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Metal sulfides (MS) and mixed metal sulfides (MTMS) have been considered potential candidates over their metal oxide/mixed metal oxide counterparts in recent years. Herein, one MTMS, i.e., NiCo 2 S 4 , was combined with 2D MS MoS 2 through a single-step solvothermal process with different morphologies (sheet-like and rod-like) for supercapacitor applications. The resulting electrode exhibited excellent coulombic efficiency, high specific capacitance, superior energy density, and, most importantly, ultra-high cycling stability. In particular, the electrode delivered a capacitance of 2594 F g -1 at 0.8 A g -1 after 45,000 charge/discharge cycles with a remarkable stability of 192%. Moreover, the corresponding hybrid supercapacitor device displayed an impressive coulombic efficiency of 123% after 20,000 cycles and 118% after 45,000 cycles. In addition, the device also exhibited a decent energy density of 31.9 Wh kg -1 and good cycling stability of 102% over 15,000 cycles.

Regular water quality measurements are essential to the public water supply. Moreover, selective free chlorine (disinfectant) level monitoring without an interfering agent is necessary. The present work aimed to fabricate poly(caffeic acid) (p-CFA) coated on an electrochemically reduced graphene oxide (ERGO) surface for the selective detection of free chlorine. Electron microscopy and various spectroscopic techniques confirmed the p-CFA@ERGO/glassy carbon (GC) electrode. The p-CFA@ERGO/GC coated probe surface coverage was calculated to be 4.75 × 10 -11 mol cm -2 . The p-CFA@ERGO/GC showed superior catechol/ o -quinone oxidation/reduction peaks for electrocatalytic free chlorine determination. The performance of the developed sensor electrode was outstanding, with an extensive range of free chlorine detection (20 μM to 20 mM), high sensitivity (0.0361 µA µM -1 ), and low detection limit (0.03 µM). The p-CFA@ERGO/GC capability of the realist water samples, such as the tested commercial and tap water, yielded a good range of recovery (from 98.5% to 99.9%). These values align with the standard N,N '-diethyl- p -phenylenediamine reagent method results.

The feasibility of achieving in situ sulfur (S) and nitrogen (N) co-doped carbon nano-onions (CNOs and SN-CNOs) via a simple flame-pyrolysis technique without using sophisticated high-vacuum annealing or expensive nanodiamond-based complex processes is demonstrated for the first time. The characteristic onion-like feature of 0.34 nm remained intact with a high degree of ordering and graphitization, even though the S and N heteroatoms were co-doped simultaneously. The in situ co-doped SN-CNO demonstrated high supercapacitor device performance with a high energy density of 25 Wh kg -1 at a maximum power density of 18 kW kg -1 , maintaining 98% specific capacitance over 10,000 cycles at 10 A g -1 . These are the highest achieved device performance values of a fullerene family electrode material to date.

Transition metal oxide aerogels are a fascinating class of compounds that have received considerable attention in the last decade owing to their unique and exceptional properties, including high porosity, large surface area, and ultralow density. In this study, α-Ni(OH) 2 aerogels and annealed NiO/Ni aerogels were used to design and fabricate a two-electrode supercapacitor device. The physicochemical properties of the as-synthesized aerogels were characterized through X-ray diffraction, scanning electron microscopy, transmission electron microscopy, the Brunauer-Emmett-Teller theory, and X-ray photoelectron spectroscopy studies. The annealed NiO/Ni aerogels showed a (specific capacitance of 1060 F/g) specific capacity of 422 C/g at 1 A/g current density and with good cycling stability (up to 10,000 cycles). The supercapacitor also demonstrated an energy density of 32.4 Wh/kg and power density of 1800 W/kg at a current density of 2 A/g. The specific capacitance of NiO/Ni aerogels was more than twice that of the α-Ni(OH) 2 aerogels. The practical applications of the aerogel were demonstrated by fabricating a two-electrode device.

To overcome the issues related to supercapacitor (SC) electrodes, such as high cost, low specific capacitance ( C s ), low energy density (ED), requirements for expensive binder, etc., binderless electrodes are highly desirable. Here, a new ternary nanohybrid is presented as a binder-free SC electrode based on Ni 3 S 2 , CoMoS 4 , and MnO 2 . A facile two-step hydrothermal route, followed by a short thermal annealing process, is developed to grow amorphous polyhedral structured CoMoS 4 and further wrap MnO 2 nanowires on Ni foam. This rationally designed binder-free electrode exhibited the highest C s of 2021 F g -1 (specific capacity of 883.8 C g -1 or 245.5 mAh g -1 ) at a current density of 1 A g -1 in 1 M KOH electrolyte with a highly porous surface morphology. This electrode material exhibited excellent cycling stability (90% capacitance retention after 4000 cycles) due to the synergistic contribution of individual components and advanced surface properties. Furthermore, an aqueous binder-free asymmetric SC based on this ternary composite exhibited an ED of 20.7 Wh kg -1 , whereas a solid-state asymmetric SC achieved an ED of 13.8 Wh kg -1 . This nanohybrid can be considered a promising binder-free electrode for both aqueous and solid-state asymmetric SCs with these remarkable electrochemical properties.

Energy consumption and environmental pollution are major issues faced by the world. The present study introduces a single solution using SnS 2 for these two major global problems. SnS 2 nanoparticles and thin films were explored as an adsorbent to remove organic toxic materials (Rhodamine B (RhB)) from water and an alternative to the toxic cadmium sulfide (CdS) buffer for thin-film solar cells, respectively. Primary characterization tools such as X-ray photoelectron spectroscopy (XPS), Raman, X-ray diffraction (XRD), and UV-Vis-NIR spectroscopy were used to analyze the SnS 2 nanoparticles and thin films. At a reaction time of 180 min, 0.4 g/L of SnS 2 nanoparticles showed the highest adsorption capacity of 85% for RhB (10 ppm), indicating that SnS 2 is an appropriate adsorbent. The fabricated Cu(In,Ga)Se 2 (CIGS) device with SnS 2 as a buffer showed a conversion efficiency (~5.1%) close to that (~7.5%) of a device fabricated with the conventional CdS buffer, suggesting that SnS 2 has potential as an alternative buffer.

Mixed metal sulfides exhibit outstanding electrochemical performance compared to single metal sulfides and mixed metal oxides because of their richer redox reactions and high electronic conductivity. In the present study, Zn-Co-S nanostrip cluster arrays were formed from ZnCo 2 O 4 grown on Ni foam by an anion exchange reaction using a two-step hydrothermal process. Morphological characterization confirmed that the Zn-Co-S nanostrip cluster arrays had grown homogeneously on the skeleton of the 3D Ni foam. The length of the nanostrip was approximately 8 µm, and the width ranged from 600 to 800 nm. The Ni foam-supported Zn-Co-S nanostrip cluster arrays were assessed directly for electrochemical supercapacitor applications. Compared to ZnCo 2 O 4 , the Zn-Co-S electrode exhibited a three-fold higher specific capacity of 830 C g -1 at a specific current of 2.0 A g -1 . The higher polarizability, lower electro-negativity, and larger size of the S 2- ion played an important role in substituting oxygen with sulfur, which enhanced the performance. The Zn-Co-S//AC hybrid device delivered a maximum specific energy of 19.0 Wh kg -1 at a specific power of 514 W kg -1 . The remarkable performance of Zn-Co-S nanostrip cluster arrays highlights their potential as a positive electrode for hybrid supercapacitor applications.

A graphene-cadmium sulfide (Gr-CdS) nanocomposite was prepared by a chemical solution method, and its material properties were characterized by several analysis techniques. The synthesized pure CdS nanoparticles (NPs) and Gr-CdS nanocomposites were confirmed to have a stoichiometric atomic ratio (Cd/S = 1:1). The Cd 3d and S 2p peaks of the Gr-CdS nanocomposite appeared at lower binding energies compared to those of the pure CdS NPs according to X-ray photoelectron spectroscopy analyses. The formation of the Gr-CdS nanocomposite was also evidenced by the structural analysis using Raman spectroscopy and X-ray diffraction. Transmission electron microscopy confirmed that CdS NPs were uniformly distributed on the graphene sheets. The absorption spectra of both the Gr-CdS nanocomposite and pure CdS NPs thin films showed an absorption edge at 550 nm related to the energy band gap of CdS (~2.42 eV). The Cu(In,Ga)Se 2 thin film photovoltaic device with Gr-CdS nanocomposite buffer layer showed a higher electrical conversion efficiency than that with pure CdS NPs thin film buffer layer. In addition, the water splitting efficiency of the Gr-CdS nanocomposite was almost three times higher than that of pure CdS NPs., Competing Interests: The authors declare no conflict of interest.