Pure CuInS2 Research Articles

Strong support effect induced by MXene for the synthesis of metal sulfides nanosheet arrays with sulfur vacancies towards selective CO2-to-CO photoreduction

Selective CO2-to-CO photoreduction is under intensive research and requires photocatalysts with tuned microstructures to accelerate the reaction kinetics. Here, we report CuInS2 nanosheet arrays with sulfur vacancies (VS) grown on the two-dimensional (2D) support of Ti3C2Tx MXene for CO2-to-CO photoreduction. Our results reveal that the use of Ti3C2Tx induces strong support effect, which causes the hierarchical nanosheet arrays growth of CuInS2 and simultaneously leads to charge transfer from CuInS2 to Ti3C2Tx support, resulting in VS formed in CuInS2. The strong support effect based on Ti3C2Tx is proven to be applicable to prepare a series of different metal indium sulfide arrays with VS. CuInS2 nanosheet arrays with VS supported on Ti3C2Tx benefit the photocatalytic selective reduction of CO2 to CO, manifesting a remarkable over 14.8-fold activity enhancement compared with pure CuInS2. The experimental and computational investigations pinpoint that VS of CuInS2 resulting from the support effect of Ti3C2Tx lowers the barrier of the rate-limiting step of *COOH → *OH + *CO, which is the key to the photoactivity enhancement. This work demonstrates MXene support effects and offers an effective approach to regulate the atomic microstructure of metal sulfides toward enhancing photocatalytic performance.

Fast photodetection in eco-friendly wurtzite CuInS2 nanocrystals based photodiode with a planar geometry

This study describes the optoelectronic characteristics of CuInS2 nanocrystals (NCs) in wurtzite (WZ) stoichiometry. Non-toxic CuInS2 NCs are successfully synthesized via simple solvothermal method with no secondary phases, due to proper control of copper, indium and sulfide precursors amount. Pure CuInS2 NCs based planar photodetector geometry provides a strong photo-response upon excitation from 390 nm to 950 nm optical spectra, including responsivity up to 21 AW-1, detectivity of 9.8 × 1011 Jones and response-speed of ∼ Tr/Tf = 2.32 s/4.93 s, at 950 nm wavelength. Moreover, to realize a fast response-time, a simple strategy is presented based on providing one vertical photodetector geometry in the lateral form. We designed a micro-spaced trench (channel length ∼ 40 μm) on FTO/glass substrate using CO2 laser. The device shows a noticeably fast response-time ∼ 60 ms over the whole examined spectral range, concomitant with responsivity and detectivity of 264.9 mAW−1 and 7.9 × 1010 Jones at 950 nm wavelength. The fast response-time could be attributed to the photovoltaic mode and the built-in electrical field at the interface between CuInS2 NCs and electron/hole transport layers. This device architecture may provide a proper route toward simple and low-cost alternative designs for photodetectors.

A staggered type of 0D/2D CuInS2/NiAl-LDH heterojunction with enhanced photocatalytic performance for the degradation of 2,4-Dichlorophenol

0D/2D interface heterostructure of 0D CuInS2 and 2D NiAl-LDH were obtained via strong interfacial contact. Mott-Schottky analysis confirmed both materials were n-type feature. Thus, a staggered n-n heterojunction was formed via the balance of Fermi level. This 0D/2D composite exhibited enchantable activity for photocatalytic degradation 2,4-Dichlorophenol under visible-light illumination, far superior than pure CuInS2 and NiAl-LDH. The improvement of photocatalytic performance mainly attributed to the large BET surface area and interfacial contact, which resulted in more active sites, effective charge separation and transfer. Moreover, the optimal CuInS2/NiAl-LDH composite showed higher photostability for cycle experiments. At the same, the possible photocatalytic reaction process was proposed based on the trapping experiments, ESR technique and band position. This work provided a theory and foundation for designing and preparing of 0D/2D heterostructure system for photocatalytic application.

Facile synthesis of sphere-like structured ZnIn2S4-rGO-CuInS2 ternary heterojunction catalyst for efficient visible-active photocatalytic hydrogen evolution

Photocatalysis is a promising approach for generating hydrogen, an eco-friendly and cost-effective fuel. It is hypothesized that the ternary catalyst ZnIn2S4-rGO-CuInS2, prepared by ultrasonication method, should be effective for optimized photocatalytic hydrogen generation in a Na2S/Na2SO3−water mixture. The as-synthesized catalyst was characterized using various surface analytical and optical techniques. Field-emission scanning electron microscopy and high-resolution transmission electron microscopy analyses revealed that marigold-like structured ZnIn2S4 and layer-structured CuInS2 were dispersed on the reduced graphene oxide sheets. The ternary ZnIn2S4-rGO-CuInS2 system showed enhanced photocatalytic H2 production compared to pure ZnIn2S4, CuInS2, ZnIn2S4-rGO, CuInS2-rGO, and ZnIn2S4-CuInS2 catalysts under visible light illumination. The fabricated ZnIn2S4-rGO-CuInS2 catalyst afforded hydrogen generation of 2531 μmol/g after 5 h. The enhanced performance of the ZnIn2S4-rGO-CuInS2 catalyst originates from the synergetic effect with rGO as the electron transfer medium, and is confirmed by photocurrent density and photoluminescence measurements that indicate reduced recombination between the excited electron and hole pairs, and fast electron transfer in the ternary composite. The excellent performance of the ZnIn2S4-rGO-CuInS2 catalyst for up to three consecutive cycles was demonstrated in cyclic stability tests under visible-light illumination.

Impact of non-stoichiometry in the thermoelectric performance of polyol method prepared Cu1+xIn1−xS2 (x = −0.3, −0.2, −0.1, 0, 0.1, 0.2) nanowires

A significantly enhanced thermoelectric power factor at 320 K in a facile polyol method prepared non-stoichiometric Cu1+xIn1−xS2 (x = −0.3, −0.2, −0.1, 0, 0.1, 0.2) nanowires with traces of Cu2S has been demonstrated here. Rietveld refinement of powder XRD and Raman analysis confirm these. Field effect scanning electron microscopy (FESEM) study shows micron size CuInS2 spherical particles made up from 8.8 nm diameter with about 35 nm length nanowires. The dramatic increase in electrical conductivity and hence thermoelectric performance with increasing x is attributed to the formation of defects, Cu2S, and increase in carrier concentrations. The power factor reaches a high of 0.8 μW m−1 K−2 at 320 K and an electrical conductivity of 2800 S/m, which is about 35 and 250 times higher, respectively, than that of pure CuInS2 and hot-pressed Bi2S3 nanorods respectively at this temperature. These results expect high-power factor improvement for power production in the future.

A novel low-temperature growth of uniform CuInS2 thin films and their application in selenization/sulfurization-free CuInS2 solar cells

In terms of manufacturability, there is a high tendency to deposit light-absorbing CuInS2 films by solution processing methods like ink-based depositions. In particular, for nanoparticle inks, the synthesis of highly dispersed and stable inks, with uniformity in the deposition process, is a serious challenge. Here, we demonstrate a novel two-step low-temperature CuInS2 film deposition method in which the In2S3 is deposited first. It then partially is converted into CuInS2 through the infiltration of Cu+ ions in the In2S3 layer in a dip-coating process. The resulting films are highly uniform, with diffraction peaks indicating the formation of pure CuInS2 phase. The proper stoichiometry of CuInS2 layers is confirmed by the optical absorption spectrum, energy–dispersive x-ray spectroscopy, and X-ray photoelectron spectroscopy analysis. Our Cd-free devices are structured by FTO/TiO2/In2S3/CIS/carbon, in which the residual In2S3 film acts as a buffer layer. The results demonstrate that the planar superstrate CuInS2 solar cell with the optimized absorbing layer composition has a power conversion efficiency of 2.11 %, which is the highest reported efficiency for a low-temperature solution-based selenization/sulfurization-free CuInS2 device structures prepared by ion-exchange method.

Ethanol sensing with pure and boric acid doped eectrospun CuInS2 nanofibers in the presence of relative humidity

The influence of boric acid doping on ethanol vapor sensing performance of electrospun copper indium disulfide (CuInS2) nanofibers in the presence of various levels of relative humidity was examined for the first time. Pure and boric doped CuInS2 nanofibers are prepared through electrospinning method and characterized by X-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy and Thermogravimetric analysis techniques. It was found that not only the ethanol sensing performance but also base line current of the CuInS2 nanofiber based sensors are greatly influenced by the boric acid doping level. Maximum sensitivity was obtained with pure CuInS2 under humid conditions. Kinetic studies indicated that ethanol vapor adsorption kinetics strongly depend on level of the relative humidity and the ethanol concentration.

A novel CuInS2/m-BiVO4 p-n heterojunction photocatalyst with enhanced visible-light photocatalytic activity

Novel CuInS2/m-BiVO4 composites with different mass ratios (CuInS2 to m-BiVO4 = 1:3, 1:1, and 3:1) were synthesized and their potential visible-light photocatalytic applications for photodegradation of some organic dyes (methylene blue, rhodamine B, and methyl orange) and inactivation of bacteria (Pseudomonas aeruginosa) were investigated. CuInS2/m-BiVO4 with a mass ratio of 1:3 exhibited better photocatalytic degradation of methylene blue and antibacterial activity than those of either pure CuInS2 or m-BiVO4. Moreover, this composite photocatalyst showed different photocatalytic selectivity in terms of the organic dye degradation. Salicylic acid was also used to test the photocatalytic activity of this composite to clarify the dye sensitization effect. The photoelectrochemical (PEC) properties of the CuInS2/m-BiVO4 photoelectrode, evaluated by linear sweep voltammetry (LSV) measurement, revealed that the composite photoelectrode exhibited higher current density and onset potential in comparison with the m-BiVO4 photoelectrode. In addition, the electrochemical impedance spectroscopy (EIS) measurement also proved a faster rate of charge transfer at the electrode/electrolyte interface. The enhancement of photocatalytic and PEC activities of the CuInS2/m-BiVO4 composite was revealed not only that the CuInS2/m-BiVO4 composite extended light absorption in the visible light region, but also that the formation of a p-n heterojunction could promote photogenerated charges as well as facilitate effective charge separation and transportation between the CuInS2 and m-BiVO4 contact interface.

CuInS2/Sb2S3 heterostructure modified with noble metal co-catalyst for efficient photoelectrochemical water splitting

In order to improve the water splitting efficiency of CuInS2 in a photoelectrochemical (PEC) cell, the novel CuInS2/Sb2S3 heterostructure photocathodes modified with Pt noble metal co-catalyst were prepared on the ITO substrate by the hydrothermal and electrochemical deposition method for the first time. The mechanism of the synthesis reaction for the CuInS2/Sb2S3 and CuInS2/Sb2S3/Pt were investigated. With the photoelectrochemical measurements, the photocurrent density of CuInS2/Sb2S3/Pt photoelectrode (−2.48 mA/cm2 at −0.6 V vs. RHE) is about 3.13 times relatively higher than that of the corresponding the pure CuInS2 photoelectrode (−0.79 mA/cm2 at −0.6 V vs. RHE). The excellent PEC behaviors profit from the modification by Sb2S3 that forms the heterostructure which broadens the response of visible light and increases the separation and transfer of photo-generated carriers. Moreover, after introducing Pt co-catalyst onto the surface of CuInS2/Sb2S3 photoelectrode, photo-generated electrons can be captured quickly which further effectively promotes the separation of photo-generated carriers and greatly improve the PEC performance. This work manifests that the structure of CuInS2/Sb2S3/Pt photocathodes has a guiding suggestion to provide a promising approach to designing a highly stabilized efficient device for photoelectrochemical water splitting.

Construction of CuInS2@ZIF-8 nanocomposites with enhanced photocatalytic activity and durability

Inspired by the unique structure and wide applications of zeolitic imidazolate frameworks-8 (ZIF-8) and CuInS2 (CIS), considerable attention has focused on the combination of both materials. We herein report a facial method for the homogeneous decoration of ZIF-8 onto the surfaces of CuInS2 (CIS) nanoparticles coordinated by polyvinyl pyrrolidone (PVP) in methanol. It has been shown that the coordination of PVP plays a key role in inducing the nucleation of ZIF-8 on the surface of CIS nanoparticles because of the pyrrolidone rings (C = O) in PVP offering an improved affinity between CIS and Zn ions. Performing as a catalyst, the CIS@ZIF-8 nanocomposites not only exhibit high photocatalytic activity for the degradation of organic dye under UV light irradiation, but also largely maintain their catalytic efficiency after being recycled for five times compared with that of pure CIS nanoparticles.

Novel visible-light-driven direct Z-scheme CdS/CuInS2 nanoplates for excellent photocatalytic degradation performance and highly-efficient Cr(VI) reduction

A series of visible-light-driven direct Z-scheme CdS/CuInS2 nanoplates were fabricated by a facile one-step hydrothermal method, and the molar ratio of CdS to CuInS2 was optimized. The highest visible-light photocatalytic degradation activity of Z-scheme (1:0.03) CdS/CuInS2 heterojunction is about 4 times than that of pure CuInS2, which is due to the narrowest band gap, the largest BET surface area, the most efficient charge separation and transfer, and the synergistic effect between CdS and CuInS2. Meanwhile, Z-scheme (1:0.03) CdS/CuInS2 heterojunction also exhibits excellent photocatalytic reduction activity with almost 100% of aqueous Cr(VI) reduction efficiency in absence of hole scavengers after 60 min. The special significance is that Z-scheme (1:0.03)CdS/CuInS2 heterojunction shows excellent stability in five degradation cycles, and can effectively treat real pharmaceutical wastewater with 76.5% COD removal efficiency with aid of H2O2 in 13 h, indicating that Z-scheme CdS/CuInS2 has a promising prospect in real pharmaceutical wastewater treatment.

Deep-red emitting zinc and aluminium co-doped copper indium sulfide quantum dots for luminescent solar concentrators

Pure CuInS2 quantum dots (CIS QDs) exhibited poor photoluminescent (PL) performance due to more dangling bonds on their surface and thus needed a shell to form core@shell structured QDs. However, conventional shells had a higher band gap than CIS QDs so that the core@shell structured QDs showed a blue-shifted PL peak below 700 nm and narrower light absorption range. Herein, Zn and Al co-doped CIS QDs were synthesized by a facile cation exchanged method which can significantly improve the PL property emitting at ∼740 nm compared to pure CIS QDs. The enhancement of the PL property was probably attributed to ZnCu and AlCu defects in the CIS QDs which could cause electron-hole radiative recombination via defect levels, reduce the number of dangling bonds and thus minimize the nonradiative recombination through surface electron trapping. Furthermore, the PL intensity was controlled by doping time and reached the maximum at 30 min. The obtained deep-red emitting CIS QDs were employed to fabricate semi-transparent luminescent solar concentrators (LSCs) which exhibited an excellent optical efficiency of 6.97%. The success in using such Zn and Al co-doped CIS QDs could pave the way to realize high efficiency and environment-friendly LSCs for building integrated photovoltaics.

2D/2D Z-scheme heterojunction of CuInS2/g-C3N4 for enhanced visible-light-driven photocatalytic activity towards the degradation of tetracycline

Photocatalysis is one of the most promising technologies owing to its great potential to relieve energy and environmental issues. Constructing Z-scheme heterojunction photocatalyst with strong redox ability to make for enhanced light absorption and efficient charge separation is extremely attractive but still underdeveloped. Herein, Z-scheme heterojunction of CuInS2/g-C3N4 with a “sheet-on-sheet” hierarchical structure showing enhanced photocatalytic performance for the tetracycline (TC) degradation under visible-light irradiation has been developed. This 2D/2D hierarchical structure of CuInS2/g-C3N4 composite not only enlarges the contact region in the heterojunction interface but also provides more active reaction sites, as demonstrated by the TEM and BET analyses. Particularly, 50 wt% CuInS2/g-C3N4 heterojunction shows the highest photocatalytic activity (20 mg/L; 83.7% degradation within 60 min), which the apparent rate constant is 15 and 11 times higher than that of pure g-C3N4 and CuInS2 nanosheets, respectively. The remarkably enhanced photocatalytic activity mainly derives from the synergistic effect between CuInS2 and g-C3N4, thereby promoting the charge separation during the photocatalytic reaction. This work is expected to provide a design idea to construct multifunctional 2D/2D nanocomposites for photocatalytic applications.

Facile and Robust Solvothermal Synthesis of Nanocrystalline CuInS₂ Thin Films.

This work demonstrates that the solvothermal synthesis of nanocrystalline CuInS2 thin films using the amino acid l-cysteine as sulfur source is facile and robust against variation of reaction time and temperature. Synthesis was carried out in a reaction time range of 3–48 h (at 150 °C) and a reaction temperature range of 100–190 °C (for 18 h). It was found that at least a time of 6 h and a temperature of 140 °C is needed to produce pure nanocrystalline CuInS2 thin films as proven by X-ray and electron diffraction, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Using UV-vis spectroscopy, a good absorption behavior as well as direct band gaps between 1.46 and 1.55 eV have been determined for all grown films. Only for a reaction time of 3 h and temperatures below 140 °C CuInS2 is not formed. This is attributed to the formation of metal ion complexes with l-cysteine and the overall slow assembly of CuInS2. This study reveals that the reaction parameters can be chosen relatively free; the reaction is completely nontoxic and precursors and solvents are rather cheap, which makes this synthesis route interesting for industrial up scaling.

Ultrathin Hexagonal SnS2 Nanosheets Coupled with Tetragonal CuInS2 Nanosheets as 2D/2D Heterojunction Photocatalysts Toward High Visible-Light Photocatalytic Activity and Stability

A kind of 2D/2D heterojunction photocatalysts was constructed by a facile in situ hydrothermal method that a tetragonal CuInS2 nanosheets was horizontal loaded in ultrathin hexagonal SnS2 nanosheets. Contrasted to pure CuInS2 and SnS2 nanosheets, the CuInS2/SnS2 nano-heterojunctions revealed a noteworthy improvement photocatalytic activity under visible light irradiation for the degradation of organic dyes, which should be attributed to the narrowest band gap and the efficient charge separation and transfer improving the contact region in heterojunction interface. Especially, with 0.5 wt% addition of CuInS2, the heterojunction nanosheets shows a supreme visible-light photocatalytic activity and a superb degradation efficiency which reached 99% in 60 min with the solution of methyl orange. Moreover, CuInS2/SnS2 nano-heterojunctions deliver excellent reusability in five degradation–regeneration cycles. The results indicated that CuInS2/SnS2 has a promising prospect in organic pollutant treatment due to high efficiency and excellent stability.

Structure and band gap tunable CuInS2 nanocrystal synthesized by hot-injection method with altering the dose of oleylamine

By hot-injection method with altering the dose of oleylamine (OAm) in a reaction system, CuInS2 (CIS) nanocrystal with tunable structure and band gap is synthesized. Through various measurements, including X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), it is demonstrated experimentally that when the dose of OAm is relatively high (2.0 and 2.5ml in this work), the combination phase of pseudo-chalcopyrite/wurtzite are obtained with a surprising existence of nanotwins. Besides, the molar fraction of wurtzite is larger in the sample using 2.5ml OAm in the reaction system. However, when the dose of OAm becomes low, (0, 1.0 and 1.5ml), pure zinc-blende CIS pyramidal quantum dots (QDs) can be prepared. This indicates that oleylamine promotes the formation of wurtzite structure. In addition, the band gap is larger with increasing of OAm, following the quantum refinement effects. This work serves as a facile method of synthesizing CIS nanocrystal with tunable structure and band gap, which will be possibly applied in the fabrication of their optoelectronic devices.

Enhanced photocatalytic activity of ternary CuInS2 nanocrystals synthesized from the combination of a binary Cu(I)S precursor and InCl3

Ternary copper indium sulfide (CIS) nanocrystals (NCs) have been synthesized by mixing of binary precursor [CuI(bdpa)2][CuICl2] (1) and/or [CuI(mdpa)2][CuICl2] (2) (where, mdpa and bdpa represent methyl and benzyl ester of 3,5-dimethyl pyrazole-1-dithioic acid, respectively) with InCl3 in a low-temperature solvothermal process. The +1 oxidation state of copper and the atomic ratio Cu to S (1:2) is atomically maintained in the pyrazole-based Cu(I)–S precursor to synthesize phase pure CuInS2. Coordinating solvents like ethylene diamine (EN) and ethylene glycol (EG) have been used in the synthesis without any surfactants. No use of external surfactants in the synthesis of CIS nanoparticles reveals that precursor acts as stabilizing agent. The synthesized nanocrystals were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray spectroscopy (EDX) studies. The optical property of the nanocrystals shows a pronounced quantum confinement effect in the particles with band gap energy ca. 1.5 eV. The formation mechanism of ternary CIS has been proposed. The pore size distributions of the particles show the average pore diameters 13.1 nm from 1 and 5.3 nm from 2. The calculated values of the specific surface area are 8.123 and 9.577 m2/g for 1 and 2, respectively. The excellent photocatalytic degradation of rose bengal (RB) and rhodamine B (RhB) was demonstrated by the porous CIS nanocrystals.

Cyclic microwave radiation synthesis, photoconductivity, and optical properties of CuInS2 hollow sub-microspheres

CuInS2 powder was synthesized by a cyclic microwave irradiation method using l-cysteine as a sulfur source. The effect of microwave power (180–600 W) on the purity, morphology, and particle size of the synthesized powders was investigated. X-ray diffraction (XRD) analysis showed that the synthesized powders were pure CuInS2 with a tetragonal structure. Transmission electron microscopy (TEM) analysis revealed that the CuInS2 powder synthesized at 180 W composed of solid microspheres with a diameter of about 250 nm. Increasing the microwave power to 300 W and 450 W transformed some of the sub-microspheres into hollow sub-microspheres. At 600 W, all of the CuInS2 sub-microspheres were hollow. Based on time-dependent experiment, formation mechanisms of the CuInS2 solid and hollow sub-microspheres were discussed. The photoconductivity of the CuInS2 hollow sub-microspheres was greater than that of the CuInS2 solid sub-microspheres, suggesting that the CuInS2 hollow sub-microspheres were favorable to increase current carrier concentration and to improve electron transport. UV–vis diffuse reflectance spectrum (UV–vis DRS) of the CuInS2 hollow sub-microspheres showed strong absorption intensity with a direct band gap energy of 1.48 eV, which is potentially useful in solar-light driven applications.

Unique surface structure of nano-sized CuInS2 anchored on rGO thin film and its superior photocatalytic activity in real wastewater treatment

Nano-sized CuInS2 was evenly anchored on the thin film of reduced graphene oxide (rGO/CuInS2) by a simple one-step solvothermal method. The photocatalytic activity of rGO/CuInS2 was much higher than that of pure CuInS2, and was highly dependant on rGO amount with results revealing an optimal rGO content of 1 wt%. The 1% rGO/CuInS2 composite demonstrated the highest visible-light photocatalytic activity with almost 90% 2-nitrophenol removal, which was almost two times of pure CuInS2. The enhanced photocatalytic activity of rGO/CuInS2 is ascribed to that the ultrathin film structure of rGO endows rGO/CuInS2 composites with a large density of exposed active sites to reactants, short transport distances of photogenerated charges and the efficient separation of charge carriers. Of special significance is that 1% rGO/CuInS2 composite can effectively treat real pharmaceutical wastewater with 86.5% chemical oxygen demand (COD) removal efficiency in 11 h. Moreover, there was no obvious decrease in the photocatalytic activity of rGO/CuInS2 composites after four photocatalytic cycles. The high COD removal efficiency of pharmaceutical wastewater and reusability indicate the great potential of rGO/CuInS2 in environmental purification of organic pollutants.

Observation of enhanced photocurrent response in M–CuInS2(M = Au, Ag) heteronanostructures: phase selective synthesis and application

We demonstrate the phase selective synthesis of M–CuInS2(M = Au and Ag) heteronanostructures and their enhanced photocurrent activity compared to that of pure CuInS2.