Search

In order to solve the problem of low energy density of previous cement-based supercapacitors, the capacitor performance was optimized in four aspects: positive electrode performance, positive and negative capacity matching, and electrolyte performance. The effects of electrodeposition solution ratio and scan rate on the electrochemical properties of nickel–cobalt double hydroxide were investigated. The microscopic morphology and elements of nickel–cobalt double hydroxide were analyzed by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The optimized nickel–cobalt double hydroxide electrode demonstrates an excellent areal capacitance of 10.53 F cm−2 and excellent cycling stability (106% capacitance retention after 10 000 cycles) at a current density of 1 mA cm−2. In this paper, an electrode made of activated carbon was used as the negative electrode and the loading of activated carbon was strictly controlled to better match the high specific capacitance of the nickel–cobalt double hydroxide electrode. An optimally proportioned cementitious-polymer electrolyte was selected as the electrolyte for the supercapacitor. The three-step optimized supercapacitor exhibits a high areal capacitance of 1.442 F cm−2, good cycle retention (69.4%), and a remarkable energy density of 0.444 mW h cm−2 (0.75 mW cm−2). This paper is expected to provide a new way to mitigate the issue of "curtailed light" and to construct large-scale buildings integrating light, electricity, and energy storage. [ABSTRACT FROM AUTHOR]

This study investigates the degradation of dark blue reactive azo (DBA) dye using the electro-Fenton process, with a focus on real-time colour monitoring to identify the most effective cathode–anode combinations for dye removal. Various electrode materials, including platinum (Pt), carbon fibre (C), silver (Ag), and copper (Cu), were tested. The combinations involving carbon fibre achieved a 75% colour removal within the first 20 minutes of electrolysis, whereas those with Pt electrodes did not exceed 15% in the same timeframe across different combinations. The results indicated that the carbon–copper (C–Cu) electrode combination, under optimized conditions, led to approximately 88% dye removal within 120 minutes. A kinetic study using a non-linear method demonstrated that the degradation followed a first-order kinetic model. To better understand the degradation mechanism, the degradation pathway of the DBA dye was predicted through a theoretical analysis using the Fukui function and supported by UV-Vis absorbance spectra, which revealed potential degradation by-products. The experimental data aligned with the theoretical spectra of potential by-products, confirming the electro-Fenton process's effectiveness in breaking down organic dye molecules. The study highlights the superior performance of carbon-based electrodes compared to platinum electrodes and underscores the importance of electrode material selection in optimizing the electro-Fenton process for dye degradation. [ABSTRACT FROM AUTHOR]

This manuscript presents a novel method to enhance the electrochemical performance of CaMoO4 for supercapacitors by synthesizing it from a bi-metallic metal–organic framework (MOF). The resulting CaMoO4 nanoparticles retain MOF characteristics, with a high surface area, and demonstrate improved performance over conventionally synthesized CaMoO4. Electrochemical tests showed the MOF-derived CaMoO4 achieved a high capacitance of 377.82 F g−1 at 1 A g−1 and retained 91% of its capacitance after 5000 cycles. The assembled asymmetric supercapacitor also retained 88% of its capacitance after 10 000 cycles, highlighting the potential of this approach for enhancing energy storage devices. [ABSTRACT FROM AUTHOR]

In this research, we explore the utilization of biomass-derived proteins, specifically from egg whites, as a novel carbon source for crafting silicon/nitrogen-doped carbon composites, aimed at overcoming the significant volume expansion issues associated with silicon electrode materials in lithium-ion batteries (LIBs). Egg whites, known for their high protein content, offer a sustainable reservoir of carbon and nitrogen, essential for enhancing the electrochemical performance of silicon-based electrodes. Leveraging the unique structural transformation induced by whipping egg whites—resulting in a foamy material with distinct properties—we blend this with micron-sized silica powder. This mixture is then subjected to a straightforward carbonization process, yielding silicon–carbon composites enveloped in nitrogen-doped amorphous carbon layers. Our findings demonstrate that these Si–N–PC composites, when used as anodes in LIBs, deliver a commendable reversible capacity of 814 mA h g−1 over 100 cycles at a current density of 1 A g−1. The incorporation of nitrogen-doped carbon layers significantly improves lithium-ion diffusion, mechanical stability, and overall electrochemical performance of the electrode material. This approach not only simplifies the production process but also aligns with environmentally friendly practices. Given these results, we posit that our method could serve as a viable blueprint for the mass production of next-generation energy materials, addressing both performance and sustainability concerns. [ABSTRACT FROM AUTHOR]

Electrochemical oxidation is an energy-efficient and environmentally friendly reaction mode, but it is limited by the difficulty of fabricating electrode systems that can efficiently perform high-yield oxidation reactions at low potentials. Herein, we prepared V–N supported electrocatalysts with nickel foam as the electrode substrate (VO-N/NF nanocomposite) for electrocatalytic benzyl alcohol oxidation by a one-step hydrothermal method. Specifically, the VO-N/NF nanocomposite electrode can reach a current density of 100 mA cm−2 at a low voltage of 1.395 V (vs. RHE) in 1.0 M KOH electrolyte with only 0.2 mmol metal precursor. The synergistic effect of high-valent nickel-based compounds, as well as the exposed active sites resulting from the dissolution of V elements in the process, makes it super-efficient and profitable for electrocatalytic oxidation. The best proof is that the conversion, selectivity, and faradaic efficiency reach 99.7%, 99.5%, and 99.3%, respectively. Meanwhile, the electrode performance remains good after repeated reactions, with the conversion of benzyl alcohol and faradaic efficiency both being above 98.5%. The design of the electrode provides a new idea to broaden the range of organic reactions carried out by electrocatalysis. And it also helps to reduce the high overpotential caused by the original oxygen evolution reaction. [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]

In this study, it is proposed to develop new electrodes for high performance and flexible supercapacitors by doping sodium borate (Na2B4O5(OH)4·8H2O) (NaB) and zinc borate (Zn3B6O12·3.5H2O) (ZnB) to poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) for the first time. NaB and ZnB were doped to PEDOT:PSS in different ratios (0, 0.3, 0.6, 1.25 and 2.5 mg ml−1) and coated on glass substrates by a spin coating method, which is a simple and low cost deposition technically. Studies were carried out to determine the structural, electrical, optical and morphological properties of the thin films produced. Electrochemical properties were determined by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) tests. The 2.5 mg ml−1 NaB doped PEDOT:PPS/GCE exhibited 10 times higher capacitance than the undoped PEDOT:PSS electrode material (1.0 V potential range, 0.1 M NaCl electrolyte). This study proposes a new electrode material produced at low cost in one-step for supercapacitor applications with improved electrochemical performance. [ABSTRACT FROM AUTHOR]

Nanomaterials synergy in a binary system offers a great opportunity for the development of high-performance electrode material for Lithium-ion batteries (LiBs). So far SnS/Ni3S4 binary sulfides are scarcely investigated as an anode for LIBs. In this work, to intrinsically enhance the kinetics of SnS, SnS/Ni3S4 (SN-x) binary sulfides were synthesized by introducing nickel sulfide with different stoichiometric ratios (0.5, 1, 2, and 3). The developed electrode (SN-2) delivers an initial discharge capacity of 2567 mA h g−1 and a high reversible capacity of 360 mA h g−1 at a current rate of 300 mA g−1 after 180 cycles with a Coulombic efficiency of over 97%. The electrochemical impedance spectroscopy (EIS) and density functional theory (DFT) confirm the improved kinetics of the SN-2 electrode as compared to other electrodes. The significantly enhanced performance of the SN-2 electrode can be attributed to the addition of an optimized amount of Ni3S4, synergistic effects between SnS and Ni3S4, generation of more active sites and structural integrity. This work suggests that the prepared SnS/Ni3S4 binary sulfides exhibit great promise for the development of efficient energy storage devices. [ABSTRACT FROM AUTHOR]

In this work, a new poly(2,20:50,200-terthiophene) derivative with an electron-rich pendant group was designed using a side-chain engineering approach to prepare high performance redox-active electrode materials for electrochemical energy storage applications. The poly(2-((2-(4-(([2,20:50,200-terthiophen]-30- ylmethylene)amino)phenoxy)ethyl)thio)ethanol) (PKAAN) was electrodeposited via a constant potential electrolysis method on stainless steel current collector substrates without any template material or polymeric binder and directly used as a redox-active electrode material. The non-substituted poly(2,20:50,200-terthiophene) (PTTh) conducting polymer derivative was also prepared to assess the effect of the side chain substituent on the morphological, mechanical and charge storage performance of the PKAAN redox-active electrode material. The morphological features of the PKAAN- and PTTh-based conducting polymer films were monitored by scanning electron microscopy (SEM). Cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques were employed to examine the electrochemical performances of the redox-active electrodes in both 3-electrode and 2-electrode cell configurations. The SEM evaluations revealed that the PKAAN electroactive film possesses a unique 3D and porous morphology offering more effective diffusion pathways for ion transportation during the charge/discharge cycles compared to the PTTh polymeric network. The PKAAN redox-active electrode material achieved superior electrochemical charge storage performance with a gravimetric specific capacitance of 369 F g-1 at a constant current density of 2.5 mA cm-2 at a potential of 1.85 V in single electrode measurements. Furthermore, the PKAAN electrode exhibited outstanding cycling durability and mechanical stability upon long-term cycling. The PKAAN redoxactive electrode material retained 93% of its initial capacitance at the end of 12500 repeating charge/discharge cycles. The solid-state symmetrical supercapacitor device assembled using PKAAN electrodes delivered a specific capacitance of 205 F g-1, an energy density of 77.5 W h kg-1 and a power density of 750 W kg-1 in an operating voltage window of 1.85 V. In addition to its energy storage behavior, the supercapacitor device demonstrated excellent cycling stability with a capacitance decrease of only 7.5% after 12500 repeated cycles. The results reveal that the side-chain engineering strategy can be used as a facile and effective way to design conducting polymer-based electrode materials with desired morphological, mechanical and electrochemical features for high-performance energy storage applications. [ABSTRACT FROM AUTHOR]

Biomass carbon materials, which are environmentally friendly, have received significant attention and rapidly developed in the field of electrochemical devices. In this study, rice husk carbon (RHC) was prepared using calcination and activation methods, and a layer of nickel–cobalt double hydroxide (NiCo-LDH) was grown on the surface of RHC using a hydrothermal method, resulting in the formation of the NiCo-LDH@RHC composite. The open nanoflower structure and the synergistic effect between RHC and NiCo-LDH increased the conductivity and stability of the electrode material, as well as its specific capacitance. The NiCo-LDH@RHC electrode delivered a high specific capacity of 8542.5 mF cm−2 at a current density of 2 mA cm−2 with a good cycling stability of 80.45% across 5000 cycles. Furthermore, a high-performance all-solid-state asymmetric supercapacitor (ASC) was assembled using Fe2O3/CC as the anode material and NiCo-LDH@RHC as the cathode material. It displayed a high energy density of 61.44 μW h cm−2 at a power density of 3.99 mW cm−2 and an excellent cycle retention rate of 86.54% after 10 000 cycles. This research demonstrates that NiCo-LDH@RHC is an environmentally friendly and high performance electrode material with great development potential. [ABSTRACT FROM AUTHOR]

Interparticle contact is crucial for high-performance all-solid-state lithium-ion batteries because it determines charge transfer path formation. However, sulfide electrolytes and Si react under compositing conditions, realizing good interparticle contact. Therefore, this study delves into the relationship between the interface reaction and battery performance for the Si-composite electrode. [ABSTRACT FROM AUTHOR]

As a promising continuous desalination technology, flow electrode capacitive deionization (FCDI) has received considerable attention. However, poor conductivity and dispersion of the traditional active carbon (AC) flow-electrode limit the properties of FCDI. In order to achieve excellent desalination performance, a flow electrode with good dispersion, low resistance, and high salt adsorption capacity is essential. In this study, nitrogen-doped porous carbon (NPC) was synthesized through one-step pyrolysis process of ethylenediamine tetraacetic acid tetrasodium (Na4EDTA). The prepared NPC material showed a high specific surface area (1168.4 m2 g−1), appropriate nitrogen and oxygen doping, excellent hydrophilicity and low resistance. At 1.2 V applied voltage, the desalting experiments showed that the FCDI system based on a NPC flow electrode exhibited a higher average salt removal rate of 0.0459 mg cm−2 min−1, and the salt adsorption capacity (148.93 mg g−1) based on the NPC flow electrode was about 2.3 times larger than that of AC. Furthermore, after continuous desalination cycling for long periods of time, the salt removal efficiency and average salt removal rate remained stable. The results of this study may be useful for the future exploration of high performance electrode materials for FCDI systems. [ABSTRACT FROM AUTHOR]

Energy storage devices (ESDs) need designing and development of high electrochemical performance and promising electrode materials. Transition-metal chalcogenides (TMCs) are being actively investigated as the electrode for electrochemical ESDs. Herein, we report the design, synthesis, and electrochemical properties of the MnSe electrode by a facile hydrothermal method. The as-synthesized MnSe electrode has a flower-like morphology with the planes growing perpendicular to its center. The results of electrochemical performance testing indicate that the pseudocapacitive nature of the MnSe electrode has a critical effect on those properties. The MnSe electrode exhibits a specific capacitance of 423.1 F g−1 at a current density of 1 A g−1 and better cyclic stability among 3000 cycles. The synthesis of MnSe electrodes opens up opportunities for the design of TMCs electrode materials and the development of supercapacitors. [ABSTRACT FROM AUTHOR]

The inherent properties, poor exposed active sites and the cumbersome manufacturing process have severely hindered metal–nitrogen–carbon structures in their applications in electric vehicles and stationary energy storage systems. Herein, we report a novel pyrolysis-induced gas diffusion strategy to synthesize nitrogen-rich hierarchical porous carbon nanoscrolls with highly dispersed single-atom Co sites (Co–N–C) as electrode materials for the electrocatalytic oxygen reduction and lithium-ion batteries (LIBs). In this method, Co doped g-C3N4 (Co–CN) is not only used to anchor Co single-atoms to increase the intrinsic active sites, but also served as a sacrificial template to adjust the N content and increase the electrochemically active surface area of the carbon material. Furthermore, self-curling and in situ produced NH3 from Co–CN diffusion effects tune the structural characteristics of the mesoporous carbon nanoscrolls to fully expose the active center and facilitate rapid ion transport. As a result, these carbon nanoscrolls display an enhanced oxygen reduction reaction (ORR) with a half-wave potential of 0.87 V vs. RHE, better than that of the state-of-the-art Pt/C catalyst, and a superior electrochemical performance as an anode material for LIBs, showing a specific capacity of 589.1 mA h g−1 at 2.0 A g−1 even after 900 cycles. Such a finding provides a facile pyrolysis-induced gas diffusion strategy for synthesizing high performance electrode materials. [ABSTRACT FROM AUTHOR]

In this article, we report an effective synthesis of a cobalt-benzimidazole metal organic framework (Co-Bim MOF), which belongs to the Zeolitic imidazolate framework-9 (ZIF-9) family, and a cobalt- benzimidazole MOF@reduced graphene oxide (Co-Bim@rGO) composite through hydrothermal treatment for supercapacitor application. The structural and morphological features of the Co-Bim MOF and Co-Bim@rGO composite were confirmed by using various physicochemical techniques such as FT-IR, Raman, XRD, SEM, TEM, BET and XPS analysis. The SEM and BET analysis of the Co-Bim@rGO composite shows a layer-like structure with abundant pores and a large surface area (543 m² g-1). The supercapacitive performance of the prepared electrodes was investigated using CV (cyclic voltammetry), GCD (Galvanostatic Charge-Discharge) and electrochemical impedance spectroscopy (EIS) analyses in aq. 1 M KOH. The as-fabricated Co-Bim@rGO composite showed a specific capacity of 1488 C g-1 at 1 A g-1 and maintained 96% of its initial capacitance after 8000 GCD cycles at 4 A g-1. The superior capacity performance of the Co-Bim@rGO composite is mainly ascribed to its mesoporous nature with an improved surface area, multiple redox sites and synergistic effect between the Co-Bim MOF and rGO moiety. The constructed Co-Bim@rGO//AC device showed an energy density of 90.55 W h kg-1 at a power density of 2396.28 W kg-1, and the device showed a cyclic stability of 88% even after 4000 GCD cycles at 3 A g-1. Further, biocompatibility analysis of the Co-Bim MOF and Co-Bim@rGO composite proved the non-toxic nature of the as-prepared electrode material. Thus, the effective energy storage ability of the Co-Bim@rGO composite confirms it as a potential candidate for supercapacitors in day-today applications. [ABSTRACT FROM AUTHOR]

The nanoscale Li2Mn0.8Ni0.2SiO4/MnO2 composite was successfully prepared via a two-step method. Firstly, by the preparation of MnO2 nanoparticles through an oxidation-reduction reaction; secondly, by synthesizing Li2Mn0.8Ni0.2SiO4 using an EDTA-assisted sol–gel method; finally, the two nanoparticles mixed together by hand milling to form the nanocomposite. The synthesized nanoparticles were characterized using several techniques. The nanocomposite presents a well-developed orthorhombic crystal structure with a Pmn21 space group, although there are small impurities of MnO and Li2SiO3. The BET surface area measurements indicate that all the prepared materials are mesoporous. The effect of nanoscale MnO2 on the electrochemical properties of the Li2Mn0.8Ni0.2SiO4 nanomaterials was evaluated. The composite (denoted as (LMNS/M2) exhibited a specific capacity of 962.4 C g−1 at the current density of 2 A g−1. Furthermore, a hybrid device using this composite as a cathode and commercial activated carbon (AC) as an anode was fabricated to examine the practical aspects of the novel electrode, which conducted a specific energy of 38.1 W h kg−1 at a specific power of 938.4 W kg−1. It preserved a capacity of 84% after 2000 cycles. Li2Mn0.8Ni0.2SiO4/MnO2 is a promising candidate for high-efficiency energy storage electrode materials for supercapacitor applications because of its superior performance and ease of preparation. The obtained results confirm the excellent electrochemical performance of the electrode as a promising electrode for energy storage applications. [ABSTRACT FROM AUTHOR]

This work explores the utilization of coal fly ash (FA) for supercapacitor (SC) applications. Subcritical water extraction (SWE), a pressurized hydrothermal process, under acidic conditions was used to prepare FA as a SC electrode material; this is essential to remove the undesired compounds from FA powder as well as to improve its electrical conductivity. The effect of acid concentration in SWE process on the SC performance of the FA electrode was investigated. Characterizations such as galvanostatic charge–discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were carried out to determine the electrochemical properties of samples. The FA electrode with 0.5 M acid pretreatment in SWE (FA-0.5) resulted in the best performance of the SC. The specific capacitance (Cs), energy density (Ed), and power density (Pd) of FA-0.5 as an electrode are calculated to be 620 F g−1, 22 W h kg−1, and 500 W kg−1 at 2 A g−1, respectively, in 3 M KOH alkaline solution. The energy storage capability might originate from the contained silicon dioxide and metal oxides in the FA-0.5 sample. The demonstration of a full cell supercapacitor was also performed by assembling FA-0.5 and activated carbon (AC) as the cathode and anode, respectively. Under a current density of 2 A g−1, the asymmetrical FA-0.5//AC cell exhibits an Ed of 99 W h kg−1 and Pd of 1600 W kg−1 in the PVA-KOH gel electrolyte. This work provides an alternative valorization process to convert solid waste of coal FA by a novel SWE technique to an advanced energy storage application. [ABSTRACT FROM AUTHOR]

Heterointerfaces not only provide more sites for lithium ion storage, but also reduce the damage of electrode active materials, which are conducive to boosting the capacity and cycle stability of the electrode. This paper demonstrates for the first time that nanofibers with a NiO/Co3O4/NiCo2O4 heterostructure can be prepared by adjusting the annealing temperature. These heterostructured nanofibers are derived from as-spun Ni/Co nanofibers prepared by using electrospinning through thermal annealing at 500–800 °C. The phase formation and decomposition of spinel NiCo2O4 occur during heat treatment, and the composition is dependent on the annealing temperature. The electrochemical properties of the electrodes are correlated with the phase composition, particle size and morphology of the nanofibers. The nanofiber electrode annealed at 650 °C exhibits optimal electrochemical performances. Its specific capacity continues to increase at the initial stage of charge–discharge, and the activation cycle reached 61 cycles. The electrode has the largest boost value of 187.6 mA h g−1 (boost ratio, 21.08%), and its specific capacity reaches 1081.4 mA h g−1. The charge storage mechanism is analyzed by using cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic intermittent titration technique measurements. The contribution of electrode pseudo capacitance increases from 66.27% to 73.09% as the scan rate increases from 0.2 to 1.0 mV s−1, revealing that both the diffusion- and capacitive-controlled processes contributed. This is a facile and low-cost strategy to prepare high performance electrode materials for lithium-ion batteries, and stimulates the further development of phase-transition-induced synthesis of nanofibrous heterostructures. [ABSTRACT FROM AUTHOR]

Electro-conducting polypyrrole (PPy) coated H2N-SiO2/Ni nanocomposite particles are prepared by a three-step process. The objective is to analyze the influence of porous functional SiO2 support on the electrochemical performance of the prepared H2N-SiO2/Ni/PPy nanocomposite particles. H2N-SiO2 support is first prepared by a modified sol–gel method and then co-ordinated with Ni nanoparticles via an amine functionality. Finally, H2N-SiO2/Ni/PPy nanocomposite particles are prepared by in situ chemical oxidative polymerization of pyrrole using citric acid as a dopant. Fourier Transform IR (FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the formation of co-ordinated Ni/Ni2+ nanoparticles and a PPy layer with almost a core–shell type morphology. The mesoporous surface structure of H2N-SiO2 core-particles is confirmed from the morphological study and the specific surface area gradually decreased from 496 m2 g−1 to 59 m2 g−1 following subsequent surface modification with Ni nanoparticles and the PPy layer. The ultimate nanocomposite particles had paramagnetic properties and the magnetization value is 4.8 emu g−1. Comparative electrochemical performance between electrodes made from the respective PPy, Ni/PPy and H2N-SiO2/Ni/PPy showed the highest specific capacitance value (982.6 F g−1 from cyclic voltammetry curves) for the H2N-SiO2/Ni/PPy nanocomposite. The H2N-SiO2/Ni/PPy nanocomposite electrode is fairly stable during cycling measurement. The results indicated that the use of mesoporous functional SiO2 support remarkably improved the mechanical stability and capacitive performance of the H2N-SiO2/Ni/PPy nanocomposite electrode, suitable for application in energy storage devices. [ABSTRACT FROM AUTHOR]

Tin oxides are the most promising anode materials for sodium-ion batteries (SIBs) owing to their abundance and their multi-electron reactions, which ultimately provide a high theoretical capacity. However, the huge volume expansion and consequent stability issues of tin and tin oxide anodes have relentlessly hindered their application in Na-ion batteries. To overcome these drawbacks, we present a facile strategy to prepare a non-metal-doped Sn3O4 anode by facile hydrothermal route and the investigation of its sodium-ion storage performance. B-F@Sn3O4 exhibits a triclinic structure with nanoflake morphology, length of 40–100 nm, and thickness of 10–15 nm. When applied as the anode material for SIBs, the resultant material exhibits excellent sodium-ion storage abilities in terms of cycling stability and high rate capability. In SIBs, the Sn3O4 anode capacity was observed to be 732.8 mA h g−1 at a current density of 50 mA g−1, and good cycling performance at 200 mA g−1 with a capacity retention of 77.5% after 120 cycles. Furthermore, the diffusion coefficients of the sodium ions calculated based on EIS measurements were observed to be in the range of 10−13 to 10−11 cm2 s−1, which reveals the admirable diffusion mobility of Na atoms in the Sn3O4 nanoflakes. Moreover, a coin-type sodium-ion full cell consisting of the B-F@Sn3O4 anode and a Na3V2(PO4)3 cathode exhibited a capacity of 81.2 mA h g−1 at C/20. This study demonstrates that the Sn3O4 is a promising anode material for SIBs. Thus, the B-F-doped Sn3O4 material assembled by interconnected nanoflakes is capable of providing fast carrier transmission dynamics and outstanding structural integrity, suggesting the feasibility of the current framework for sodium-ion storage. [ABSTRACT FROM AUTHOR]

Flower-like nanosheets of pure molybdenum disulfide (MoS2) and Fe-doped MoS2 (FM) with 2, 4 and 8% atomic-doped iron of FM-2, FM-4 and FM-8, respectively, were successfully synthesized using the hydrothermal method. The effect of iron doping on the MoS2 morphology, composition, and supercapacitor behavior are systematically investigated. In the Fe-doped MoS2 samples, iron atoms replaced the molybdenum atoms in the MoS2 structure through the hydrothermal process. Cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) measurements were conducted on a three-electrode system to evaluate the electrochemical performance of the electrodes. The specific capacitance of the FM-2 electrode was 240 F g−1 at a 10 mV s−1 CV scan rate, which was higher than that of the pure MoS2 and the other two Fe-doped MoS2 electrodes. Furthermore, EIS tests exhibited that doping iron in the MoS2 structure contributes to a rapid decline in charge transfer resistance and, therefore, a higher probability of energy storage. The results revealed that the synthesized Fe-doped MoS2 samples are potential electrode materials for future energy storage devices. [ABSTRACT FROM AUTHOR]

BiVO4/NiFe was synthesized on Ni foam using a simple hydrothermal method and successive ion layer absorption and reaction (SILAR) method. The BiVO4/NiFe electrode was used as a photoanode for photoelectrocatalytic (PEC) degradation of tetracycline (TC) in wastewater with simultaneous cathodic hydrogen production. The photoelectrochemical and catalytic properties of the prepared electrodes were studied using a series of characterization and measurements. The unique Z-scheme BiVO4/NiFe heterojunction has a synergistic effect, which can significantly improve the absorption of visible light, accelerate the charge transfer and consequently inhibit the complexation of e−–h+ pairs. These characteristics of the heterojunction contribute to the prominent PEC performance of the BiVO4/NiFe electrode. The trapping experiment showed that holes (h+) are the main active substances in the degradation process, and the electrode has good cyclic stability that the degradation efficiency had not decayed significantly after five repeated experiments. In addition, the BiVO4/NiFe photoanode displayed favorable degradation and cathodic hydrogen evolution efficiency simultaneously in the real sunlight conditions. This study provides a basis for the design of highly practical photoelectric electrodes and expands the application of PEC technology. [ABSTRACT FROM AUTHOR]

This paper reported an easy synthesis of MnCo2S4 (MCS) nanosheets using a one-pot solvothermal method for high performance supercapacitor electrode material applications. The obtained ultrathin MCS nanosheets with a thickness of approximately 10 nm are coated on a graphite paper substrate without a binder using the 3D printing technique to form supercapacitor electrodes. The electrochemical performance of the MCS electrode was studied by CV, GCD, EIS measurements in a 6 M KOH electrolyte using a three electrode system. As a result, the MCS electrode material exhibits a higher specific capacity of 2203.6 F g−1 at a current density of 3 A g−1 along with an excellent cycling stability of 93% after 5000 charge–discharge cycles. Furthermore, the symmetric supercapacitor is fabricated using a two-electrode system with synthesized MCS nanosheets and exhibits an outstanding energy density and power density of 96 W h kg−1 and 1857 W kg−1, respectively. These results demonstrate the potential of the MCS nanosheets as an efficient electrode material for next generation supercapacitors. [ABSTRACT FROM AUTHOR]

An electrochemical sensing electrode based on titania (anatase) and silica nanospheres (TiO2@SiO2 NSs) loaded on a pencil graphite electrode (TiO2@SiO2NSs/PGE) was fabricated and scrutinized for L-ascorbic acid detection. The PGE surface was designed by coating the nanospheres using the drop casting method. NSs and modified electrodes were investigated structurally, optically and morphologically using various characterization techniques. An electrochemical study was performed via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA). Further, the designed electrode performance was optimized by varying pH, potential and scan rates. The TiO2@SiO2NS/PGE-modified electrode showed a high sensitivity of 2696.9 μA mM−1 cm−2 and a lower detection limit for ascorbic acid. The modified electrode also revealed a linear range of 50–2500 μM with a regression coefficient of R2 = 0.9932. Additionally, the electrode exhibited high stability and good anti-interference capability. Similarly, the modified electrode performed well in real samples for ascorbic acid detection. Furthermore, TiO2@SiO2 NSs performed very effectively against harmful microbes including Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus and Shigella flexneri bacteria with good inhibition. [ABSTRACT FROM AUTHOR]

The preparation of an environmentally benign, inexpensive supercapacitor electrode material from waste biomass, achieving useful carbon electrode production, is challenging. The present work aims to find a process for recycling spent mushroom compost into a useful supercapacitor electrode material. Highsurface- area activated carbon derived from spent mushroom compost (SMC) is used as a catalyst electrode in a solid-state electrochemical double-layer capacitor (SSEDLC). The SMC is thermally activated at three different temperatures (SMC-700, SMC-800, and SMC-900) to achieve the optimal carbon content and activation temperature for improving electrode performance based on the surface area and pore structure. The SMC-derived nanostructured carbon exhibited a high specific surface area of 690 m² g-1 in the case of SMC-800 upon activation, which strongly influences the specific and areal capacitance of the fabricated SSEDLC. Interestingly, the use of the prepared PVA/H2SO4 gel electrolyte showed a promising trend, with considerable capacitance retention of up to 90% over 3000 cycles obtained with the material optimized at 800 1C (SMC-800). [ABSTRACT FROM AUTHOR]

Nanomaterial synergy in a hybrid system offers an unprecedented opportunity for the development of high-performance energy storage devices. In this work, to intrinsically boost the lithium storage properties of layered structure V2O5, hybrid systems involving V2O5/MWCNTs are synthesized and investigated as cathode materials for lithium-ion batteries. It is found that the V2O5/MWCNT electrode demonstrates a higher initial discharge capacity of 329 mA h g−1 with a coulombic efficiency of 97% at 0.1C between 1.5 V and 4.2 V versus Li/Li+. The developed electrode delivers a reversible capacity of 217 mA h g−1 at 0.1C after 100 cycles and 106 mA h g−1 at 1C after 500 cycles with a capacity retention rate of 84.7% and 80.9% respectively. In addition, electrochemical impedance spectroscopy (EIS) and density functional theory (DFT) confirm the enhanced kinetics of the V2O5/MWCNT electrode. The improved and efficient performance of the electrode is due to the synergy between V2O5 and MWCNTs, which facilitates a convenient path for fast Li+ ion diffusion and reduces the strain generated during the charge/discharge process. This work suggests that the reported V2O5/MWCNT hybrid system can be utilized as a cathode for the construction of LIBs with high-rate capability and long cycle life. [ABSTRACT FROM AUTHOR]

The high-rate performance of Ga2O3-based electrode has been seriously restricted by its modest reaction kinetics caused by the particular challenge of morphology regulation. Herein, Ga2O3–Li3VO4/N-doped C nanofibers (G–LVO/NC NFs) were successfully designed and firstly prepared via a concise electrospinning approach. The as-prepared G–LVO/NC NFs exhibit self-adaptive reaction kinetics owing to the synergistic effect among Ga2O3, Li3VO4, and N-doped C, resulting in superb high-rate Li-ion storage. After repeated rate-performance testing (4 periods) from 0.2 to 10.0 A g−1 over 380 cycles, a high reversible capacity of 968.8 mA h g−1 could be restored when reverting the current back to 0.2 A g−1. When cycling at various high charge/discharge currents of 2.0/4.0, 4.0/6.0, 6.0/8.0, and 8.0/10.0 A g−1, the G–LVO/NC NFs also deliver outstanding cyclability and high charge/discharge capacity of 606.5/608.6, 457.6/457.2, 435.6/435.8, and 317.1/317.9 mA h g−1 after 2000 cycles, respectively, demonstrating great potential toward high power density application. [ABSTRACT FROM AUTHOR]

Herein, we have prepared a new nanocomposite Bi2S3/Co3O4/rGO/Ni foam substrate electrode through hydrothermal synthesis and an annealing process. SEM clearly shows that the Bi2S3/rGO/Ni foam substrate and Co3O4/rGO/Ni foam substrate prepared under the experimental conditions are cuboid-shaped and flower-shaped, respectively. However, the shape of Bi2S3/Co3O4/rGO/Ni foam is a perfect combination of the above two. We call this cuboid full of petals a flower-rod-like shape. The BET test found that the specific surface area of this unique morphology is as high as 152.7 cm2 g−1, which is beneficial towards charge transfer and improves the overall electrochemical reaction performance of the electrode. In addition, electrochemical performance tests displayed that the Bi2S3/Co3O4/rGO/Ni foam electrode had a high specific capacitance of 2214.3 F g−1 at 1 A g−1. The highest energy density of the Bi2S3/Co3O4/rGO/Ni foam//activated carbon asymmetric supercapacitor is 133.4 W h kg−1 (the corresponding power density is 800.1 W kg−1), and the highest power density is 8568.2 W kg−1 (the corresponding energy density is 70.5 W h kg−1). Additionally, under the condition of 10 A g−1 current density, the capacitance retention rate is still extremely high: 99.4% after 10 000 continuous charge and discharge tests. In practical application, two Bi2S3/Co3O4/rGO/Ni foam//activated carbon asymmetric supercapacitors in series can make a 2.5 V bulb maintain a high brightness for 1 minute. [ABSTRACT FROM AUTHOR]

Designing flexible supercapacitors (FSCs) as energy storage devices for portable/wearable electronic products using the earth-abundant, renewable and environmentally friendly natural biomass has the prospect of building a green, sustainable society. Here, we report a new type of three-dimensional graphene hydrogel with lignin-based nitrogen-doped carbon dots as a decorative material. The nitrogen doped carbon dots are anchored in a graphene sheet through π–π bonds and electrostatic interactions, forming a stable three-dimensional network structure, which comprehensively improves the electrochemical performance of the electrode material. As an electrode, the specific capacitance reaches 387 F g−1 at 1 A g−1, and the rate performance reaches 75.7% when the current density increases to 7 A g−1. In addition, an all-lignin-based supercapacitor assembled with a lignin hydrogel as the electrolyte has superior cycle stability (cycle life after 5000 cycles is 92.3%) and rate performance. When the power density is 243 W kg−1, the energy density is 25.6 W h kg−1; moreover, the FSC has excellent electrochemical stability even at different bending angles. This all-lignin-based FSC with excellent electrochemical performance and flexibility opens up a new path for the application of lignin in flexible energy storage devices. [ABSTRACT FROM AUTHOR]

Two cobalt metal–organic frameworks (Co-MOFs), [Ch]2[Co3(BDC)3Cl2] (1) and [Ch]2[Co3(BDC)4]·2DMU (2) (Ch+ = choline cation; H2BDC = terephthalic acid; DMU = 1,3-dimethylurea), were prepared through ionothermal reactions with deep eutectic solvents (DESs) of ChCl and DMU as the reaction media. The 1/GCE electrode with better current response was selected as the electrocatalyst. The detection performance of the 1/GCE electrode towards glucose is excellent with a wide linear range of 10–1200 μmol L−1, a detection limit of 3.2 μmol L−1 (S/N = 3), and a rapid response less than 3 s in 0.01 mol L−1 NaOH. 1 also exhibits high anti-interference with the existence of D -Man, D -Fru, DL -AA, and BA, long-term stability of 15 days and reproducibility for glucose detection. 1 was utilized to detect glucose in human serum and orange juice. The found glucose concentrations are very close to the added glucose concentrations in the selected situations with low RSD and high recoveries. This demonstrates that as a non-enzymatic glucose sensor, 1/GCE can detect glucose with high accuracy and reliability in different environments. [ABSTRACT FROM AUTHOR]

Biochar (BC) is a kind of carbon-rich, renewable and low-cost material, which can be prepared from various organic materials. In this work, biochar was used as the electrode material to prepare a novel rolled electrode as a cathode for the Electeo-Fenton (EF) system. The results showed that a quite high generation of H2O2 (609 mg L−1) could be obtained on the optimum-mixed cathode of carbon black and biochar (BC–CB-(1 : 1)) at a low electric energy consumption (EEC) (32.8 kW h kg−1). Furthermore, the operating parameters such as airflow rate, pH, and current density, affecting the H2O2 electro-generation, were investigated and optimized. The optimum conditions for H2O2 generation were air flow rate 0.6 L min−1, current density 32 mA cm−2 and initial pH 7.0. The achieved removal rate of tetracycline was 95.3% within 10 min, and the TOC mineralization could reach 91% on the optimum mixed cathode, which was much higher than that of raw biochar cathode. In terms of stability, the mixed cathode remained stable after 10 cycles. The optimized design considerably improved the electrochemical performances of the electrode, which offer a cost-effective strategy for organic pollutant removal by the EF process. [ABSTRACT FROM AUTHOR]

Herein, MnS was prepared in situ with Ni3S2 directly on nickel foam to obtain a novel binder-free highly conductive electrode with a superb echinocactus-like morphology. The novel electrode gives ultra-high results when examined as an electrode for supercapacitor applications, such as an areal capacity of 796.7 mA h cm−2 equivalent to an areal capacitance of 2390 F cm−2 at a current density of 3 mA cm−2, in addition to low resistance and a remarkable potential window. Furthermore, a hybrid device using this electrode as a positive electrode and commercial activated carbon as a negative electrode was fabricated to examine the practical aspects of the novel electrode, which conducted a specific energy of 77.5 W h kg−1 at a specific power of 18 000 W kg−1. Interestingly, it preserved a specific energy of 33.3 W h kg−1 at a specific power of 50 000 W kg−1 and a satisfactory capacity retention of 80% after 2000 cycles with a Coulombic efficiency reaching 99%. These results confirm the electrode's superior electrochemical performance as a promising electrode for energy storage applications. [ABSTRACT FROM AUTHOR]

We report a novel, facile and versatile electrophoretic deposition approach to prepare a three-dimensional rGO@NF structural electrode as a binder-free structural supercapacitor electrode in the field of building energy storage applications. Nickel foam (NF) was used as the carrier of electrode active material and the electrophoretic deposition of GO on NF was carried out using a signal generator. Typical SEM photographs indicate that a large amount of highly conductive graphene was successfully anchored on a porous nickel foam framework by electrophoretic deposition and a thermal reduction process at high temperature, which provides enough channels for ion storage and migration. The resulting 3D rGO@NF structural electrode exhibited good double-layer behavior due to its high conductivity, porous structure and sufficient deposition mass of graphene. In order to investigate the effects of high temperature thermal reduction time, duty cycle, voltage and frequency on the electrochemical performance of the structural electrode in detail, chemical and physical analyses and electrochemical tests of the rGO@NF structural electrode were carried out. The electrodeposition method shows good potential in the preparation of various types of three-dimensional carbon-based structural electrodes used in the field of building energy storage applications. [ABSTRACT FROM AUTHOR]

Electrocatalytic water splitting reaction utilizing non-renewable energy resources significantly leads to a sustainable energy infrastructure. Highly efficient bifunctional catalysts for oxygen reduction and oxygen evolution reactions (ORR/OER) are essential for the replacement of platinum, ruthenium and iridium metals. We used four different silica templates to create excellent mesoporous cobalt oxide (Co3O4) electrocatalysts in crystalline form. Various advanced techniques confirm the spinel structure composed of both Co3+ and Co2+ sites, which lead to an enhanced surface area, mesoporosity, and a rod morphology with a cubic-like network structure. Among these replicas, the Mobil composition of matter (MCM)-48-derived Co3O4 (Co3O4-M8) material demonstrates remarkable OER activity with an observed potential of 1.76 V, a Tafel slope of 107 mV dec−1 and a lower charge transfer resistance. Such a high performance is observed due to assistance of the Co3+ to Co4+ transition during the oxygen evolution reaction. The ORR was more active on the Korea advanced institute of science and technology (KIT)-6-derived Co3O4 (Co3O4-K6) material, which displayed a more positive onset potential of 0.85 V, a half-wave potential of 0.56 V and a better current density in alkaline medium. In addition, we found that the stabilization of Co2+ active sites in the Co3O4-K6 material is the reason for the enhanced oxygen reduction reaction. The observed bifunctional activity (ΔE = EOER@10 mA cm−2 − ORR@E1/2) for the Co3O4-K6 catalyst is 1.22 V, which shows significant performance among all the catalysts prepared in this work. Such an earth-abundant mesoporous Co3O4 catalyst obtained via an environmentally benign process is anticipated to revolutionize electrochemical energy conversion and storage devices. [ABSTRACT FROM AUTHOR]

The preparation of a stable, efficient, inexpensive and high capacitance electrode material for supercapacitors is posing great challenges for researchers. In this report, we demonstrate the synthesis of a stable, conductive and highly active graphene nanoplatelet (GNPL) enriched polythiophene via in situ chemical polymerization for supercapacitor applications. The characteristic X-ray diffraction patterns proved the formation of the as-prepared nanomaterials. The morphological studies revealed that PTh NPs are successfully anchored onto the surface of the GNPLs during polymerization. The elemental mapping revealed the presence of carbon, oxygen, and sulfur in the GNPLs/PTh. The cyclic voltammetry (CV) measurements showed that the 50% GNPLs/PTh electrode exhibited a maximum specific capacitance of 960.71 F g−1 at a scan rate of 10 mv s−1. The gravimetric capacitance of the designed electrodes reached 673 F g−1 at a current density of 0.25 A g−1, corresponding to an energy density of 2.25 W h kg−1 and a power density of 23.55 W kg−1. The EIS results of the 50% GNPLs/PTh showed a minimum resistance of charge transfer (Rct) and equivalent series resistance, signifying the superior charge propagation behavior at the interfacial region. The cycling stability investigation highlighted that the 50% GNPLs/PTh based supercapacitor can retain 84.9% of the initial capacitance after 1500 successive CV cycles, suggesting excellent cycling stability of the material. These findings conclude the high potential of the newly synthesized GNPLs/PTh as an electrode material for charge storage devices. [ABSTRACT FROM AUTHOR]

MOFs (metal–organic frameworks) are ideal precursors for constructing hierarchical structures utilized for energy storage, gas separation/capture, and waste adsorption. ZIF-67, a widely used MOF, can be converted to a Ni–Co-LDH battery-type electrode in Ni(NO3)2 ethanol solution for supercapacitor application. Herein, ZIF-67 was treated with Ni(NO3)2 ethanol solution at different soaking time periods. All products exhibited hierarchically porous hollow nanocages and were characterized to illustrate the conversion process and the effects of ZIF-residuals on the electrode performance. The results indicated that the ZIF residuals drastically influenced the ionic diffusion efficiency of electrolyte ions within the electrode and faradaic resistance between the electrolyte/electrode interfaces. The optimized Ni–Co-LDH-4.5 h electrode presented a remarkable charge storage behavior with a specific capacity of 732 C g−1 at the current density of 1 A g−1 and maintained its 68.3% capacitance (500 C g−1) at 25 A g−1. The fabricated all-solid state asymmetric supercapacitor presented a remarkable energy density of 45.33 W h kg−1 at the power density of 395.13 W kg−1. The cycling test indicated that 78.55% of the initial capacitance was retained after 8000 cycles, illustrating the remarkable long-life performance. [ABSTRACT FROM AUTHOR]

The copper current collector is an essential part of lithium-ion batteries (LIBs) that can greatly affect safety, stability, and energy density and it is thus of great importance to develop a strategy for improving copper (Cu) current collectors. Here, two kinds of conductive polymer (poly(3,4-ethylenedioxythiophene) (PEDOT) or polyaniline (PANi))-modified Cu foils were created through a facile anodic electrochemical polymerization method. These modified Cu foils improved the conductivity, bonding strength with electrode materials, and corrosion resistance to electrolyte, which led to superior LIB storage performance with Cu-graphite electrodes. The results showed that initial discharging capacities of Cu-graphite/Li half cells with PEDOT and PANi modification were as high as 353.9 and 332.8 mA h g−1, respectively, which were much higher than those of pristine Cu-graphite/Li half-cells (312.2 mA h g−1). After 200 cycles at 0.5 C, the discharging capacities remained at 323.27 and 279.62 mA h g−1, with capacity retention rates of 95.64 and 87.43%, respectively, which were also much higher than those of pristine Cu-graphite/Li half-cells (189.81 mA h g−1 and 67.41% retention after 200 cycles). These results indicated that Cu current collectors modified by a conductive polymer could provide a feasible approach for improving the capacity and long-life of LIBs. [ABSTRACT FROM AUTHOR]

A ZnMoO4 porous nanosheet with oxygen vacancies (ZnMoO4-OV) was synthesized by hydrothermal synthesis and the hydrogenation reduction method. The ZnMoO4-OV porous nanosheet delivers a higher specific surface area together with a more diverse pore size distribution compared to the ZnMoO4 nanosheet. The density functional theory calculation results exhibit that ZnMoO4-OV has lower energy band gap (3.019 eV) than ZnMoO4 (1.92 eV). The electronic density of states plots reveal that ZnMoO4-OV possesses higher electron state distribution at the Fermi energy level than ZnMoO4. ZnMoO4-OV porous sheet achieves higher specific capacitance (1673 g−1) than ZnMoO4 (797 F g−1) at 2 mA cm−2. It also achieves superior capacitance retention rate (82.9%) to ZnMoO4 (48.6%) with the current density increasing from 2 to 20 mA cm−2. The introduction of oxygen vacancies can increase the carrier density, accelerate the electron transfer, promote the electrical conductivity, and accordingly strengthen the redox reactivity of ZnMoO4-OV. An asymmetric supercapacitor is also constructed by using ZnMoO4-OV as the positive electrode and activated carbon as the negative electrode. It achieves a high energy density of 60.1 W h kg−1 at a power density of 800 W kg−1, together with a good cycle life. Both experimental measurements and theorical calculations are applied to prove the promotive role of oxygen vacancies to achieve the supercapacitive performance of ZnMoO4-OV. [ABSTRACT FROM AUTHOR]

Through one-step reaction, a robust hypercrosslinked pyrene-based porous organic polymer (HcPPy) with a high BET surface area was effectively achieved from pyrene. HcPPy was demonstrated as an excellent electrode material. When explored as an anode material for lithium ion batteries, HcPPy exhibited a high capacity even at high current densities (up to 683 mA h g−1 at 1000 mA g−1). When used as a cathode material, HcPPy exhibited good rate and cycling stability with a capacity of 110 mA h g−1 at 100 mA g−1 over 200 cycles. [ABSTRACT FROM AUTHOR]

A flexible film electrode composed of sodium carboxymethyl cellulose (CMC), polypyrrole (PPy) and reduced graphene oxide (RGO) was designed by in situ polymerization and vacuum filtration. The obtained film displayed CMC–PPy nanospheres wrapped in an RGO framework, resulting in a free-standing and highly flexible supercapacitor electrode. The incorporation of hydrophilic CMC into the film enhanced the diffusion paths of electrolyte ions and prevented the volume deformation of PPy during the long-term charging/discharging. Furthermore, PPy provided a large pseudocapacitance and RGO endowed the film electrode with prominent flexibility. The remarkable interaction between CMC, PPy and RGO achieved a synergistic effect on the structural stability and electrochemical performance of the film electrode. When the mass ratio of CMC–PPy to RGO was 1 : 1, the highest specific capacitance of the sodium carboxymethyl cellulose–polypyrrol@reduced graphene oxide (S-CPR1 : 1) was 489 mF cm−2 (191 F g−1) with a mass of 2.56 mg cm−2 at a current density of 0.5 mA cm−2. And the area specific capacitance of the S-CPR1 : 1 electrode could remain as 101.6% of the original value after 1000 charge/discharge cycles, which was higher than the polypyrrol@reduced graphene oxide (S-PR) electrode (72.4%) prepared under the same conditions. Besides, the S-CPR1 : 1 electrode exhibited remarkable flexibility with 95.6% capacity retention after 500 fold cycles. These above results indicated that the S-CPR1 : 1 film electrode provided a simple way of developing free-standing and flexible electrode materials for next-generation electrochemical electrodes. [ABSTRACT FROM AUTHOR]

In recent years, in order to meet the increasing demand for lithium-ion batteries (LIBs) with high energy density, various positive electrode materials have been developed. The higher the Ni content is, the better the performance of the alloy electrode is and the larger its capacity is. Increasing the charging voltage can improve the capacity of the electrode material and the voltage platform performance. However, as the charging voltage increases, the stability of the interface between the positive electrode material and the electrolyte will decrease, causing an increase in side reactions, which would seriously affect the cycle performance of LIBs. Herein, dimethyl trimethylsilyl phosphite (DMTMSP) was used as an efficient multifunctional electrolyte additive for high-voltage lithium cobalt oxide (LiCoO2). Protective films would be formed on the positive electrode and the negative electrode surface by electrochemical redox reactions, and the stability of the positive electrode material–electrolyte interface was highly improved whereas the impedance was decreased. On addition of 0.5 wt% of DMTMSP into the electrolyte, the battery exhibited outstanding low-temperature discharge and cycling performances (capacity retention remained at 82.7% at −20 °C with a rate of 0.3C and at 75% at elevated temperature even after 480 cycles). [ABSTRACT FROM AUTHOR]

Three-dimensional core–shell-structured TiO2@PPy/rGO nanocomposites were successfully constructed from TiO2@PPy nanospheres and graphene oxide via a polymerization method. First, TiO2 nanoparticles were uniformly coated with polypyrrole (PPy), forming core–shell TiO2@PPy nanospheres. The as-prepared TiO2@PPy nanospheres further self-assembled with graphene oxide (GO), resulting in the formation of three-dimensional ternary TiO2@PPy/rGO nanocomposites. Due to the strong interactions between TiO2@PPy and reduced graphene oxide (rGO), the three-dimensional TiO2@PPy/rGO electrode exhibited larger specific capacitance, lower charge transfer resistance, and more stable cycling performance compared to the TiO2@PPy nanospheres. More importantly, the existence of rGO increased the cycling stability of PPy and improved the capacitive performance, thus further demonstrating the positive effects of rGO, achieving a highest specific capacitance of 462.1 F g−1 at a current density of 0.5 A g−1. The present strategy will pave the way for the development of a new generation of advanced electrode materials for energy storage. [ABSTRACT FROM AUTHOR]

The preparation of highly active, low cost and stable electrocatalysts via simple and mild methods for overall water splitting is significant for energy conversion and storage. Herein, we used a nickel selenite complex [{Ni(TMEDA)SeO3}2] to obtain NiSe nanospheres on three-dimensional carbon cloth via electrodeposition. The performance of the as-prepared electrodes (NiSe-TMEDA/CC) was investigated in alkaline solution for water splitting, exhibiting bifunctional OER and HER activity with small overpotentials of 226 and 30.8 mV to achieve a current density of 100 mA cm−2, respectively. Using this bifunctional electrode, a water electrolyzer only required a cell voltage of 1.52 V to deliver a current density of 100 mA cm−2 with excellent long term stability. Compared with the traditional separate Ni and Se sources, the single-molecule precursor is beneficial to form uniform NiSe on the substrate. This work provides a reference for the preparation of bifunctional electrocatalysts for water splitting via single molecule electrodeposition. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs) have been paid more attention in supercapacitors due to their advantages in structure and performance. In particular, NiCo LDHs have been extensively studied due to its high theoretical specific capacity. Unfortunately, the exerted capacity is much lower than the theoretical value due to its poor electron conductivity. In this work, P@NiCo LDHs cabbage-like spheres were successfully synthesized by a mild co-precipitation strategy and a subsequent phosphating treatment method. Owing to the generation of metal phosphides, which is endowed with good electron conduction ability, the specific capacitance of the P@NiCo LDHs (536 C g−1) is 1.88 times greater than the NiCo LDHs (285.8 C g−1) at a current density of 1 A g−1. In addition, the prepared electrode provided a good cycling performance with no difference from the initial capacitance at 10 A g−1 after 5000 cycles. Besides, the symmetric supercapacitor device with vacuum plastic packaging structure was prepared, which exhibits an energy density of 7.83 W h kg−1 at 300 W kg−1. This work indicates that the phosphating strategy is an effective way to improve the performance of LDH-based materials for supercapacitors. [ABSTRACT FROM AUTHOR]

2,6-Diaminoanthraquinone (DQ) molecules were covalently modified onto the surface of graphene (GO) via a nucleophilic displacement reaction between the epoxy groups on the surface of GO and the –NH2 groups of DQ molecules in the presence of ammonia to form a composite material (labeled as DQ–RGO). The rapid reversible faradaic reactions of DQ molecules are realized by means of the good conductivity of graphene. Therefore, the DQ–RGO composite material can combine the Faraday pseudocapacitance of DQ with the double-layer capacitance of graphene, thus displaying outstanding electrochemical performance in acidic electrolyte solution, including a high specific capacitance (332 F g−1 at 1 A g−1), excellent rate capability (the capacitance retention rate is 72.9% at 50 A g−1) and good cycling stability (maintaining 81.8% of the initial capacitance after 5000 cycles). Meanwhile, a thionine-functionalized graphene hydrogel (Th–GH) was also prepared via a non-covalent strategy. Finally, the DQ–RGO composite acted as the negative electrode and Th–GH acted as the positive electrode to construct an asymmetric supercapacitor (ASC). The ASC exhibited an energy density of 14.2 W h kg−1 along with a power density of 0.763 kW kg−1 and long cycling durability (maintaining 80% of the initial capacitance after 8000 cycles at 5 A g−1). More importantly, two such devices in series successfully illuminated 16 red light-emitting diodes (LEDs), demonstrating its outstanding energy storage performance. This work can provide ideas for the construction of green, all-carbon and excellent electrochemical performance devices. [ABSTRACT FROM AUTHOR]

A new composite NbOF–GO and FeOF–GO electrode material was synthesized by the screw-capped pressure tube method for a supercapacitor with specific capacitance values of 599 and 459 F g−1 at current densities of 0.5 and 0.2 A g−1. The NbOF–GO electrode has excellent cycling stability (capacitance retention of 88% after 5500 cycles at a current density of 5 A g−1), possesses a cubic morphology and excellent surface area, and it improves the number of ions near the surface area for charge storage, in addition to shortening the ion distance over a thin dimension and it is reported to have excessive specific capacitance. The synthesized asymmetric supercapacitor (ASC) device produces a maximum voltage of up to 1.2 V, a high specific energy of 51 W h kg−1 and a specific power of 1496 W kg−1, with an excellent cycling lifespan of only 2% capacitance loss after 10 000 cycles. [ABSTRACT FROM AUTHOR]

The design and development of composite materials with novel structures is one of the effective ways to enhance the electrochemical properties of supercapacitors. In this paper, a one-step electrodeposition method is used to adjust the morphology and structure of CoMnS nanomaterials by changing the amount of CS2. CoMnS nanomaterials with unique flower-like structures are reasonably prepared, which promotes the flow of electron transfer and improves the electrochemical behavior. It is worth noting that when the amount of CS2 is 4 mmol, the specific capacitance of CoMnS-4 reaches 3469.5 F g−1 at 1 A g−1, and the specific capacitance is still 2830.5 F g−1 (maintaining 81.56%) until the high current density reaches 20 A g−1. After 10 000 cycles, it shows excellent cycle stability (maintaining 95.78% at 20 A g−1). The CoMnS-4//AC asymmetric supercapacitor device has an excellent energy density of 85.91 W h kg−1 when the power density is 800 W kg−1, which shows it's great application value. [ABSTRACT FROM AUTHOR]

The aim of the present study is to produce high performance Pd-based electrodes for water splitting by a simple and fast preparation technique, and to investigate the impact of substrates and film growth time on electrode performance. The electrodes are prepared in one step by the aerosol-assisted chemical vapor deposition (AACVD) method within 30 to 120 min. Pd is deposited on titanium (Ti) foil and nickel foam (NF). Microscopic analyses indicate the growth of cauliflower-like porous nanostructures of Pd. Electrochemical measurements indicate that the Pd/NF electrode requires only 65 mV and 189 mV, while the Pd/Ti electrode requires 121 mV and 288 mV to produce current densities of 50 and 150 mA cm−2, respectively, for the hydrogen evolution reaction (HER). The respective Tafel slopes for Pd/NF and Pt/Ti are determined to be 29.3 mV dec−1 and 52.3 mV dec−1, suggesting different rate-determining mechanisms of the HER on various substrate surfaces. The better activity of the Pd/NF electrode is attributed to higher electrical conductivity of bare NF and Pd/NF electrodes compared to that of bare Ti and Pd/Ti electrodes, though the charge transfer resistances are discerned to be comparable. The turnover frequency of the Pd/NF electrode is superior to that of Pd/Ti at lower overpotential, which becomes comparable with increasing potential. The results of this study combined with our earlier findings reveal the bi-functional electrocatalytic nature of the nanoscale Pd for possible utilization in an electrochemical water splitting unit for H2 and O2 production. [ABSTRACT FROM AUTHOR]

The exploration and fabrication of highly effective and low cost non-precious electrocatalysts are very essential for the hydrogen production industry. Herein, for the first time we constructed and prepared Ni/CoFe hydroxide and Ni/CoSe2 electrodes with hollow nanotube array structures on conductive nickel foam by a facile two-step electrodeposition method combined with a ZnO self-template strategy. The as-prepared Ni/CoFe hydroxide and Ni/CoSe2 nanotube arrays only need a relatively low overpotential of 230 mV for OER and 89 mV for HER to achieve a current density of 20 mA cm−2 and 10 mA cm−2, respectively. Specifically, an asymmetric alkaline electrolyzer has been assembled by using Ni/CoFe hydroxide as anode and Ni/CoSe2 as cathode, which requires a low overall potential of only 1.57 V at the current density of 10 mA cm−2 and displays excellent stability for 20 h. The excellent electrocatalytic performance of the electrodes benefits from the synergistic effect of the different components and the hierarchical hollow nanotube structure with abundant active sites, fast electronic transport and sufficient diffusion channels for electrolyte and gas. The work provides a feasible way to develop highly efficient, hierarchical, hollow-structured and low-cost earth-abundant catalysts for electrocatalytic water splitting applications. [ABSTRACT FROM AUTHOR]

As the demand for long-term, sustainable, and durable energy storage devices has been increasing, it is important to develop high performance carbon-based electrode materials for energy storage devices using simple, economical, and green techniques. The present study proposes an environment-friendly approach for facile, large-scale synthesis of onion-like carbon nano-particles (CNOs) for their application in high-performance and durable supercapacitors (SCs). CNOs were synthesized by a traditional wick pyrolysis technique using waste frying oil as the free carbon source. The as-synthesized CNO particles were connected to each other to form a chain-like interconnected network, effectively providing accelerated ion-transport, reduced resistance for electron transport and more active sites for charge storage. SCs based on activated CNOs (a-CNOs) demonstrated a gravimetric capacitance of 71 F g−1 in organic electrolytes at a current density of 2 A g−1. Moreover, a-CNOs delivered good volumetric capacitance of 63 F cm−3 with a high packing density of ∼0.89 g cm−3, which is higher than that of the commercial activated carbon. Furthermore, the capacitance retention was ∼80% even after 10 000 galvanostatic charge discharge cycles. Overall, this work presents a method to produce a new type of carbon-based electrode materials from wastes for high performance energy storage devices. [ABSTRACT FROM AUTHOR]