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In this work, we designed a straightforward and highly reproducible synthetic methodology to prepare Ru0–Pt0 composites. We report a significant improvement in the electrocatalytic performance upon compositing Ru with a very trace amount of Pt. In particular, Ru nanoparticles were derived from a Ru-Prussian blue analogue (Ru PBA) and composited with (0.1, 0.5, and 1 mmol) metallic platinum following an optimized chemical reduction method. Interestingly, the composite with 0.5 mmol of Pt (Ru@C/Pt0.5) required low overpotentials of 32 and 140 mV to achieve current densities of 10 and 100 mA cm−2, respectively. Furthermore, Ru@C/Pt0.5 exhibited a smaller Tafel slope (26 mV dec−1), robust durability with 50 hours of long-term stability and a higher turnover frequency (TOF: 5.6 s−1@η10 mA cm−2) than commercial Pt/C (TOF: 4.1 s−1@η10 mA cm−2). First-principles calculations using density functional theory (DFT) revealed that the existence of Pt islands on the Ru nanoparticles weakened the strength of the adsorption of hydrogen at the Ru interstitials due to electrostatic repulsion caused by charge retention at Ru atoms near the corner of the islands, leading to rapid dissociation of hydrogen. This created a significant impact on the improvement of the electrocatalytic HER activity of the Ru@C/Pt0.5 electrocatalyst. It appears that restricting the concentration of Pt to trace amounts is a necessary condition for the observed catalytic efficiency, as the catalytic efficiency decreases with an increasing island size due to stronger binding of atomic hydrogen on peripheral Pt atoms and stabilization of adsorbed atomic hydrogen caused by softening of phonon modes with increasing island size. This study opens up a novel avenue for the exploration of highly efficient electrocatalysts for hydrogen evolution reactions. [ABSTRACT FROM AUTHOR]

Transition metal sulfides have become famous in high energy density supercapacitor materials owing to their rich redox and high conductivity. While their development has achieved a breakthrough in terms of capacitance, there is little knowledge from the theoretical perspective on how dopants play a role in enhancing their capacitances. In this work, pseudocapacitance and quantum capacitance were evaluated through first-principles calculation to describe their role in transition metal sulfide, which here is represented by copper sulfide (CuS). The resulting quantum capacitance (CQ) was calculated in both the bulk and surface of CuS to determine which structure has a greater effect on the capacitance of the system. It was observed that the dopant increased CQ in the bulk system, which is different from the CQ of surface structures. Meanwhile, K+ ions were introduced on the surface structure to calculate transfer charge and work function shift, thus determining pseudocapacitance. All dopant types were able to increase the pseudocapacitance value, with Fe doping showing the highest capacitance of 111 F g−1, which is higher than that of the pristine structure (47 F g−1). The role of the dopant is discussed in detail in this work. Our results suggest that the increased capacitance of doped TMS materials was originated not only from the geometrical perspective but also from the higher pseudocapacitance value. Quantum capacitance, alternatively, could also contribute to the system when the dopant occurs in the bulk rather than only in the surface structure. This work may open a new perspective on how dopants play a role in increasing supercapacitor performance. [ABSTRACT FROM AUTHOR]

Vanadium nitride is a typical pseudocapacitive material that has attracted much attention among electrode materials as a result of its high theoretical capacity and wide voltage window. Nevertheless, its poor rate capability, cycling stability, and dissolution in alkaline electrolytes have restricted its practical applications. In this work, these problems are addressed by utilizing melamine-assisted pyrolysis and a dual-carbon composite strategy. A structurally controllable clustered shuttle vanadium-MOF is selected as the precursor. By subjecting it to high-temperature pyrolysis, melamine-derived carbon is coated on the surface of the vanadium-MOF, resulting in the formation of vanadium nitride-doped carbon electrode materials. Interestingly, they have a capacity of 407.5 F g−1 at a current density of 0.5 A g−1, with a capacity retention of 82.02% and a Coulombic efficiency of 80.59% after 10 000 cycles at a current density of 3 A g−1. When assembled into a device, the device shows a power density of 775 W kg−1 and an energy density of 39.29 W h kg−1. It is worth noting that the energy density reaches 15.82 W h kg−1 when the maximum power density of 3, 875 W kg−1 is attained. These anode materials have broad applications in energy storage systems, providing an innovative approach to developing new materials. [ABSTRACT FROM AUTHOR]

Rare earth element doped bimetallic oxides are a new technology for improving the electrochemical performance of electrode materials. In this study, 0.5% La-NiMoO4 flower-like structured nanomaterials were directly grown on nickel-based surfaces through a fast and simple room temperature stirring method. The characterization methods such as SEM and TEM confirmed that the prepared product has a three-dimensional nanoflower-like structure, and also demonstrated that the prepared 0.5% La-NiMoO4 nanoflower material was successfully doped with rare earth elements. We also conducted electrochemical tests on the material, and the results showed that at a reaction time of 16 h, the 0.5% La-NiMoO4 flower-like structure exhibited excellent electrochemical performance. At a current density of 2 A g-1, the specific capacitance was 2100 F g-1. After 5500 cycles of charging and discharging at a current density of 1 A g-1, the capacitance retention rate was 99.8%. A 0.5% La-NiMoO4/Ni//Fe2O3/Ni asymmetric supercapacitor device was assembled using 0.5% La-NiMoO4 as the positive electrode and Fe2O3 as the negative electrode. At a current density of 15 A g-1 and a working window voltage of 1.8 V, the power density of the asymmetric device was 8000 W kg-1 (energy density 56.5 W h kg-1). At a current density of 5 A g-1, the device underwent 5000 cycles of charge and discharge, and the capacitance retention rate was 89.5%. The 0.5% La-NiMoO4 electrode material prepared in this study through a simple, fast, environmentally friendly method exhibits good electrochemical performance, making it a potential electrode material for development. [ABSTRACT FROM AUTHOR]

Multi-component metal sulfide heterostructures possess a modulated electronic structure, abundant active sites and various morphology features, which are kinetically beneficial for fast electron/ion transport to enhance the energy storage performance. Herein a novel NiMoS4@Co9S8/Ni3S2 core–shell heterostructure is designed and constructed, which consists of Co9S8/Ni3S2 heterogeneous hollow nanotubes as the core and NiMoS4 nanospheres as the shell. The hierarchical NiMoS4@Co9S8/Ni3S2 array has the merits of each component and exhibits excellent electrochemical performance due to the synergistic effect. When examined as the supercapacitor electrode, an area specific capacitance of 9.61 F cm−2 was provided at a current density of 2 mA cm−2. In addition, the assembled asymmetric supercapacitor device achieves superior properties regarding high energy density of 0.44 mW h cm−2 at a power density of 2.30 mW cm−2 and good durability with 82.67% capacitance retention over 5000 cycles. This work sheds light on the design and construction of multi-component heterostructure with well-defined hollow core–shell morphology, which is an effective strategy to fabricate electrode materials for high performance energy storage devices. [ABSTRACT FROM AUTHOR]

Electrocatalytic high-throughput seawater electrolysis for hydrogen production is a promising green energy technology that offers possibilities for environmental and energy sustainability. However, large-scale application is limited by the complex composition of seawater, high concentration of Cl− leading to competing reaction, and severe corrosion of electrode materials. In recent years, extensive research has been conducted to address these challenges. Metal nitrides (MNs) with excellent chemical stability and catalytic properties have emerged as ideal electrocatalyst candidates. This review presents the electrode reactions and basic parameters of the seawater splitting process, and summarizes the types and selection principles of conductive substrates with critical analysis of the design principles for seawater electrocatalysts. The focus is on discussing the properties, synthesis, and design strategies of MN-based electrocatalysts. Finally, we provide an outlook for the future development of MNs in the high-throughput seawater electrolysis field and highlight key issues that require further research and optimization. [ABSTRACT FROM AUTHOR]

Iron disulfide or pyrite (FeS2) has emerged as a promising transition metal sulfide-based supercapacitor owing to its abundance and superb electrochemical properties. However, FeS2 still faces major hurdles in realizing its full potential, such as a low energy density and poor conductivity. In this study, we report a high-performance FeS2 supercapacitor synthesized by a direct one-step process with the help of polyvinylpyrrolidone (PVP). The incorporation of PVP on the active materials prevented dendritic expansion and acted as a binding for solving the current FeS2 limitations, while facilitating a one-step synthesis process. Additionally, PVP could enhance the electrochemical performance by enabling faster ion movement. An FeS2/PVP nanocomposite was successfully synthesized, and used in an asymmetric supercapacitor, demonstrating a high specific capacity of 735 F g−1 (at 2 A g−1) and a high energy density of 69.74 W h kg−1 (at 911 W kg−1). The superior electrochemical properties of FeS2/PVP were enabled by the lower charge-carrier resistance and better surface passivation by PVP, as demonstrated by both electrochemical experiments and first-principles calculations. The high-performance supercapacitor of FeS2 presented in this study synthesized in situ by an efficient method provides a new insight into novel supercapacitor electrodes. [ABSTRACT FROM AUTHOR]

Developing high-efficiency electrode materials is of great importance in manufacturing supercapacitor devices with superior electrochemical performance. Herein, we for the first time report a binder-free method for controllable growth of Cu3N electrode materials via magnetron sputtering for supercapacitor applications. Benefiting from their unique polyhedral structure and good electrical conductivity, Cu3N electrodes can achieve an areal capacity of 90.7 mC cm−2 at 1 mA cm−2 and outstanding cycling stability with a capacity retention of 97.4% after 20 000 cycles. In particular, the assembled Cu3N//active carbon quasi-solid-state asymmetric supercapacitor can exhibit a maximum energy density of 13.2 μW h cm−2 and a power density of 4.8 mW cm−2 with an operating voltage of 1.6 V. These remarkable performances demonstrate the great potential of sputtered Cu3N electrode materials for future energy storage applications. [ABSTRACT FROM AUTHOR]

Electrode materials are the key to defining the overall electrochemical performance of energy storage devices and have been an essential hot topic for decades. This study synthesized MnSe-based ZnO composites with MnSe weight ratios (10 and 40%) denoted as ZK-1 and ZK-2 using a simple, cost-effective and economical wet-chemical technique. It investigated their electrochemical characteristics for high-performance hybrid supercapacitors. The comparatively lower resistance of MnSe than that of ZnO (2.40 Ω and 1.45 Ω, respectively) and ZK-2 relative to ZK-1 (1.10 Ω and 0.8 Ω, respectively) give the evident advantages of an improved capacitive energy storage performance owing to their fast faradaic redox reactions due to Mn3+/Mn4+, superior charge storage process, good reversibility and high capacitances of 470 F g−1 and 680 F g−1 at low current rates, respectively. More specifically, at 12 000 cycles, an extraordinarily steady cycling stability of 95.5% was achieved, with a superior energy and power supply of 57.8 W h kg−1 at 13 005 W kg−1 and deficient solution and charge transfer resistance of 1.3 and 6.4 when built as a ZK-2‖AC hybrid supercapacitor. The capacitance, energy and power densities, and low resistance prove the synergistic effect between the MnSe and ZnO nanostructures in a hybrid supercapacitor. Notably, a stable voltage window of 1.75 V in an aqueous solution as an electrolyte boosts the capacitance and power delivery, and thus these seem to be promising electrode materials for advanced hybrid supercapacitors. [ABSTRACT FROM AUTHOR]

It is a reality that the world's growing energy resource consumption will increase the demand for materials made through recycling. The present study focuses on the production of new materials by recycling. The cathode of a discarded commercial Li-ion battery (LiCoO2) was used to produce a CoS-based supercapacitor electrode material. The leaching of LiCoO2 was done using 0.1 M H2SO4 aided by 1.0 M H2O2 at room temperature. After leaching, CoS was precipitated by the addition of Na2S. For the first time, the precipitation of Co2+ ions leached from the cathode material was accomplished utilizing Na2S as a sulfur source at room temperature and CoS was then used as an electrode material in a coin cell-type supercapacitor. The morphology and properties of the produced CoS were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), and Mastersizer analyses. The electrode used in the supercapacitor was formed by combining CoS, carbon black, and polyvinylidene fluoride (PVDF) as the binder in varying compositions. The active materials were coated on the graphite foil and an asymmetric-type supercapacitor device was produced using 2 M KOH as the electrolyte. Using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques, the electrochemical performances of supercapacitors were evaluated. In cyclic voltammetric analyses, the maximum potential range for supercapacitors was determined as −1.0 V to 1.0 V. The cycling performance of the supercapacitors was measured by CV analyses for 1000 cycles at 200 mV s−1. The highest specific capacitance was obtained from the C80 electrode as 70.5 F g−1 at a 1 A g−1 charge/discharge current density. [ABSTRACT FROM AUTHOR]

A series of pyrenyl and halogenated chalcone (PyBr and PyF) derivatives with different substituent groups have been constructed in this work for dye-sensitized solar cell (DSSC) applications. The compounds were synthesized using the Claisen–Schmidt condensation reaction and single crystals were successfully attained via the slow evaporation method. The existence of intermolecular interactions (C–H⋯O, C–H⋯π and π⋯π) in crystal packing was found to stabilize the crystal structure and enhance charge transfer within the molecules. UV-Vis analysis was conducted with the acetonitrile solvent to obtain the energy gap values of PyBr and PyF, which were particularly in the range suitable for photosensitizer materials used in DSSC (2.74 and 2.78 eV). The proposed compounds are situated in the appropriate HOMO and LUMO energy levels, confirming their suitability as dye sensitizer materials. Further, all compounds were investigated for solar cell performance. The fabrication of the DSSC layers was carried out and characterization using the FESEM-EDX analysis revealed the surface morphology and elemental composition of the compounds on the TiO2 layer. Owing to the D–π–A architecture and planar structure of PyBr, the compound showed an improved performance in DSSC compared with the twisted structure of PyF with the additional methoxy group. [ABSTRACT FROM AUTHOR]

The inconsistent characteristics of renewable energy sources have led to a continual imbalance between the need and supply of energy. Therefore, developing adequate energy-storage devices might be one solution to this ongoing issue. Supercapacitors are considered as predominant energy storage technologies and power sources to fulfil the energy demands of the modern lifestyle. The present article reports a simple one-pot hydrothermal route to prepare flower-like MoS2/rGO (MG) nanohybrids followed by impregnation on nickel foam to develop the electrode for supercapacitors. The resultant MG-2 nanohybrid possessed a maximum specific capacitance of 2049.90 F g−1 at a current density of 30 mA g−1 and approximately 100% capacitive retention up to 10 000 successive charge–discharge cycles at 660 mA g−1. Quantitative estimations were made to give detailed information on the contribution of the surface capacity and diffusion response to the overall charge-storage mechanism. In addition, a symmetric supercapacitor cell was designed using MG-2 nanohybrid electrodes, which achieved a high specific energy of 192.43 W h kg−1 and specific power of 337.36 W kg−1. The remarkable electrochemical properties were attributed to the peculiar morphology of MG-2 nanohybrid having a distinctive 2D microstructure and minimal equivalent series resistance. [ABSTRACT FROM AUTHOR]

Hydrothermal synthesis and annealing process were used to create a honeycomb-structured composite electrode material on nickel foam substrate that contained praseodymium oxide (Pr2O3), cobalt oxide (Co3O4), and reduced graphene oxide (rGO) (named as Pr2O3/Co3O4/rGO/NF). The Pr2O3/Co3O4/rGO/NF (PCGN) composite electrode material was created without the need for a binder and can be employed right away to create a supercapacitor. This honeycomb composite is further grown by the mesh structure of Pr2O3 and Co3O4, which has good electrical conductivity. This nanomorphology not only improves the specific surface area of the material but also facilitates the improvement of electron transfer efficiency. The synthesized electrode material has excellent electrochemical properties due to its special morphology and excellent conductivity, and its performance is better than that of praseodymium oxide and cobalt oxide alone, with a specific capacitance of 3316 F g−1 in the three-electrode system at a current density of 1 A g−1. After forming a symmetrical supercapacitor device, the energy density is 74.8 W h kg−1 and the power density is 300 W kg−1 at 0.5 A g−1. The capacitance retention is 82% even after 35 000 cycles at 2 A g−1. [ABSTRACT FROM AUTHOR]

Supercapacitors are among the most promising energy storage devices; they exhibit a larger power density than batteries but a poor energy density. To meet the ever-increasing demands for energy, it is crucial to develop novel materials that improve the energy storage efficiency. Recent studies have focused on the use of different electrode materials in supercapacitors. Transition metal nitrides offer enormous potential in terms of energy storage because of their layered structure and high electrical conductivity, which promote promising properties in terms of stability, energy and power density, and lifetime. This review elaborates on the recent advances in transition metal nitrides. The different synthesis methods and different transition metal nitrides have been discussed and the electronic structure engineering strategies such as heteroatom-doped metal nitride, heterostructure metal nitride, and multi-metal nitride, have been focused on, which help improve the electrochemical performance of supercapacitors. Finally, the challenges, future direction, and perspectives of transition metal nitride for future direction have been discussed. [ABSTRACT FROM AUTHOR]

The porous flower-like microsphere structure composite of gadolinium oxide (Gd2O3), tricobalt tetraoxide (Co3O4) and reduced graphene oxide (rGO) was prepared on the nickel foam (NF) substrate by a hydrothermal synthesis method and annealing process, which can be directly used as an electrode material for supercapacitors without any conductive adhesive or binder. This porous nanostructure not only improves the conductivity of the electrode, but also shortens the migration route of ions and electrons. The innovative electrode of Gd2O3/Co3O4/rGO/NF has a high specific capacitance of 3616 F g−1 (1 A g−1). The supercapacitor is assembled, with a specific capacitance of 442.5 F g−1 (0.5 A g−1) at room temperature (20 °C) and strong multiplicative performance (current density from 0.5 to 20 A g−1, specific capacitance retention of 65.9%). At a power density of 300 W kg−1, the energy density reaches 88.5 Wh kg−1, and the performance stays relatively stable across a large working temperature range of 0 to 60 °C. The specific capacitance is 368.3 F g−1 even at temperatures up to 60 °C and 415.0 F g−1 at temperatures below 0 °C. Even after 40 000 cycles at a high current density of 10 A g−1, the capacity retention is 93.3%, suggesting exceptional cycling stability. This study demonstrates the potential practical application of Gd2O3/Co3O4/rGO/NF electrodes in supercapacitors. [ABSTRACT FROM AUTHOR]

The core–shell structured CuO@NiCoMn-LDH electrode was synthesized by wet chemistry, calcination, and electrodeposition. The synergistic effect of CuO nanowires and NiCoMn-LDH nanosheets has a significant enhancement effect on electrode materials. At the same time, the Mn content plays a decisive role in regulating and optimizing the morphology and electrochemical performance of electrode materials. The optimized CuO@NiCoMn-LDH, a binder-free electrode, exhibits excellent electrochemical performance. It displays a high specific capacity of 2.66 mA h cm−2 (20.7 F cm−2, 336.71 mA h g−1) at 10 mA cm−2 and satisfactory cycling stability (under a current density of 30 mA cm−2, after 3000 cycles, the capacity retention rate is 94.82%). In addition, an asymmetric supercapacitor (ASC) is built using the CuO@NiCoMn-LDH electrode as the positive electrode and Fe3O4@C/CuO electrode as the negative electrode to demonstrate its practical applicability in energy storage devices. At a power density of 4.79 mW cm−2, the ASC device can achieve a maximum energy density of 2.67 mW h cm−2. Two ASC devices are used as the power source of the light emitting diode (LED), which can emit light continuously for 15 minutes, showing great potential in energy storage device applications. [ABSTRACT FROM AUTHOR]

Supercapacitors are widely accepted as one of the energy storage devices in the realm of sustainable and renewable energy storage. Supercapacitors have emerged as a good alternative to traditional capacitors and fuel cells due to their higher energy density and power density compared to batteries and fuel cells. However, supercapacitors have some drawbacks such as low energy density and poor cycle life compared to batteries. To overcome these issues, researchers are paying much attention to the fabrication of metal oxide nanostructures and their modification by different approaches such as doping, introducing oxygen vacancies, and hybridization with nanomaterials of carbon allotropes for enhanced electrochemical properties. In this review article, we have presented the above-mentioned topics with the aid of recently reported works. Moreover, we have provided theoretical insights from density functional theory for the electrochemical behavior of the electrode materials from the published works. This review concisely presents the advancement in the supercapacitor energy storage field and the different approaches involved in the fabrication of supercapacitor electrode materials, which will be very handy to the researchers working in the field of energy storage. Further, the challenges and future perspectives of this exciting research field are discussed in detail. [ABSTRACT FROM AUTHOR]

Recently, metal nitrides (MNs) have received renewed attention due to their potential as catalytic materials in energy transformations, with water spitting and CO2 reduction being the most studied reactions. Reactions considered in this review are limited to photocatalysis. Moreover, the morphology, size, defects and nanostructured construction of MNs are demonstrated to be critical factors in their catalytic efficiency, emphasizing the importance of their synthetic method. Mono, binary, ternary and doped nanostructured MN materials have been synthesized and evaluated as photocatalysts. The latest research is focused on the development of new synthetic methods, cocatalysts, and constructure design, aiming to achieve improved activity, selectivity, and stability. This review provides a broad overview of the development of photocatalysts for the generation of H2 and CO2 reduction reaction, summarizing the current state of work focusing on the recent progress in light-induced overall water splitting and CO2 reduction on metal nitride photocatalysts. [ABSTRACT FROM AUTHOR]

After in situ selenylation, hydrothermally synthesized NiMoO4 was partially converted to NiSe2 and MoSe2, and the obtained NiMoO4/NiSe2/MoSe2 nanowires were used as a supercapacitor electrode material. The specific capacitance of the nanowired NiMoO4/NiSe2/MoSe2 was significantly higher than that of NiMoO4 at a current density of 1 A g−1 (955 vs. 489 F g−1). NiMoO4/NiSe2/MoSe2 also exhibited a high capacitance retention of 86.1% after 5000 cycles at 10 A g−1. The high supercapacitive performance of NiMoO4/NiSe2/MoSe2 can be ascribed to the obvious heterointerfaces, rich defects and remarkably increased electrical conductivity after in situ selenylation of NiMoO4. [ABSTRACT FROM AUTHOR]

Nickel sulfide (Ni3S2) has been widely known in the energy storage field, owing to the high theoretical capacitance, low cost, and environmental friendliness. We reported simple, low-cost hydrothermal synthesis of Ni3S2 nanoparticles as a remarkable electrode material for symmetric supercapacitor (SSC) in this paper. The structural characterization confirms the successful formation of the sample with a nanoparticle-like morphology with good crystallinity. The unique structure is composed of plenty of ion mobilization channels that exhibits superb electrochemical performance. When employed as an electrode material for supercapacitors, the fabricated Ni3S2 nanoparticles displayed the typical features of battery-type faradic electrodes showing an ultra-high specific capacitance of 2495 F g−1 at 1 A g−1 and excellent cycling stability (92.2% capacitance retention after 5000 consecutive CV cycles) within the potential frame of −0.2 to 0.6 V in a three-electrode system, which surpasses many previous literature reports. In the end, a SSC device was assembled exhibiting an optimized and stable potential window of 1.8 V with a high specific capacitance of 116.6 F g−1 at 5 A g−1. Moreover, the Ragone plot shows a high energy density of 52.4 W h kg−1 and an ultra-high power density of 13 500.0 W kg−1, indicating excellent cycling stability (95% retention after 7000 cycles). Additionally, we demonstrated a coin-type SSC that provides sufficient energy to turn on the red LED, which emits light over a certain period to open up possible realistic applications. These results show the great potential of Ni3S2 nanoparticles in the development of high-performance electrode materials for energy storage and conversion systems. [ABSTRACT FROM AUTHOR]

Capacitors began their journey in 1745, and to date have advanced in the form of supercapacitors. Supercapacitors are one of the advanced forms of capacitors with higher energy density, bridging capacitors and batteries. The energy storage through the formation of an electrical double layer is pivotal for supercapacitor technology. Accordingly, to further improve the energy density, surface faradaic (pseudocapacitive) processes are employed, and henceforth, the journey of chemical supercapacitors commenced. Herein, the materials, mechanisms and fabrication of chemical supercapacitors based on metallic compounds and conducting polymers are discussed in detail. The inherent limitations of these materials are addressed, and the feasible mitigation measures are identified. Poor conductivity, slow diffusion kinetics and rapid structural disintegration over cycling are the common constraints of metallic compounds, which can be overcome by preparing conductive nanocomposites. Thus, versatile conductive nanocomposites of metal oxides, hydroxides, carbides, nitrides, phosphides, phosphates, phosphites, and chalcogenides are elaborated. A lack of structural integrity is the prime obstacle for the realization of conducting polymer-based supercapacitors, which may be solved by forming composites with robust support from carbonaceous materials or metallic compounds. Consequently, the composites of polyaniline, polypyrrole, polythiophene and polythiophene-derivatives are discussed. The historical accounts of early stages of works are emphasised in order to review the developmental pathways of chemical supercapacitors. The construction of full cells and their performance data are presented herein, which synchronize the behaviour of practical scaled-up devices. To the best of our knowledge, this review is the first holistic description of chemical supercapacitors based on metallic compounds and conducting polymers from the first reports to recent advancements. [ABSTRACT FROM AUTHOR]

Transition metal nitrides (TMNs), by virtue of their unique electronic structure, high electrical conductivity, superior chemical stability, and excellent mechanical robustness, have triggered tremendous research interest over the past decade, and showed great potential for electrochemical energy conversion and storage. However, bulk TMNs usually suffer from limited numbers of active sites and sluggish ionic kinetics, and eventually ordinary electrochemical performance. Designing nanostructured TMNs with tailored morphology and good dispersity has proved an effective strategy to address these issues, which provides a larger specific surface area, more abundant active sites, and shorter ion and mass transport distances over the bulk counterparts. Herein, the most up-to-date progress on TMN-based nanomaterials is comprehensively reviewed, focusing on geometric-structure design, electronic-structure engineering, and applications in electrochemical energy conversion and storage, including electrocatalysis, supercapacitors, and rechargeable batteries. Finally, we outline the future challenges of TMN-based nanomaterials and their possible research directions beyond electrochemical energy applications. [ABSTRACT FROM AUTHOR]

Nickel sulfides (NS) occupy a vital position in the fields of catalysis and energy storage by virtue of their outstanding functional properties. Currently, NS are usually synthesized by solid-state sulfidation and gas-sulfidation methods that require long preparation periods and high energy consumption and wet chemistry approaches involving toxic reagents or solvents and tedious processing steps. Here, taking advantage of microwave plasma triggered by corona discharge, NS with controllable morphology can be synthesized in an ordinary household microwave oven within minutes via a solvent-free one-pot plasma reaction. The plasma with inherent high energy can significantly accelerate the reaction kinetics, thereby shortening the synthetic process and cutting the energy costs. When used as freestanding lithium-ion battery cathodes, the synthesized stone-forest-like NS deliver high rate capacity and superior cycling stability simultaneously. This green method can also realize morphology-controllable synthesis of copper sulfides, and it can be foreseen that this eco-friendly, high-efficiency and low-cost strategy can be extended to other metal sulfides and other metal compounds such as phosphides, carbides and selenides, opening new avenues for green synthesis and materials design. [ABSTRACT FROM AUTHOR]

Batteries and supercapacitors are promising candidates for electrochemical energy storage while the development of their electrode materials is becoming a bottleneck. This limitation necessitates the design of electrode materials with high specific capacity/capacitance and excellent cycling stability, yet at a low cost. Herein, we present the research progress of magnetron sputtering enabled nanostructured materials as electrode materials for electrochemical energy storage. Firstly, magnetron sputtered anode materials (Si-based materials, metal-based materials, metal oxides, etc.) and cathode materials (i.e., transition metal oxides and phosphates) for lithium/sodium ion batteries are systematically reviewed. Secondly, magnetron sputtered electrode materials (metals and metal oxides, metal nitrides, etc.) for electrochemical supercapacitors are discussed. Furthermore, critical insights into the corresponding electrical conductivity and cycling stability of the electrode materials are provided through illustrations of how to rationally design and optimize electrode materials via magnetron sputtering technology. Finally, the emerging challenges and future directions of magnetron sputtered electrode materials for electrochemical energy storage are discussed. [ABSTRACT FROM AUTHOR]

In this work, Ru-based catalysts with the synthesized and commercial Mg(OH)2 and MgO as supports such as Ru/Mg(OH)2(S) (or Ru/Mg(OH)2(B), Ru/MgO(S), and Ru/MgO(B)), S and B representing "synthesized" and "commercial", respectively, were prepared at room temperature by a simple chemical reduction approach. The Ru/Mg(OH)2(S) catalyst exhibited the best catalytic activity (TOF = 134 h−1) and the highest selectivity to 1,2-propanediol (65%) for glycerol hydrogenolysis. Moreover, this reaction was performed over the as-prepared catalysts without adding any liquid acid (e.g., HCl) or base (e.g., NaOH). Selectivity of 1,2-propanediol increased with an increase in the reaction temperature or time, but that towards ethylene glycol did not show any obvious change. Characterization techniques such as XRD, SEM, XPS, TG, TEM, HRTEM, STEM, STEM-EDX elemental analysis (mapping and line-scanning), and CO2-TPD were used to explore related properties of the as-synthesized catalysts to explain the difference in their catalytic activity and selectivity. The reasons for Ru/Mg(OH)2(S) to exhibit high catalytic activity are as follows: Ru with high dispersion on the support, Mg(OH)2 with a cotton-like morphology, numerous defect sites and strong basic active sites. [ABSTRACT FROM AUTHOR]

The adsorption of metal ions and the further utilization of adsorbent materials help solve serious environmental pollution; therefore, transforming them into supercapacitor electrode materials could be a promising possibility. Here, we used pectin as a heavy metal ion adsorbent to prepare a series of vanadium-containing precursors, and different vanadium nitride and carbon composites were prepared via annealing with varied water contents in the precursors. By studying these composites, we found that the addition of water can effectively improve the final oxygen content of the product chemical oxygen, thereby improving the wettability or hydrophilicity of the composite material. Furthermore, hydrophilicity or wettability improves some electrochemical characteristics, particularly the voltage drop. Electrodes with a high voltage drop have poor hydrophilicity, and hence a systematic study from phenomena to mechanisms associated with voltage drop is conducted in detail. [ABSTRACT FROM AUTHOR]

Effective wastewater treatments are of great importance to contemporary scientists, because the existing methods are ineffective for detoxifying tannery wastewater. This study aims to synthesize and characterize the polysiloxane-immobilized thiosalicylic–mercaptoethanol biligand system (PITSMCBLS) and use it in the detoxification of Cr3+ and Fe3+ in tannery wastewater. Porous, solid PITSMCBLS was prepared by hydrolytic polycondensation of tetraethylorthosilicate with a mixture of 3-chloropropyltrimethoxysilane, methanol and sodium hydroxide as a catalyst. The gelation formed (3-CPP) after 40 min, was functionalized (F-3CPP) with excess ethylchloroacetate and triethylamine, and grafted with a thiosalicylic–mercaptoethanol biligand. The PITSMCBLS was characterized using FTIR and SEM-EDX. The competitive sorption characteristics of the metal ions (Cr3+ and Fe3+) were studied using microwave plasma atomic-emission spectrophotometry (MP-AES). The FTIR spectrum of PITSMCBLS showed vibrational frequencies (cm−1) at: 3339, (O–H); 2928, (C–H); 2685, (SH); 2497, (Si–H); 1587–1707, (C＝O) and 1028, (Si–O). The SEM-EDX results showed irregular particle sizes (4.4294 ± 1.7187 nm) and an elemental composition (wt%) for 3-CPP of Si (50.45), O (25.02) and Cl (24.57). The F-3CPP showed an elemental composition (wt%) of O (58.68) and Si (41.32), whereas PITSMCBLS showed 11.94 of S. The Gibbs free energy yielded negative values for ΔG° (Cr3+ −14.187 to −14.832 and Fe3+ −14.369 to −14.843 kJ mol−1), and positive values for ΔH° (Cr3+ 5.345 and Fe3+ 0.000 kJ mol−1) and ΔS° (Cr3+ 64.459 and Fe3+ 47.421 J mol−1 K−1), respectively. Use of PITSMCBLS exhibits high potential for the extraction of Cr3+ and Fe3+ from tannery wastewater. The thermodynamic values indicated spontaneous, endothermic reactions and a high degree of disorderliness with respect to the metal ion binding capacity to the ligand system. This development would improve tannery wastewater treatment. [ABSTRACT FROM AUTHOR]

As a series of important metal materials, rare earth elements and their related derivative compounds have received significant attention because of their narrow emission bands, noncytotoxicity, excitation of multiple fluorescence colors and electrochemical properties. These unique properties endow rare earth-based nanomaterials with great potential for application in various fields such as in supercapacitors, batteries, sensors, devices and solar cells. This review presents a general description of the electrochemical properties of rare earth-based nanomaterials. The developments and improvements of their electrochemical applications in electrochemical sensors for the detection of small biomolecules and DNA, supercapacitors, batteries and electrochemical catalysis towards the hydrogen evolution reaction have also been discussed. [ABSTRACT FROM AUTHOR]

Owing to the natural abundance and high safety, electrochemical sodium-ion storage and removal devices are considered as promising candidates for large-scale energy storage and water purification systems. When used as the key component of sodium ion batteries (SIBs), sodium ion hybrid capacitors (SIHCs), and capacitive deionization (CDI) devices, the electrode architecture and composition need to be precisely designed to achieve high capacity, rate performance, and long life span. Among various sodium hosting materials, titanium-based electrodes have been intensively investigated owing to their appropriate operating voltage, small strain expansion, fast rate capability, environmental friendliness, safety, and low costs. In this review, we discuss the progress of Ti-based electrode materials over the last two years, covering their classification and key factors (electrical conductivity, ion diffusion, volume variation, capacity and operating voltage) of the electrode design for SIB, SIHC, and CDI applications. The architectural concepts, synthesis methods, and microstructural and compositional control of Ti-based electrodes are also discussed. Our perspectives on current impediments and the future research direction are finally discussed. This review inspires us to propose new chemical strategies that can greatly improve the electrochemical performance. [ABSTRACT FROM AUTHOR]

To achieve high-energy density of supercapacitors and maintain their intrinsic high power density, the operating voltage should be extended by assembling high specific capacitance electrode materials into an asymmetric supercapacitor (ASC) device. Herein, an ASC was assembled based on a three-dimensional (3D) interconnected porous carbon framework (PRPC-1K) as a negative electrode and 3D sphere-like nickel nitride (Ni3N) nanosheets as a positive electrode in an aqueous KOH electrolyte. The PRPC-1K was prepared by a simple activation process with biomass poplar root as the carbon precursor, and the Ni3N nanosheets were successfully synthesized via a simple low-temperature hydrothermal and further urea-assisted nitridation process. Due to the unique structures and high capacitive performances of these materials, the Ni3N//PRPC-1K ASC assembled based on these two materials achieved the high energy density of 30.9 W h kg−1 at the high power density of 412 W kg−1 and acceptable electrochemical cycling stability with an 81% retention after 5000 cycles. [ABSTRACT FROM AUTHOR]

Pure and Mn2+ doped CuInSe2 thin films (Mn content: 1 to 5 mole%) were deposited on indium doped tin oxide (ITO) glass substrates by a single step electrochemical deposition method at low temperature (358 K). The as-deposited pure CuInSe2 thin films were irradiated with Au8+ ions (100 MeV) at room temperature and liquid nitrogen temperature with an ion fluency of 1 × 1014 ions per cm2. Glancing angle X-ray diffraction patterns showed that the as-deposited pure and Mn2+ doped CuInSe2 thin films and the irradiated thin films have a tetragonal crystal structure without any trace of secondary phases. Mn2+ doping does not alter the tetragonal structure of CuInSe2 thin films except for a strong (112) plane preferred orientation in all the doped thin films. The absorption coefficient's fall is sharper for 5 mole% Mn2+ doped and irradiated CuInSe2 thin films than for pure and 1 to 4 mole% Mn2+ doped CuInSe2 thin films due to better crystallinity. Magnetic measurements reveal that Mn2+ doping into the CuInSe2 lattice induces ferromagnetism. The electrical studies of Mn2+ doped and irradiated CuInSe2 thin films show that hole mobility and hole concentration increase with a slight decrease in resistivity. Mn2+ in CuInSe2 thin films acts as an acceptor and the original p-type conductivity is retained. The new antistructural modeling for describing the defects in the CuInSe2:Mn system shows that the dissolution of the Mn cations in the chalcopyrite matrix increases the hole concentration. Solar light irradiation with an intensity of 100 mW cm−2 on Mn2+ (5 mole%) doped and LNT irradiated CuInSe2 thin film-based cells resulted in a power conversion efficiency of 6.38 and 4.57%, respectively. [ABSTRACT FROM AUTHOR]