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In the past decade, significant development has been made in the fabrication of new electrocatalysts for high-performance energy conversion and storage. Among various approaches, metal sulfides such as CuS and MnS have shown great potential as effective non precious electrocatalysts in tailoring the atomic and electronic structures of catalytically active materials toward enhanced electrocatalytic activity. We demonstrate here the use of CuS and MnS composites as cost-effective counter electrode material in Quantum-dot sensitized solar cells (QDSSCs). The introduced new composite material has been synthesized using simple and facile process of hydrothermal methods. The surface morphology, composition and composite structure have been confirmed by high-resolution scanning electron microscopy (HR-SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The composite CuS/MnS deposited on FTO substrate-based QDSSCs achieves superior power conversion efficiency (PCE) of 4.38% than those of bare CuS (3.71%) and MnS (2.02%) counter electrodes. The electrochemical analysis showed that the CuS/MnS/FTO composite shows a smaller charger-transfer resistance between the counter electrode/polysulfide electrolyte than the CuS and MnS electrodes, respectively.

Nanocomposite electrodes receive much attention because of their excellent energy storage nature. Electrodes for supercapacitors have come a major source of interest. In this pursuit, the current work elucidates binder-free coral reefs resembling ZnO/CoS2 nanoarchitectures synthesized on the surface of Ni foams employing the cost-effective hydrothermal route. The Zno/CoS2 nanocomposite demonstrated excellent battery-type behavior, which can be employed for supercapcitor application. Various analyses were carried out in the current study, such as X-ray diffraction and high-resolution scanning electron microscopy, which allowed defining the crystalline nature and morphology of surface with ZnO/CoS2 nanoarchitectures. Electrochemical measures such as cyclic voltammetry, galvanostatic charge discharge, and potentiostatic impedance spectroscopy confirmed the battery-type behavior of the material. The synthesized precursors of binder-free ZnO/CoS2 nanostructures depicted an excellent specific capacity of 400.25 C·g−1 at 1 A·g−1, with a predominant cycling capacity of 88. 2% and retention holding of 68% at 10 A·g−1 and 2 A·g−1, even after 4000 cycles, representing an improvement compared to the pristine ZnO and CoS2 electroactive materials. Therefore, the electrochemical and morphological analyses suggest the excellent behavior of the ZnO/CoS2 nanoarchitectures, making them promising for supercapacitors.

Cone-shaped CuS@MnS nanostructures were grown on Ni foam with robust adhesion using a one-step hydrothermal method and efficiently served as binder-free battery-type material for high-performance supercapacitors. The synergic effects of the unique nanostructure and great adhesion is advantageous for enhancing the surface area on the Ni foam substrate, increasing the storage and charge accumulation, increasing the electrochemical activity between CuS and MnS, and accelerating electron and electrolyte ion transfer. As a result, as a battery-type material, the CuS@MnS/NF composite electrode exhibited excellent electrochemical performance, including high specific capacity (89.77 mA h g−1 at a current density of 1 A g−1), good cycling stability (95.9% capacity retention after 3000 cycles), and outstanding rate capability compared to that of CuS/NF (45.73 mA h g−1) and MnS/NF (3.8 mA h g−1). This study sheds new light on the composites, and demonstrates that the CuS@MnS/NF electrode is an ideal material for electrochemical energy storage.

Cauliflower-like ZnWO4@WS2 composite was synthesized on the surface of nickel foam using a low cost and facile two-step hydrothermal method and evaluated as an electrode material for high-performance supercapacitors. The electrochemical properties of the ZnWO4@WS2 electrode were examined by cyclic voltammetry, galvanostatic charge-discharge tests, and electrochemical impedance spectroscopy. The ZnWO4@WS2 redox-active material delivered a high specific capacitance of 1280.7 F g−1 at a current density of 3 A g−1 in a three-electrode configuration. In addition, the ZnWO4@WS2 electrode material showed acceptable long cycle-life stability with 88.41% specific capacitance retention after 3000 cycles at a current density of 6 A g−1, which is superior to that of the ZnWO4 electrode. The higher electrochemical properties were attributed to the synergistic effect and high surface area. The superior electrochemical performance of cauliflower-like ZnWO4@WS2 composite materials highlights their potential to meet the requirements of practical electrochemical energy storage applications.

Binder-free nanorice-like featured CuS@WS2 structures have been synthesized using a simple and cost-effective chemical bath deposition approach and their application as electroactive material for high-performance supercapacitors. The surface properties of morphology, structure and composition of the as-prepared electrodes are examined using the scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The nanorice-like featured CuS@WS2 electrode exhibits nanorice-like structures, which provides the abundant active sites for redox reactions and facilitates the electrolyte diffusion. The electrochemical performance of the supercapacitor electrodes was examined by cyclic voltammetry and galvanostatic charge–discharge studies. From the electrochemical tests, the CuS@WS2 electrode exhibits a higher specific capacitance (Cs) of 887.15 F g−1 at a current density of 3.75 A g−1 with greater energy density and excellent rate capability compared to bare CuS (588.0 F g−1) and WS2 (19.40 F g−1) electrodes. Overall, these results demonstrate that the as-synthesized CuS@WS2 could be a promising material for next-generation high-performance electrochemical energy storage applications.

Copper sulfide is an important multifunctional semiconductor that has attracted considerable attention owing to its outstanding properties and multiple applications, such as energy storage and electrochemical energy conversion. This paper describes a cost-effective and simple low-temperature solution approach to the preparation of copper sulfide for supercapacitors (SCs) and quantum-dot sensitized solar cells (QDSSCs). X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy confirmed that the nickel foam with a coriander leaf like nanostructure had been coated successfully with copper sulfide. As an electrode material for SCs, the CC-3 h showed excellent specific capacitance (5029.28 at 4 A g−1), energy density (169.73 W h kg−1), and superior cycling durability with 107% retention after 2000 cycles. Interestingly, the QDSSCs equipped with CC-2 h and CC-3 h counter electrodes (CEs) exhibited a maximum power conversion efficiency of 2.52% and 3.48%, respectively. The improved performance of the CC-3 h electrode was attributed mainly to the large surface area (which could contribute sufficient electroactive species), good conductivity, and high electrocatalytic activity. Overall, this work delivers novel insights into the use of copper sulfide and offers an important guidelines for the fabrication of next level energy storage and conversion devices.

Unique ZnMn2O4@ZnFe2O4 microspheres were fabricated on Ni foam using a facile and cost-effective hydrothermal method for high-performance supercapacitor applications. The resulting ZnMn2O4@ZnFe2O4 electrode was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electrochemical techniques. The ZnMn2O4@ZnFe2O4 electrode exhibited a microsphere-like morphology with a mean size of ∼50–115 nm. The electrochemical performance of the ZnMn2O4@ZnFe2O4 electrode was investigated and the results showed that the ZnMn2O4@ZnFe2O4 electrode exhibits a high specific capacitance of 1024.66 F g−1 at 10 mA cm−2, low internal resistance, and remarkable cycling stability with 95.8% capacitance retention after 3000 charge–discharge cycles, which was superior to those of the ZnMn2O4 and ZnFe2O4 electrodes. Such enhanced electrochemical performance and the facile synthetic method of ZnMn2O4@ZnFe2O4 electrode materials offer great promise in next generation supercapacitor applications.

This paper reports the facile synthesis of a novel architectural of NiS/PEDOT:PSS with DEG, where the complementary features of the three components (well-defined NiS black pepper like nanoparticles on nickel foam, an ultrathin layers of poly (3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS), and diethylene glycol (DEG)) are deposited sequentially to a single entity to fabricate a high-performance electrode for supercapacitor applications. Owing to the high electrical conductivity of the well-defined NiS nanoparticles, in which the conductivity, and good chemical and electrochemical stability is enhanced further by the PEDOT:PSS and DEG thin layers, the as-fabricated NiS/PEDOT:PSS with a DEG chrysanthemum petal-like nanostructure exhibits good rate capability, excellent cycling stability, and high specific capacitance. The PEDOT:PSS with DEG offers extra conductive paths for each layer on NiS, yielding a lower internal resistance and charge-transfer resistance than that of the NiS/PEDOT:PSS without DEG. As a result, the NiS/PEDOT:PSS with the DEG electrode shows a tremendous pseudocapacitance of 750.64 F g −1 at 1.11 A g −1 , along with a high energy density of 24.52 Wh kg −1 at a power density of 138.88 W kg −1 and good cycling stability, suggesting that it is a promising candidate for energy storage. The unique performance of NiS/PEDOT:PSS with a DEG benefits from its unique chrysanthemum petal-like nanostructure, which could offer faster ion and electron transfer ability, greater reaction surface area and good structural stability.

This paper proposes a novel and facile strategy to synthesize hierarchical nanostructured NiCo2S4via a simple hydrothermal reaction combined with a post anion-exchange reaction that was used directly as an electrode in supercapacitor and quantum-dot sensitized solar cells. By applying the appropriate material concentration, deposition temperature, and time, the NiCo2S4 was densely deposited over the entire surface of the Ni foam with good adhesion. The NiCo2S4 electrode exhibited outstanding electrochemical performance in both the applications with a high specific capacitance of 1612.95 F g−1, energy density of 56 W h kg−1 at 5 A g−1, good cycling stability, power conversion efficiency of 3.94%, and Jsc of 12.27 mA cm−2. The NiCo2S4 electrode exhibited almost double the output values compared to NiCo2O4 (693.6 F g−1 at 6.66 A g−1 and efficiency of 1.81%) and NiCo2Se (1401.4 F g−1 at 10 A g−1 and efficiency of 3.86%), resulting from the excellent electrochemical performance of the NiCo2S4. Overall the excellent performance of the fabricated electrode was attributed mainly to the highly electrocatalytic activity, large surface area and decent conductivity of the hierarchical nanostructures of the NiCo2S4. This study shows that the NiCo2S4 nanostructures can be applied not only in high energy density fields, but also in high power density and energy harvesting applications.

A novel approach for the synthesis of CoxNiyS nanoparticles on fluorine-doped tin oxide (FTO) and nickel-foam (Ni-foam) substrates for methanol oxidation in alkaline media is described. The introduced electrocatalyst was synthesized using different concentrations of cobalt (Co) and nickel (Ni) via a simple and effective process; the electrochemical properties were assessed by cyclic voltammetry. The Co90%Ni10% catalyst showed a current density of −0.576 and −0.801 mA on FTO and Ni-foam, respectively, which is the best for the oxygen reduction reaction. The observed electrocatalytic activity proves that the Ni content plays a crucial role in the enhanced current density. Co90%Ni10% also showed superior stability; 78.75% of the electroactive area remained compared to 67.31% in the case of Co0%Ni100% on Ni-foam. Moreover, the optimized catalyst was used as a counter electrode (CE) in quantum-dot sensitized solar cells and showed greater catalytic activity in a polysulfide redox electrolyte than CuS and Pt based CEs. As a result, under 1 sun illumination, Co90%Ni10% exhibited a power conversion efficiency of up to 2.89%, which was much higher than that of the Pt (1.32%) and CuS (2.03%) CEs. The power conversion efficiency of Co90%Ni10% was enhanced by the surface morphology, roughness factor, and current density, which permit prompt electron transport and lower the charge transfer resistance rate for the polysulfide redox electrolyte.

To make quantum-dot sensitized solar cells (QDSSCs) competitive, photovoltaic parameters such as the power conversion efficiency (PCE) and fill factor (FF) must become comparable to those of other emerging solar cell technologies. In the present study, a novel strategy has been successfully developed for a highly efficient surface-modified platinum (Pt) counter electrode (CE) with high catalytic activity and long-term stability in a polysulfide redox electrolyte. The reinforcement of the Pt surface was performed using a thin passivating layer of CuS, NiS, or CoS by simple chemical bath deposition techniques. This method was a more efficient method for reducing the electron recombination in QDSSCs. The optimized Pt/CuS CE shows a very low charge transfer resistance of 37.01 Ω, which is an order of magnitude lower than those of bare Pt (86.32 Ω), Pt/NiS (53.83 Ω), and Pt/CoS (73.51 Ω) CEs. Therefore, the Pt/CuS CEs show much greater catalytic activity in the polysulfide redox electrolyte than Pt, Pt/NiS and Pt/CoS CEs. As a result, under one-sun illumination (AM 1.5G, 100 mW cm(-2)), the Pt/CuS CE exhibits a PCE of 4.32%, which is higher than the values of 1.77%, 2.95%, and 3.25% obtained with bare Pt, Pt/CoS, and Pt/NiS CEs, respectively. The performance of the Pt/CuS CE was enhanced by the improved current density, Cu vacancies with increased S composition, and surface morphology, which enable rapid electron transport and lower the electron recombination rate for the polysulfide electrolyte redox couple. Electrochemical impedance spectroscopy and Tafel polarization revealed that the hybrid CEs reduce interfacial recombination and exhibit better electrochemical and photovoltaic performance compared with a bare Pt CE. The Pt/CuS CE also shows superior stability in the polysulfide electrolyte in a working state for over 10 h, resulting in a long-term electrode stability than Pt CE.

We report new types of TiO2@CdS and TiO2@ZnS binary structures fabricated by decorating TiO2 surfaces with CdS or ZnS nanoparticles. The material characterization shows that the presence of CdS on the TiO2 surface results in a red-shift of the material band edge in the visible region compared to pure TiO2. A further enhancement of visible light was achieved by N719 dye loading on TiO2@CdS. The binary structure electrode with TiO2@ZnS-4 extended the absorption edge to the visible region and was used as an efficient photo-anode in dye-sensitized solar cells (DSSCs). The experimental results indicate that replacing Ti2+ with Zn2+ ions on the surface greatly increases the surface stability compared to TiO2. Furthermore, Zn and S impurities have a drastic impact on the host material and can create new energy states that can delay the exciton recombination and allow charge separation. The DSSCs based on the TiO2@ZnS-4 photo-anode achieved a power conversion efficiency (PCE) of 4.91% under one sun light illumination, which is higher than those of bare TiO2 (2.84%) and TiO2@CdS-4 (1.44%). This work demonstrates a promising way to design efficient photo-anodes for use in DSSCs that can achieve a high PCE with a lower recombination rate during electron transportation.

To make quantum dot-sensitized solar cells (QDSSCs) more attractive, it is necessary to achieve higher power conversion efficiency. A novel Mn-doped ZnS has been successfully fabricated on CdS/CdSe quantum dots (QDs) by simple successive ion layer adsorption and reaction (SILAR) technique. The Mn-doped ZnS is used as a passivation layer in the QDSSCs. The performance of the QDSSCs was examined in detail using sulfide/polysulfide electrolyte with a Pt or copper sulfide (CuS) counter electrode. Here we demonstrated, the fabricated Mn-doped ZnS QDs shows an improved Voc (0.65 V) compared to bare ZnS QDs (0.60 V). The QDSSC based on a photoanode with Mn-doped ZnS (10 wt% of Zn) shows higher Jsc (15.32 mA cm−2) and power conversion efficiency (4.18%) compared to the bare ZnS photoanode (2.90%) under AM 1.5 G one sun illumination. We explore the reasons for this enhancement and demonstrated that it is caused by improved passivation of the ZnS surface by Mn ions, leading to a lower recombination of photo-injected electrons with the electrolyte. The effect of Cu ions in ZnS has been investigated by UV–Vis spectra and current density–voltage analysis.

Polyvinyl pyrrolidone (PVP) and iron pyrite (FeS2) films are good to enhance the electrochromic devices as they serve as a surface stabilizer, nanoparticle dispersant, growth modifier, and reducing agent. The synthesis of FeS2 with PVP provides an easy pathway for electrolyte penetration which can improve the electrochemical performances in supercapacitor applications. In this work, we report a facile single-step chemical bath deposition technique to synthesis the FeS2/PVP on Ni foam for the first time. The broad bean-like nanostructure of FeS2 is fully covered with PVP nanoparticles and formed like a coagulation nanostructure on Ni foam. The FeS2/PVP/NF composite was evaluated as an efficient electrode for supercapacitor in 3 M KOH solution, exhibited a greater specific capacitance of 526.08 F g−1 at 1 A g−1, high cyclic stability, remain 91.2% of the initial capacitance after 3000 cycles and high rate capability which is higher compared to bare FeS2/NF electrode (434.9 F g−1 at 1 A g−1 and cyclic stability of 76.7%). The remarkable electrochemical performance of FeS2/PVP/NF composite is attributed to its enhanced electroactive sites, higher surface area, fast electron, and ion transport pathway and most importantly for its facile electrolyte infiltration into the FeS2/PVP/NF.

The dense cloud like tiny bundles consisting of CuS nanoparticles were prepared successfully by a simple facile one-step chemical bath deposition method. The CuS electrodes at three different time periods such as 5, 10 and 20 h were prepared and their crystallographic phase, structural, morphological and the composition of the as-prepared electrodes are studied in detail. The CuS-10 h electrode possessed the dense cloud like structured nanoparticles on the surface of the Ni foam created pathways in a more efficient manner that allows the swift mobility of electrons/ions. Moreover, the electrochemical behavior and performance of the electrodes are carried out in a 3 M KOH electrolyte in the three-electrode system. The cyclic voltammetry and galvanostatic charge/discharge results confirm that all the fabricated CuS electrodes exhibit the battery-type behavior. As a battery-type material, the binder-free CuS-10 h electrode exhibits the enhanced specific capacity of 164.053 m Ah g−1 at 1 A g−1, higher rate capability of 82.54% and good cycling stability of 97.12% after 4000 cycles, respectively, that is very high when compared to the CuS-5 h and CuS-20 h electrodes. As a result, from the detailed analysis, it is found that CuS as an excellent electrode material for high energy storage supercapacitor applications.

This paper presents an electrode with a core/shell geometry and a unique four-layered porous wrinkled surface for pseudocapacitive supercapacitor applications. To design the electrode, Ni foam was used as a substrate, where the harmonious features of four constituents, ZnO (Z), NiS (N), PEDOT:PSS (P), and MnO2 (M) improved the supercapacitor electrochemical performance by mitigating the drawbacks of each other component. Cyclic voltammetry and galvanostatic charge discharge measurements confirmed that the ZNPM hybrid electrode exhibited excellent capacitive properties in 2 M KOH compared to the ZNP, ZN, and solely Z electrodes. The ZNPM electrode showed superior electrochemical capacitive performance and improved electrical conductivity with a high specific capacitance of 2072.52 F g&minus, 1 at 5 mA, and a high energy density of 31 Wh kg&minus, 1 at a power density of 107 W kg&minus, 1. Overall, ZNPM is a promising combination electrode material that can be used in supercapacitors and other electrochemical energy conversion/storage devices.

High-performance PbS particles with cube-like structure were deposited onto fluorine-doped tin oxide glass substrates using a hydrothermal method. The PbS particles were used as an efficient counter electrode (CE) for polysulfide redox reactions in CdS/CdSe quantum dot-sensitized solar cells (QDSSCs). The deposition time and urea concentration were optimized to prepare the PbS CEs. The morphology becomes smoother and the surface roughness increases with the 0.3 M urea CE, which was confirmed by field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). Under full sunlight illumination, QDSSCs with the optimized 0.3 M urea CE achieved an efficiency of 3.83% (Voc = 0.55 V, Jsc = 13.17 mA cm−2, and FF = 0.52). This value is higher than those for the 0 M urea cell (η = 2.47%, Jsc = 10.60 mA cm−2) and Pt-based cell (η = 1.32%, Jsc = 5.85 mA cm−2). Characterization by electrochemical impedance spectroscopy (EIS) and Tafel polarization indicated that the PbS cube-like CEs have lower charge transfer resistance at the CE/electrolyte interface (RCE) and superior electrochemical catalytic ability. However, RCE increased with increasing urea concentration (urea >0.3 M), and therefore, the fill factor decreased for the PbS CEs. The influence of different urea concentrations is discussed in detail.

A cost-effective and uniform crystal with different structures was fabricated using a facile chemical bath deposition technique for electrochemical supercapacitor (SC) applications. In this study, CuS, PbS, and CuS@PbS composite electrodes were fabricated for SCs. The morphology and structure of the electrodes were analyzed by field emission&ndash, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The CuS@PbS composite electrode delivered outstanding electrochemical performance in SCs with a high specific capacitance of 1004.42 F g&minus, 1 at a current density of 2.85 A g&minus, 1, good cycling stability (only 2.9% loss after 3000 cycles at 2.85 A g&minus, 1), higher energy density of 33.89 Wh kg&minus, 1 at a power density of 714.28 W kg&minus, 1, and an excellent rate capability compared to other electrodes. These results show that the CuS@PbS composite can be used to improve the surface morphology and is a promising positive electrode material for SC applications.