier-transform infrared spectroscopy, transmission and scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were employed to characterize and point out the main properties and differences among samples. The CuFeS 2 particles were used as catalysts for tartrazine dye degradation by the photo-Fenton reaction under visible irradiation. The results showed that the CuFeS 2 prepared by microwave-assisted method (CuFeS 2 –MW) present higher crystallinity, higher concentration of Fe2+ on its surface and remarkable catalytic activity, reaching 99.1% of tartrazine decolorization and 87.3% of mineralization, at a rate twice as fast as CuFeS 2 prepared by the conventional method. The catalyst showed high catalytic efficiency and stability during the reaction after five recycles. The hydroxyl radical was revealed to be the reactive species responsible for tartrazine degradation. A mechanism was proposed to elucidate how these free radicals are generated from the catalytic decomposition of H 2 O 2 by CuFeS 2 –MW. [ABSTRACT FROM AUTHOR]

• Application of citrate-modified CuFeS 2 material as a potential photo-Fenton catalyst. • Addition of citric acid on the CuFeS 2 synthesis accelerates the reduction of Fe3+ to Fe2+ during the photo-Fenton reaction. • The regeneration of Fe2+ promoted a faster production of OH radicals. • CuFeS 2 exhibited remarkable degradation efficiency of bisphenol A under visible light and near-neutral pH. In this study, for the first time, citric acid was employed as a chelating agent in CuFeS 2 synthesis in order to accelerate the regeneration of Fe2+ during the photo–Fenton reaction, promoting a faster production of OH radicals. The novel CuFeS 2 material showed remarkable catalytic efficiency for bisphenol A (BPA) degradation during the photo–Fenton process under visible light and near–natural pH, with a rate 10 times faster than that of CuFeS 2 prepared without citrate. Furthermore, CuFeS 2 promoted rapid generation of OH radicals and showed efficient H 2 O 2 consumption, sustaining the catalytic efficiency and stability even after 4 consecutive cycles of use. CuFeS 2 was also efficient for BPA degradation from a municipal wastewater treatment plant effluent. BPA by–products were identified and a mechanism for BPA degradation was proposed. After the photo–Fenton process, no Fe3+ species were identified on the catalyst surface by X–ray photoelectron spectroscopy (XPS), indicating that citric acid accelerated the conversion of Fe3+/Fe2+, thus increasing the generation of OH and the process efficiency. [ABSTRACT FROM AUTHOR]

Most copper minerals are found as sulfides, with chalcopyrite being the most abundant. However; this ore is refractory to conventional hydrometallurgical methods, so it has been historically exploited through froth flotation, followed by smelting operations. This implies that the processing involves polluting activities, either by the formation of tailings dams and the emission of large amounts of SO2 into the atmosphere. Given the increasing environmental restrictions, it is necessary to consider new processing strategies, which are compatible with the environment, and, if feasible, combine the reuse of industrial waste. In the present research, the dissolution of pure chalcopyrite was studied considering the use of MnO2 and wastewater with a high chloride content. Fine particles (−20 µm) generated an increase in extraction of copper from the mineral. Besides, it was discovered that working at high temperatures (80 °C); the large concentrations of MnO2 become irrelevant. The biggest copper extractions of this work (71%) were achieved when operating at 80 °C; particle size of −47 + 38 µm, MnO2/CuFeS2 ratio of 5/1, and 1 mol/L of H2SO4. [ABSTRACT FROM AUTHOR]