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The theoretical specific capacity of tin dioxide (SnO 2) as a lithium-ion batteries (LIBs) anode material is up to 1494 mAh·g−1, far exceeding that of graphite. However, the low conductivity, volume expansion, crushing failure and particles agglomeration during charge/discharge cycles limit its application in LIBs. In this work, the SnO 2 /MoO 3- x /rGO composite material was synthesized by one-step hydrothermal method, with SnO 2 and amorphous MoO 3- x tightly and uniformly anchored at the surface of reduced graphene oxide (rGO). The results of structural characterization and electrochemical performance evaluation show that amorphous MoO 3- x can increase the reactive active sites, inhibit Sn particles aggregation, and promote the reversible reaction of SnO 2. rGO effectively improves the electrical conductivity of the composite and buffers the volume change of Li-Sn alloying/dealloying during cycles. In addition, due to introduction of MoO 3- x and rGO a stable SEI film can be formed at the material's surface to improve the cycle stability. SnO 2 /MoO 3- x /rGO exhibits excellent rate performance and cycle performance. When the rGO content is 10.9 wt%, the reversible capacity of the composite reach 813 mAh·g−1 after 800 cycles at current density of 1.0 A·g−1, and 450.6 mAh·g−1 after 1000 cycles at current density of 5.0 A·g−1, with the capacity retention rate of 96.9%. [ABSTRACT FROM AUTHOR]

• Defect engineering crystal structures promoted by Zn-substituted MnCo 2 O 4 is first proposed for ZIBs. • Zn//Zn 0.4 Mn 0.6 Co 2 O 4 batteries having excellent specific capacitance and superior capacitance retention is proven. • Long-life cycle with 70 mAh g-1 at 0.2 A g-1 after 800 cycles is achieved. • The ex-situ XPS together with SEM-EDX is employed to confirm the crystal stability and reversibility of Mn2+/Mn4+ and Co2+/Co3+ through cycling. Zinc-ion batteries are regarded as an effective alternative for energy storage because of their low flammability, affordability, inherent safety, and high theoretical capacity. However, manganese-based materials are limited due to a relatively narrow tunneling pathway, causing low-rate capacity and low life cycle stability. Hence, an effective strategy using defect-engineered crystal structure promoted by Zn-substituted MnCo 2 O 4 to achieve a high-performance ZIB is proposed. The microspheres, assembled with interconnected micro- and nanoflake structures of Zn x Mn 1-x Co 2 O 4 (with the Zn-substitution of x = 0, 0.2, 0.4, 0.6, and 0.8), are hydrothermally synthesized, followed by calcination, which serves as the cathode for ZIBs. At the optimal Zn 0.4 Mn 0.6 Co 2 O 4 cathode, ZIBs battery possesses a superior discharged specific capacity of 660 mAh g-1 at 0.05 A g-1, a high-rate performance (energy density of 260–528 Wh kg−1 at a power density of 800–40 W kg−1), and good capacity retention of 70 mAh g-1 after 800 cycles at 0.2 A g–1. Ex-situ SEM-EDX and XPS results through charge/discharge cycles confirm the high stability and reversibility of Zn 0.4 Mn 0.6 Co 2 O 4 in its electron state. Such improved rate capacity and long-life cycles originate from efficient defect engineering using Zn-substitution and oxygen vacancies. These lead to improved ion insertion and Zn2+ transport kinetics, along with enhanced electrical conductivity, resulting in the reversibility reactions of Mn4+/Mn2+ and Co2+/Co3+ upon Zn2+insertion/extraction. [Display omitted] [ABSTRACT FROM AUTHOR]

• Quaternary layered double hydroxides@sulfur-doped carbon dots (MnCoCrV LDH@SCDs) were synthesized by hydrothermal synthesis. • The MnCoCrV LDH@SCDs on nickel foam (NF) exhibited favourable oxygen evolution reaction (OER) kinetics in three different electrolytes: 1 M KOH alkaline water, simulated seawater, and alkaline seawater. • MnCoCrV LDH@SCDs/NF demonstrated impressive performance, displaying lower overpotentials and sustained stability for over 50 h at 10 mA/cm2 in all three electrolytes. • MnCoCrV LDH@SCDs/NF emerged as a highly effective electrocatalyst for promoting seawater oxidation. This research introduces a novel approach to electrocatalysis for sustainable energy generation, revealing the MnCoCrV LDH@SCDs composite supported by nickel foam (NF) as a high-performance catalyst specifically designed for seawater electrolysis. Constructed by incorporating sulfur-doped carbon dots (SCDs) into MnCoCrV layered double hydroxide (LDH) and depositing them onto a nickel foam substrate, this electrocatalyst demonstrates exceptional efficiency in the oxygen evolution reaction (OER) under alkaline seawater conditions. MnCoCrV LDH@SCDs/NF attains a noteworthy current density of 10 mA/cm² with a minimal overpotential of 209.4 mV. Additionally, it demonstrates a reduced Tafel value of 81.5 mV/dec, indicating faster kinetics. The electrode maintains impressive long-term stability, sustaining efficiency for approximately 50 h at a constant current density of 10 mA/cm². The increased surface area and reduced charge transfer resistance contribute to substantial electrocatalytic performance in seawater. This performance is primarily attributed to improved conductivity, resulting from synergistic contributions from high-valence-state vanadium ions and electrochemically active functional groups in SCDs. The MnCoCrV LDH@SCDs/NF electrocatalyst stands out for its intricate features that not only promote efficient electron transfer but also effectively counteract interference from chloride anions in seawater electrolysis. This study underscores the innovative nature of MnCoCrV LDH@SCDs/NF as a pivotal development in electrocatalyst research, offering a promising avenue for harnessing renewable energy from seawater. [ABSTRACT FROM AUTHOR]

• Bimetallic NiMn-LDHs are synthesized using HMTA and urea as precipitating agents by hydrothermal synthesis route. • NiMn-LDH@HMTA shows open structured microflowers, high pore volume (0.24 cc g−1) and pore hierarchy. • NiMn-LDH@HMTA delivers a high specific capacity of 719 C g−1 at 1 A g–1 and excellent capacity retention of 82.6% after 10,000 cycles. • The supercapattery device, NiMn-LDH@HMTA//AC-KOH shows the energy density of 50 and 34 Wh kg–1 at the power densities of 800 and 4000 W kg–1, respectively. In this work, nickel-manganese layered double hydroxides (NiMn-LDHs) are synthesized using hexamethylenetetramine (HMTA) and urea as precipitating agents via hydrothermal synthesis route. The materials have different flower like microstructure and porosity. The effect of microstructures, porosity and mass loading of the LDHs on the overall electrochemical performance is thoroughly studied in this work. It is observed that HMTA assisted NiMn-LDH having open flower like microstructure delivers a high specific capacity of 719 C g −1 at 1 A g–1 and excellent capacity retention of 82.6% and 86% for 10,000 CV and 5000 GCD cycles, respectively. Furthermore, a supercapattery device assembled using NiMn-LDH@HMTA as cathode and activated carbon as anode exhibit high-capacity retention of 80.1% after 5000 GCD cycles along with an energy density of 50 and 34 Wh kg–1 at power densities of 800 and 4000 W kg–1, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

This study synthesizes cuboidal-shaped hierarchical Mn 2 O 3 (MNO) particles using a simple hydrothermal technique with Good's buffer piperazine and examines their electrochemical performance. The research explores how varying piperazine concentrations (piperazine concentration x in MNO- x) affect the structure and electrochemical properties of the MNO particles. X-ray diffraction (XRD) confirms the crystalline nature of MNO while scanning electron microscopy reveals that piperazine concentration influences the particles' shape, size, and morphology. The MNO synthesized with 6 mmole piperazine (MNO-6) has the highest surface area of 8.67 m²/g. Electrochemical tests in 1 M and 6 M KOH electrolytes show that MNO-6 achieves the highest specific capacitance, with 440 F/g in 1 M and 952 F/g in 6 M KOH at a 1 mV/s scan rate. At a 1 A g-1 current density, MNO-6 exhibits a specific capacitance of ∼545.8 F/g in 1 M KOH and 809.0 F/g in 6 M KOH, with corresponding energy densities of 27.3 Wh/kg and 40.4 Wh/kg, and power densities of 315.7 W/kg and 365 W/kg, respectively. The superior electrochemical performance is attributed to the high surface area and porous structure of MNO synthesized with piperazine, highlighting its potential for advanced energy storage applications. [Display omitted] [ABSTRACT FROM AUTHOR]

• A quasi-single-crystal PbO 2 is successfully synthesized by hydrothermal method. • The oriented exposed surfaces are identified as (110) and (101) facets. • The quasi-single-crystal PbO 2 is more conducive to electrochemical ozone production. • The PbO 2 (110) facet is thermodynamically more favorable in the presence of high PVP concentration. The crystal facet of PbO 2 has been proved to be a key factor affecting its electrochemical ozone production (EOP) performance. However, PbO 2 with smooth and uniform crystal surface and single-crystal nature, which is the basis and prerequisite for PbO 2 crystal facet engineering, has not yet been reported. In this study, by adding polyvinylpyrrolidone (PVP) as a facet modifier during the hydrothermal synthesis, a quasi-single-crystal PbO 2 (PVP:Pb(CH 3 COO) 2 ·3H 2 O=48:100, PVP-48) with (110) and (101) exposed facets was successfully synthesized. Compared with commercial PbO 2 prepared by electrochemical deposition, PVP-48 exhibits excellent electrochemical catalytic activity due to its special crystal structure, and achieves the highest current efficiency of 11.9 % at a current density of 0.83 A/cm2. Further calculations show that PVP prefers to adsorb onto the (110) facet of the lead dioxide and reduces its surface energy, thereby exposing the (110) facet more readily. This work demonstrates the importance of PbO 2 facets composition and provides new ideas for further controllable synthesis of PbO 2 with specific facet structure and higher EOP efficiency. [Display omitted] [ABSTRACT FROM AUTHOR]

• SnS 2 nanopetals bonding on the surface of rGO matrix is fabricated by hydrothermal method. • SnS 2 nanopetals @rGO exhibits the high initial reversible capacity (749 mAhg−1 (at 0.2 Ag−1) and 852 mAhg−1 (at 0.1 Ag−1) for SIBs and PIBs respectively. • It exhibits long term cycling stability 50 % (372 mAh g −1 at 0.2 Ag−1 after 2000 cycles) and 58.2 % (496 mAhg−1 at 0.1 Ag−1 after 1500 cycles) of specific capacity for SIBs and PIBs respectively and outstanding rate capability. • SnS 2 nanopetals@rGO prevents the shuttle effect of polysulfide through the formation of in-built C-S bond. Anodes that engage in conversion as well as alloying reactions are highly attractive candidates for sodium/potassium-ion batteries (SIBs and PIBs) because of their high theoretical specific capacities. Herein, Tin sulphide@reduced graphene oxide (SnS 2 nanopetal@rGO) composite material is investigated as an advanced anode material for SIBs and PIBs. In this work, a simple hydrothermal synthesis of ultrathin SnS 2 nanopetals covalently decorated on the surface of rGO is demonstrated as an anode material for SIBs and PIBs. The as prepared SnS 2 @rGO displays an initial charge capacity of 749 (at 0.2 A g −1) and 852 mAh g −1 (at 0.1 A g −1) for SIBs and PIBs respectively. The SnS 2 @rGO hybrid exhibited excellent cycle life which is attributed to the introduction of rGO in the composite as well as the in-built formed C-S bond. Moreover, the rGO matrix, firmly anchored with C–S bonds, envelops the outer SnS 2 , effectively inhibiting direct contact between SnS 2 and the electrolyte. These combined effects contribute to impede the irreversible conversion of sulfur to sulfite, thus ensuring excellent structural stability throughout electrochemical cycling. The well-engineered nanoarchitecture not only guarantees the fast electrode kinetics, but also confirms excellent pseudo capacitance contribution during repetitive cycles which is confirmed by kinetic studies. Thus, SnS 2 @rGO is found to be a most promising electrode for sodium/potassium-ion batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

Materials containing binary transition metals with MoO 4 polyanions exhibit excellent stability, electrical storage capacity, long-term cycling resilience, and high operating voltage. In this study, an oleic acid-assisted hydrothermal synthesis method was used to control the morphology of NaGd(MoO 4) 2 quadrilateral disks (QuDs), and the electrodes based on the controlled morphology of NaGd(MoO 4) 2 QuDs were investigated for the fabrication of supercapacitors. In addition, cyclic voltammetry (CV) and constant current charge/discharge (GCD) analysis were performed to analyze the supercapacitance behavior of NaGd(MoO 4) 2 QuDs based electrode. The NaGd(MoO 4) 2 QuDs with 1.25 mL of oleic acid doped showed a good specific capacitance of ∼249.4 F∙g−1 at 0.01 V∙s−1 and excellent cycling stability, retaining up to ∼93.8% of its initial capacitance after 1000 cycles. Thus, the results indicate that the NaGd(MoO 4) 2 QuDs-based supercapacitor holds great potential as a high-performance option for advancing supercapacitor technology. [ABSTRACT FROM AUTHOR]

• Fe-NiMoO 4 -clusters/NF prepared by one-step hydrothermal method on nickel foam. • The nanorods within Fe-NiMoO 4 -clusters/NF become coarser and align more tightly. • 4% Fe-NiMoO 4 -clusters/NF has excellent Oxygen Evolution Reaction performance. Water electrolysis for hydrogen production has attracted significant scientific interest because it is sustainable, pure, and environmentally benign. Nevertheless, the slow rate of the oxygen evolution reaction (OER) during electrolytic water splitting greatly impedes the progress of its development, leading to higher energy consumption and higher costs during hydrogen production. Herein, Fe-doped NiMoO 4 nanoflower clusters on nickel foam (Fe-NiMoO 4 -clusters/NF) as a superior electrocatalyst for the OER via a facile hydrothermal synthesis method. The material delivers excellent electrocatalytic performance at optimal Fe doping level (4%) with low overpotentials of 170 mV@10 mA cm−2 and 240 mV@100 mA cm−2, a small Tafel slope, and long-term stability. Remarkably, the overall water splitting system assembled with the designed material and NiMoO 4 -clusters/NF exhibits superior stability and a low driving voltage. A comprehensive analysis indicates that Fe doping is crucial to the structure and electrocatalytic properties of NiMoO 4. Fe-doped NiMoO 4 -clusters can serve as stable and efficient OER electrocatalysts in alkaline electrolytes. [ABSTRACT FROM AUTHOR]

Development of electrode materials exhibiting exceptional stability and possessing a high specific capacitance is the important task within the realm of supercapacitor research. In this study, a novel micro-architecture of NiMoO 4 (NMO) resembling a hydrangea in three dimensions (3D) has been developed. The surface of NMO was modified by anchoring PANI nanoparticles and reduced graphene oxide (rGO) resulting in the formation of a composite material designated as NiMoO 4 /rGO/PANI (NMORP). The NMORP composite demonstrates a notable increase in specific-capacity, reaching 1150 C g−1 when tested at 1 A g−1. The observed capacity retention percentage of 97.5 % after undergoing 5000 cycles on a notable current density (10 A g−1) provides substantial proof of exceptional cycling performance within the cycling domain. The remarkable outcomes observed can be attributed to the synergistic impact of the structural and componential characteristics of the NMORP composite. The higher cycling stability of the NMORP composite electrode may be ascribed to the 2D–2D coupling phenomenon occurring at the interface of reduced graphene oxide (rGO) and NMO nanosheets, together with the stable 3-D design reminiscent of hydrangea flowers. Furthermore, the NMORP composite, characterized by a pore structure ranging from 10 to 20 nm and higher conductivity, demonstrates enhanced capabilities regarding the transfer of charge and diffusion of ions. In addition, the NMORP//AC supercapacitor shows a remarkable energy density of 82.43 Wh kg−1 at 850 W kg−1 power density. Furthermore, it shows exceptional cycling performance, retaining 94.5 % of its capacity with 10 A g−1 current density upon the completion of 10,000 cycles. The fabrication of a composite material, referred to as NMORP, presents a viable approach to address the challenges associated with the inadequate electrochemical durability and sluggish electron/ion transfer exhibited by NMO composite when utilized as an electrode in asymmetric supercapacitors (device). [Display omitted] [ABSTRACT FROM AUTHOR]

The functional properties of molybdenum disulfide (MoS 2) are highly dependent on its structure. Here, we present a one-pot hydrothermal synthesis approach allowing to simultaneous control MoS 2 structure over several length scales. Lowering the pH of the hydrothermal precursor solution leads to smaller crystallite sizes of the pristine MoS 2 formed. Moreover, the addition of alkyldiamines to the same precursor solution leads to their physical confinement between the forming MoS 2 layers without the formation of covalent bonds, yielding interlayer-expanded MoS 2. Controlling alkyldiamine precursor concentration can vary the number of confined structural pillars in interlayer-expanded MoS 2. Electrochemical lithium intercalation is tested as a function of MoS 2 structural properties. It is revealed that both smaller crystallite sizes and expanded interlayer-spacing lead to an increasingly pseudocapacitive lithium intercalation signature. The number of lithium that is reversibly stored in interlayer-expanded MoS 2 is increased to almost 1.5 per formula unit. The results provide a facile synthesis approach to simultaneously control MoS 2 crystallite size and d-spacing, which may be of interest for applications beyond lithium intercalation, such as multivalent ion intercalation or electrocatalytic hydrogen evolution. [ABSTRACT FROM AUTHOR]

• A simple and fast hydrothermal synthesis method was proposed in this paper to synthesize an electrode material with a heterostructure of NiMoO 4 nanoneedles and high-performance flower-shaped NiCoZn-LDH on a foam nickel substrate. • The electrochemical performance of the NiCoZn-LDH@NMO@NF nanoneedle composite electrode material, treated with CTAB, is significantly superior to that of the untreated NiMoO 4 @NF electrode. • It shows excellent electrochemical properties, including a specific capacitance of 3541 mF/cm2 in KOH solution and an outstanding capacity retention of 83.04 % after 10,000 cycles. Transition metal hydroxides have attracted wide attention as promising composite nanomaterials due to their numerous active sites and large specific surface areas. In this study, a two-step hydrothermal synthesis method is proposed to generate a heterostructure (NiCoZn-LDH@NiMoO 4 @NF) consisting of nanoflowers coated with nanoneedles on a foam nickel substrate. The aggregation issue of NiCoZn-LDH is effectively improved by immersing it in CTAB solution after one-step hydrothermal synthesis of NiMoO 4 nanoneedles on Ni Foam (NF). The heterostructure between NiMoO 4 nanoneedles and NiCoZn-LDH significantly enhances the material stability and electrochemical performance. Activated carbon is used as the negative electrode, and the NiCoZn-LDH@NiMoO 4 @NF composite material is used as the positive electrode to assemble an asymmetric supercapacitor (ASC) device for electrochemical testing. The device exhibits a specific capacitance of 3541 mF/cm2 at a current density of 6 mA/cm2. Furthermore, the capacity retention rate remains at 83.04 % after 10,000 cycles of charge and discharge, and a high specific energy density of 0.735 mWh/cm2 is achieved at a power density of 1.6 mW/cm2. The experimental results demonstrate that transition metal hydroxides play a crucial role in enhancing the electrochemical performance of supercapacitors. This study provides new insights into Supercapacitor (SC) active materials and offers a promising experimental approach for synthesizing new nanomaterials. [ABSTRACT FROM AUTHOR]

The enormous developments in the area of smart and wearable technology have led to grow interest in innovative and portable energy storage devices. This study described the development and electrochemical behavior of asymmetric supercapacitors with a negative electrode of activated-carbon (AC) and positive electrode of cobalt-molybdate/reduced graphene-oxide/polyaniline (CoMoO 4 /rGO/PANI). The positive electrode materials of CoMoO 4 /rGO/PANI were synthesized using a facile hydrothermal approach. The nanocomposites were characterized using physico-chemical methods including nitrogen adsorption-desorption isotherm analysis, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), X-ray Photon Spectroscopy (XPS) and Raman spectroscopy. The CoMoO 4 /rGO/PANI nanocomposite showed a noticeable specific capacity of 630 C g−1 when tested with three electrodes in 3 M alkaline solution (KOH). The CoMoO 4 /rGO/PANI //AC asymmetric device demonstrated the optimal specific capacitance of 350 C g−1 with an energy density of 96 W h kg−1 with current density of 1.4 A g−1. The assembled device demonstrated enhanced cyclic stability with outstanding capacitance retention of nearly 97 % after 10,000 cycles (at 51 mA cm2 areal-current density). This composite electrode has a lot of promise for usage in wearable technology, flexible electronics, and technological gadgets. [Display omitted] [ABSTRACT FROM AUTHOR]

• The B-incorporated Pd NPs anchored on 3D N-doped graphene was fabricated. • The PdB x /NG reveals impressive electrochemical GOR performance. • The boron-incorporation enables the electronic effect and strain effect for Pd. • The NG endows PdB x /NG with rich pores and abundant N-containing functional groups. The incorporating of metalloid elements into the interstices of Pd lattice is a powerful strategy to manipulate the binding strength of surface adsorbates and thereby to boost its electrocatalytic activity and anti-poisoning for many electrocatalytic reactions. In present work, a novel nanocomposite, the boron-incorporated palladium nanoparticles anchored on the three-dimensional nitrogen-doped graphene (PdB x /NG), was firstly fabricated through a simple hydrothermal synthesis followed by a facile wet chemical reduction method. Extensive physicochemical analyses were conducted to unveil the effects of the boron-incorporation on the properties of the as-synthesized electrocatalyst. More strikingly, the PdB x /NG displayed considerably boosted electrocatalytic behavior towards glycerol oxidation reaction (GOR), which largely outperformed the Pd/NG and benchmark Pd/C. The NG endowed PdB x /NG with three-dimensional architecture, rich pores and abundant nitrogen-containing functional groups. Furthermore, the boron-incorporation enabled the electronic effect (electronic modification) and strain effect (lattice expansion) for Pd. The superior contribution of NG and boron-incorporation enhanced electrocatalytic activity and reinforced stability of PdB x /NG for GOR. This study provides an alternative way for fabricating the boron-incorporated catalysts for electrochemical reactions and beyond. [ABSTRACT FROM AUTHOR]

Zinc Oxide is a semiconductor widely used in sensitized solar cells as an electron transport layer. Among the different nanostructures obtainable for this material, the vertically-aligned ZnO nanorods are of great interest for the design of photoanodes; mainly due to the directionality of charge transport. Vertically-aligned ZnO nanorods of different aspect ratios were prepared via hydrothermal synthesis. UV–Vis absorption was used to determine the dependence of the optical band gap energy on the nanorod diameter according to the Burstein-Moss shift theory due to the presence of surface states. Information about the electronic properties of the different nanorods was obtained by spectroelectrochemical measurements used to monitor the absorbance decrease and Egap shift at different potentials. Time of flight photocurrent transients indicated a dependence on charge transport time with ZnO nanorod length. All evidences point to a large distribution of trap states located in the semiconductor band gap. • Vertically aligned ZnO nanorods of different aspect ratios prepared by hydrothermal method. • The optical band gap depended on the diameter of the nanorods. • Spectroelectrochemical measurements indicated that thinner nanorods are more affected by charge injection. • Time of flight photocurrent transients evidenced a dependence on charge transport time with ZnO nanorod length. [ABSTRACT FROM AUTHOR]

Hydrogen production is an immediate need to replace the fossil fuels to keep environmental balance, and water splitting is an effective solution in presence of catalyst through oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, for the first time, we have synthesized Iron Phosphate Hydroxide (Fe 2.95 (PO 4) 2 (OH) 2) thin film electrode as a superior electrocatalyst by facile hydrothermal method using binder free approach. The crystallographic properties are studied from X-ray diffraction pattern, and Reitveld refinement analysis shows best fit with the tetragonal Lipscombite structure of Iron Phosphate Hydroxide (Fe 2.95 (PO 4) 2 (OH) 2). Flower like structure consist of agglomerated nanorods on micro and sub-micrometric spheres of Fe 2.95 (PO 4) 2 (OH) 2 exhibits lower overpotential of 281 mV at 10 mA/cm2 current density towards OER in alkaline (1 M KOH) medium and maintains its activity after 12 h catalytic stability test. Moreover, prepared electrode shows HER with overpotential 165.7 mV at current density 10 mA/cm2 in acidic (1 M H 3 PO 4) medium and demonstrates enhanced performance (126.4 mV overpotential) after 12 h catalytic stability. The Fe 2.95 (PO 4) 2 (OH) 2 thin film electrodes show superior performance in OER and HER, compared with its oxide counterpart (Fe 2 O 3). Image 1 [ABSTRACT FROM AUTHOR]

V 2 O 3 nanoparticles highly dispersed in amorphous carbon composites (VO-C) were successfully synthesized by the calcination of (NH 4) 2 V 3 O 8 /C precursor, which was fabricated through the hydrothermal reaction using commercial NH 4 VO 3 and glucose as raw materials. The release of gaseous byproduct during the formation of V 2 O 3 and amorphous carbon resulted in the formation of highly dispersed oxide nanoparticles dispersed in porous carbon matrix. The composites exhibited a high specific intercalation pseudocapacitance of 458.6 F g−1 at 0.5 A g−1 with a retention of 86% after 1000 cycles in aqueous electrolyte. Such good electrochemical properties is attributed to the high diffusion coefficient and promoted electron transfer of the composites possibly as a result of surface modification of V 2 O 3 nanoparticles. In addition, highly porous carbon network with homogeneously dispersed V 2 O 3 permits efficient intercalation reaction with much enhanced stability of V 2 O 3. Flexible asymmetric supercapacitors using synthesized VO-C and active carbon electrodes were assembled and demonstrated excellent electrical energy storage performance. [ABSTRACT FROM AUTHOR]

The WO 3 nanosheet@reduced graphene oxide (WO 3 nanosheet@rGO) square particles have been synthesized successfully by a hydrothermal method. The structure and polymorphy of the particle are well characterized by XRD, FT-IR, XPS, SEM, TEM, HRTEM, Raman spectra and BET analysis. The electrochemical behaviors are researched by using CV, galvanostatic cycle and EIS. The results indicate that the special combination about the two-dimension WO 3 nanoplate and graphene scales can promote the electrochemical properties of the metallic oxide effectively. Compared with the pure WO 3 , a higher initial discharge capacity of the WO 3 nanosheet@rGO composite is 1143 mA h g−1, the reversible capacity can also maintain in 1005.7 mA h g−1 after 150 cycles in the condition of 100 mA g−1 and 0.01–3 V. The outstanding electrochemical performances composite demonstrates that WO 3 nanosheet@rGO synthesized by this method is feasible and could be used as a promising anode material for LIBs. Image 1 • The combination of 2D WO 3 nanosheet and graphene at different points reduces the reunion in some degree by a simple hydrothermal method. • The WO 3 nanosheet@rGO remains a high discharge specific capacity of 1005.7 mA h g−1 after 150 cycles at 100 mA g−1. • Incorporating highly conductive the graphene into a 2D nanostructure to enhance the fast charge transfer and a long-term cyclability. [ABSTRACT FROM AUTHOR]

Designing efficient and durable bifunctional oxygen catalyst to replace expensive Pt catalysts in oxygen reduction reaction and oxygen evolution reaction is crucial for various energy conversion devices, such as metal-air batteries and fuel cells. Although various nanocarbon/metal oxides have been developed, their catalytic efficiencies remain unsatisfactory; moreover, bi-functionality and the issue of long-term durability have remained elusive goals. Herein, we report the self-assembly of interconnected nickel-cobaltite nanocrystals on nitrogen-doped graphene via hydrothermal synthesis. The Co3+ sites, the key radicals for bifunctional oxygen reduction and evolution reactions. Well-dispersed nitrogen-doped graphene serve as a platform for anchoring the interconnected nickel-cobaltite nanocrystals and improve the conductivity to maintain a high saturation current in oxygen reduction and low overpotential in evolution reaction, similar to Pt/C. Lifetimes as long as 200 h for oxygen reduction and 300 h for oxygen evolution are demonstrated with negligible degradations. The present approach paves the way for the rational design of various Gr-metal oxide hybrids for numerous applications. Image 1 • Interconnected i -NiCo 2 O 4 grown on nitrogen-doped graphene via self-assembly strategy. • The interconnected nanostructure prevented the migration of nanoparticles. • The electrocatalytic activity was evaluated in oxygen reduction/evolution reactions. • The hybrid exhibited high catalytic activity and long term durability. [ABSTRACT FROM AUTHOR]

A nanohybrid comprises of cobalt-nickel selenide (Co 0.50 Ni 0.50 Se) nanoparticles dispersed on graphene nanosheets (GN) has been synthesized by a simple one-step hydrothermal method to use as a counter electrode for dye sensitized solar cell (DSSC). The structural changes and the corresponding electrocatalytic properties in terms of cathodic peak current density and charge transfer resistance at the electrode/electrolyte interface for Co 0.5 Ni 0.5 Se/GN nanohybrid with respect to the mass ratio between Co 0.5 Ni 0.5 Se nanoparticles and graphene nanosheets have been investigated. Co 0.5 Ni 0.5 Se/GN 0.50 exhibits higher electrocatalytic activity and lower charge transfer resistance than other Co 0.5 Ni 0.5 Se/GN nanohybrids and std. platinum (Pt) counter electrodes. Finally, the DSSC fabricated with Co 0.5 Ni 0.5 Se/GN 0.50 as the counter electrode delivered photo-conversion efficiency (PCE) of 9.42%, which is higher than that of DSSC fabricated with Co 0.5 Ni 0.5 Se (7.59%) and std. Pt (7.68%) counter electrodes. This improved electrochemical performance and higher PCE incited by the synergistic effect of Co and Ni in Co 0.5 Ni 0.5 Se nanoparticles, as well as Co 0.5 Ni 0.5 Se and graphene, could make Co 0.5 Ni 0.5 Se/GN 0.50 nanohybrid as a promising low-cost Pt-free counter electrode for DSSC. Image 1 • Co 0.5 Ni 0.5 Se/GN 0.50 nanohybrid prepared by hydrothermal method which exhibits better reversibility in DSSC. • Their electrochemical properties are optimized by tuning the mass ratio of Co 0.5 Ni 0.5 Se and GN. • Co 0.5 Ni 0.5 Se/GN 0.50 exhibited higher PCE than the std. Pt and Co 0.5 Ni 0.5 Se based CEs. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) has been used to remove salt ions with carbon electrodes by the electrical double layer (EDL) mechanism. Other non-carbon materials based on pseudocapacitive mechanism resulting from faradaic reactions with fast electrosorption/desorption properties have emerged as new promising electrode materials. Until now, pseudocapacitive behavior was limited to thin film electrodes with nanometer thickness and was not yet suitable for practical application. In this work, we employed a two-times of hydrothermal synthesis process constructing MnFe 2 O 4 /Porous rGO (MFO/PrGO) nanostructure as pseudocapacitive electrodes. In this carefully designed architecture, the dense structure of MFO/rGO prepared by first-time hydrothermal process provided good connections of MFO nanoparticle with rGO framework for efficient redox charge transfer; the chemically-etched porous rGO used in the second-time hydrothermal process offered hierarchical pores for easier access of the electrode materials, both contributed in enhanced pseudocapacitive electrosorption. HRTEM verified the MnFe 2 O 4 spinel structure and measured the inter-planar lattice parameter which functioned for ion intercalating in and out of the electrode. The MFO/PrGO electrode resulted in 237 F/g in electrosorption of ions from aqueous solution which was higher than the MFO only electrode. Finally, in the CDI experiment, the great salt electrosorption capacity of 8.9 mg/g and 100% regeneration in multiple cycles were achieved by the MFO/PrGO nanocomposite electrode. These results paved the way for using spinel compounds and graphene nanocomposite electrodes for efficient electrosorption and desalination. [ABSTRACT FROM AUTHOR]

Abstract Cone-shaped CuS@MnS nanostructures were grown on Ni foam with robust adhesion using a one-step hydrothermal method and efficiently served as binder-free battery-type material for high-performance supercapacitors. The synergic effects of the unique nanostructure and great adhesion is advantageous for enhancing the surface area on the Ni foam substrate, increasing the storage and charge accumulation, increasing the electrochemical activity between CuS and MnS, and accelerating electron and electrolyte ion transfer. As a result, as a battery-type material, the CuS@MnS/NF composite electrode exhibited excellent electrochemical performance, including high specific capacity (89.77 mA h g−1 at a current density of 1 A g−1), good cycling stability (95.9% capacity retention after 3000 cycles), and outstanding rate capability compared to that of CuS/NF (45.73 mA h g−1) and MnS/NF (3.8 mA h g−1). This study sheds new light on the composites, and demonstrates that the CuS@MnS/NF electrode is an ideal material for electrochemical energy storage. Highlights • CuS@MnS/NF composite prepared by facile one-step hydrothermal method. • CuS@MnS/NF displays a cone-shaped like nanostructure with greater surface area. • CuS@MnS composite exhibits a higher electrochemical performance than bare CuS and MnS electrodes. • In absence of CuS and/or MnS nanostructures were also prepared for comparison. • Synergic effect plays a key role for providing more active sites for redox reactions. [ABSTRACT FROM AUTHOR]

Abstract The design and development of novel aqueous energy storage devices with high specific energy has recently become the research hotspot. The traditional energy storage devices are severely hindered because of the relatively low specific capacity of carbon anode materials. In this work, a novel aqueous energy storage device is assembled based on flower-like nanosheets-assembled Ni 0.85 Se microspheres as the cathode and porous Fe 2 O 3 nanospheres as the anode. The flower-like nanosheets-assembled Ni 0.85 Se microspheres are synthesized by a two-step hydrothermal method and the porous Fe 2 O 3 nanospheres are prepared through a facile one-step ionic liquid-assisted hydrothermal method. Due to their unique structures and superior electrochemical properties, the as-fabricated Ni 0.85 Se//Fe 2 O 3 asymmetric device manifests high specific energy (39.2 Wh kg−1), high specific power (8.56 kW kg−1) and good cycling stability (82.6% of capacity retention after 5000 cycles). Moreover, two asymmetric devices are connected in series and can easily light a white light-emmitting diode for more than 5 min after being charged to 3.0 V. These impressive results indicate that the rational design of cathode and anode materials for energy storage devices is vitally important, and therefore this work can provide a valuable reference for the design and fabrication of novel energy storage devices with high specific energy and high specific power. Highlights • Flower-like nanosheets-assembled Ni 0.85 Se microspheres are prepared by hydrothermal method. • Porous Fe 2 O 3 nanospheres are prepared through ionic liquid-assisted synthesis route. • A novel aqueous asymmetric energy storage device is fabricated. • The device shows superior electrochemical performance with high specific energy. [ABSTRACT FROM AUTHOR]

Abstract Co(OH) 2 @FeCo 2 O 4 nanocomposite was successfully synthesized via a facile one-step hydrothermal reaction without thermal treatment. The structure and chemical composition of as-synthesized Co(OH) 2 @FeCo 2 O 4 was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. The results show the FeCo 2 O 4 nanosheets are covered with the Co(OH) 2 nanoparticles and the BET show the nanocomposite possess the mesoporous structure with specific surface area and total pore volume are 93.071 m2 g−1 and 0.37 cm3 g−1, respectively. In addition, the electrochemical performances were investigated in a three-electrode system to evaluate the material. The as-synthesized Co(OH) 2 @FeCo 2 O 4 nanocomposite exhibits a high specific capacitance of 1173.43 F g−1 at 1 A g−1 and remarkable cycling stability with 95.4% capacitance retention after 5000 cycles. The results show the higher capacitance and longer cycle performance, compared with the Co(OH) 2 and FeCo 2 O 4 , respectively. This remarkable electrochemical performances were mainly due to mesoporous structure and the synergistic effect of Co(OH) 2 and FeCo 2 O 4. It means that this nanostructure Co(OH) 2 @FeCo 2 O 4 synthesized by this simple and cost-effective method would have more hopeful prospects in energy storage applications. Graphical abstract Co(OH) 2 @FeCo 2 O 4 nanocomposite applied as electrode of supercapacitor shows an impressive enhancement of the performance including the areal capacitance and cycling stability. Image 1 [ABSTRACT FROM AUTHOR]

Abstract The present paper reports the effect of nitrogen modification on photoelectrochemical (PEC) water oxidation behavior of Bi 2 O 3 semiconductor thin film. The semiconductor particles were synthesized via hydrothermal route using Bi(NO 3) 3 as a Bi3+ ion precursor and urea as the nitrogen source followed by drop-cast the particles and annealing the film at 600 °C. The synthesized Bi 2 O 3 exhibited band gap energy of 3.01 eV, calculated from the UV–visibleabsorption spectrum which decreases to 2.75 eV through N-modification. Water oxidation behavior of the material has been tested through linear sweep voltammetry under periodic illumination. Highest photo-current of 180 μAcm−2 has been measured for water oxidation reaction at 0.95 V vs. Ag/AgCl, under illumination of 35 mWcm−2. N-incorporation can enhance the photocurrent up to 50% whereas the visible responsiveness of the material improves significantly as confirmed from electrochemical action spectra and UV–visible absorption spectra. The photocatalytic activity of the semiconductor particles was confirmed through decoloration of Rhodamine-B dye, by spectrophotometric measurements. Graphical abstract Image 102315 [ABSTRACT FROM AUTHOR]

Abstract Nickel cobalt oxide is widely applied to energy storage devices owing to the high electrical conductivity and abundent redox states. To gain more redox reactions for storaging charges, more metals are incorporated in nickel cobalt oxide to synthesize the multiple metallic oxides. The effects of the synthesizing parameters such as temperature, reaction time, and precursor concentration on the morphology and the electrochemical performance for nickel cobalt based multiple metallic oxides have been intensively discussed in the previous reports. However, the ratio of the metals in the nickel cobalt based multiple metallic oxides is rarely investigated. To more understand the growth and the energy storage ability of the efficient nickel cobalt based multiple metallic oxides, the nickel cobalt molybdenum copper oxide is synthesized on the nickel foam using a facile one-step hydrothermal synthesis in this study for the application on the battery-type electrode for the battery supercapacitor hybrid device. The ratios of the four metals in nickel cobalt molybdenum copper oxide are varied to examine the effect of the metal ratio on the morphology, electrical conductivity, charge transfer resistance and the specific capacitance of the electrodes. The optimized nickel cobalt molybdenum copper oxide electrode shows an areal capacitance of 3.54 F/cm2 corresponding to the capacity of 1.67 mAh/cm2 at 5 mA/cm2, due to the preferable wire-in-sheets morphology and the high electrical conductivity. The battery supercapacitor hybrid device with the optimized nickel cobalt molybdenum copper oxide positive electrode and an activated carbon negative electrode shows an areal capacitance of 0.93 F/cm2 corresponding to the capacity of 0.41 mA h/cm2 at 10 mA/cm2 and a maximum energy density of 13.99 Wh/kg at the power density of 340.42 W/kg. The excellent cycling stability with the areal capacitance retention of 61% after 3600 times repeated charge/discharge process and the Coulombic efficiency of higher than 90% for the entire measurement is also achieved for the battery supercapacitor hybrid device. This study provides careful discussion on the morphology and the electrochemical property relating to the metal ratio for preparing the nickel cobalt molybdenum copper oxide electrode. Graphical abstract Image 1 Highlights • Nickel cobalt molybdenum copper oxide (NCMC) is made using hydrothermal synthesis. • The NCMC electrode is prepared for the battery supercapacitor hybrid device (BSH). • Metal ratio effect on physical and electrochemical properties of NCMC are studied. • The optimized NCMC electrode shows an areal capacitance of 3.54 F/cm2 at 5 mA/cm2. • BSH shows a maximum energy density of 13.99 Wh/kg at power density of 340.42 W/kg. [ABSTRACT FROM AUTHOR]

Abstract In this study, we develop hydroxyapatite coatings that consist of micrometric hexagonal crystals grown on the Ti/TiO 2 substrate. The coatings are synthesized by a hydrothermal method. The advance of our hydrothermal approach lies in the concomitant use of two reagents: ethylenediamine tetraacetic acid and monoethanolamine. The phase identification, surface morphology, and elemental composition of structures are examined by x-ray diffraction, Raman spectroscopy, scanning electron microscopy and energy dispersive x-ray spectroscopy. We also assess the in vitro bioactivity of hydroxyapatite structure and uncoated materials after incubation in the SBF solution. Simultaneously, we conduct a series of experiments to investigate electrochemical properties of titanium with and without hydroxyapatite by the means of electrochemical impedance and potentiodynamic polarization experiments in the Ringer's solution. Our results show that monoethanolamine-assisted hydrothermal method is an efficient and promising approach to obtain hydroxyapatite coatings with excellent crystal quality and Ca/P ratio close to the stoichiometric value of the Ca 10 (PO 4) 6 (OH) 2 phase. The SBF immersion tests indicate high bioactivity of hydroxyapatite coating after 7 days of incubation. However, the hydroxyapatite coating does not improve the corrosion behavior of the metallic titanium substrate. Electrochemical studies of all structures show the highest corrosion resistance for the Ti/TiO 2 surface as compared to other samples. The lowest value of corrosion current density (j cor = 0.65 ± 0.19 nA cm−2) is found for the Ti/TiO 2 surface. This result could be attributed to the porous morphology of the hydroxyapatite layer which could favor direct flow of electrolyte between the corrosive medium and the titanium substrate or to the adverse effect of hydrothermal synthesis on the barrier properties of the TiO 2 intermediate layer. [ABSTRACT FROM AUTHOR]

Abstract The specific surface area and pore size of illustrative electrode material is a promising task to achieve better performance of energy storage devices. In this respect, Mg-substituted Ni 1-x Mg x Co 2 O 4 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) samples were synthesized by cost-effective and facile hydrothermal method. As-prepared samples were evaluated as the electrode material for a battery application. The structural and electrochemical characterization analysis has been carried out systematically. Among different samples, NMC50 (x = 0.5) exhibit highest BET surface area of 61 m2g-1 with a suitable pore volume of 0.3029 cm3g-1 and narrow pore size distribution of 2–10 nm. It is verified that the special features of the NMC50 including uniformity of the surface texture and porosity bring significant effect on the electrochemical performances. Consequently, the excellent specific capacity of 302 mAhg−1 is observed for NMC50 sample at a current density of 1.1 Ag-1 and a remarkable cyclic stability of ∼95% is maintained over 2000 continuous charge-discharge cycles. The improved electrochemical performance of NMC50, undoubtedly makes it worth as an excellent electrode material for high-performance energy storage applications. Graphical abstract Image [ABSTRACT FROM AUTHOR]

Abstract The reunion of Sn is always a troublesome issue when it's used as the energy storage materials, on the one hand it comes from the preparation process due to its low melting point, and on the other hand it comes from the Li-Sn alloying process because of its natural tendency of migration. The Sn/SnO 2 /spherical graphene composite prepared by one-step low temperature hydrothermal reduction method can effectively solve this problem. In the composite, Sn/SnO 2 tiny nanoparticles with average diameter of 5 nm distribute evenly between multilayers of graphene sheets presenting a hollow spherical structure. The introduction of SnO 2 can effectively restrain the agglomeration of Sn nanoparticles during alloying process since an amorphous Li 2 O matrix is formed to separate the adjacent active particles. The sandwich graphene hollow sphere skeleton effectively buffers the volume expansion of Sn/SnO 2 and further restricts their migration and agglomeration. Due to the above advantages, the nano-Li 2 O generating from the decomposition of SnO 2 can contact closely with excessive nano-Sn in restricted area, promoting facile conversed conversion reaction. Therefore, the composite exhibits high reversible capacity and excellent cycle performance. A stable and high specific capacity of 843.8 mAh g−1 is obtained after 100 cycles at 0.1 C. Graphical abstract Image Highlights • Tiny Sn/SnO 2 NPs sandwiching between SG is designed to solve Sn anode's problem. • Sn/SnO 2 /SG is prepared by one-step low temperature hydrothermal reduction method. • Li 2 O generated from SnO 2 acts as buffer matrix for Sn at subsequent alloy process. • Li 2 O and excess nano-sized Sn can react easily to reversibly transform into SnO 2. • Excellent cycle stability is presented in Sn/SnO 2 /SG composite. [ABSTRACT FROM AUTHOR]

• Here, we synthesized a novel hierarchical NiCo-LDH@MoS 2 /CuS heterostructure (HS) by facile two-step hydrothermal synthesis. • The hierarchical structure and heterostructures synergistic effect contributes in trifunctional electrocatalyst for water splitting and supercapacitor. • The electrochemical cell required only 1.57 V to achieve overall water splitting in an alkaline medium. • The NiCo-LDH@MoS 2 /CuS HS demonstrate the electrochemical specific capacitance of 1059 f g−1 (or 147.16 mAh g−1) at a current density of 0.2 a g−1. • The FSSC device displays a maximum energy density of 152.60 W h kg−1 at a current density of 0.2 a g−1 with a retention rate of 90.05 % after the 7000 cycles. The development of highly active and long-lived multifunctional electrocatalysts is a key priority to boost clean renewable energy technologies. It is difficult to construct such hierarchically structured materials with an efficient synergistic heterostructure technique to improve electrochemical performance. Here, a novel hierarchical NiCo-LDH@MoS 2 /CuS heterostructure (HS) was prepared by facile two-step hydrothermal synthesis for water splitting and supercapacitor applications. The hierarchical network of NiCo-LDH is grown on MoS 2 /CuS and is put forward based on various physio-chemical analysis. The hierarchical structure and heterostructure synergistic effect result in excellent HER (114 mV@10 mA cm−2) and OER (310 mV@10 mA cm−2) activity. Two electrode water-splitting cells (NiCo-LDH@MoS 2 /CuS||NiCo-LDH@MoS 2 /CuS) achieved a cell potential of 1.57 V@10 mA cm−2. NiCo-LDH@MoS 2 /CuS also exhibits the electrochemical charge storage property of 147.16 mAh g−1@0.2 A g−1. NiCo@MoS 2 /CuS||AC flexible solid-state asymmetric supercapacitor (FSSC) demonstrated charge storage of 226.08 mAh g−1 and energy density of 152.60 W h kg−1@0.2 A g−1 with 90.05 % retention rate, demonstrated the excellent cyclic and structural stability. The acquired knowledge from this study could be a novel strategy for designing hierarchical LDH-based heterostructures as electrode materials for water splitting and energy storage devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Ni(OH) 2 have attracted great attention as pseudocapacitor electrode materials due to its high theoretical capacitance. However, the intrinsic disadvantaged in low electronic conductivity and sluggish ion diffusion kinetics of Ni(OH) 2 limit its performance and practical application. Herein, we report a simple hydrothermal method to synthesize Co doped Ni(OH) 2 and NiOOH array structure on vertical hanging Ni foam. Compared with traditional hydrothermal methods, vertical hanging Ni foam provide sufficient reaction sites and ensure fully growth of array structure, leading to large mass loading of active materials. The array structure and the wide interlayer spacing due to interlayer embedded CH 3 COO− together build an effcient ion diffusion path. Morevoer, strong electron exchange between Ni(OH) 2 or NiOOH and Ni provide high electrical conductivity at the interface, forming the fast and complete electron transport channel inside the electrode. As a result of robust electrochemical kinetics, NiCoLDH@vNF-12 shows a high capacitive and outstanding rate performance of 952.9 C g −1 at 1 A g −1 and 660.0 C g −1 even at 50 A g −1. [ABSTRACT FROM AUTHOR]

• A novel MoS 2 is prepared through facile hydrothermal method. • An interesting nano-worm based aggregates morphology and crystallinity of MoS 2 is obtained. • Excellent electrode material along good specific capacitance and high energy density is attained. • MoS 2 is believed to be a potential electrode material for asymmetric supercapacitor as shown in manuscript. Nowadays, supercapacitors and batteries are trending electrochemical energy storage devices. However, their low energy density and uncertain power density limited their applications, respectively. Recently, the latest innovation in energy storage devices, called hybrid supercapacitors, has appeared as an eventual energy storage device that demonstrates a hybrid storage mechanism of both supercapacitors and batteries. In this work, MoS 2 has been prepared by the facile hydrothermal method, characterized by different techniques, and applied as an electrode in supercapacitors and supercapatteries. The XRD patterns and EDX confirm the successful synthesis of MoS 2 with an average crystallite size of 62.25 nm, while the SEM images show the randomly oriented nanoworms of MoS 2. The XPS spectrum depicts the presence of variable oxidation states of molybdenum (Mo4+and Mo6+) in the MoS 2. The electrochemical performance shows that the highest specific capacitance and specific capacity reached 1866.66 F/g and 1119.99 C/g, respectively, at a scan rate of 5 mV/s for MoS 2. The asymmetric supercapacitor device is made from (Graphite/MoS 2) using as a working electrode and activated carbon as a cathode, which are separated by filter paper. Furthermore, the Dunn's model is utilized to evaluate of capacitive and battery mechanisms and shows the dominant role of diffusive and surface-controlled developments at low and high scan rates, respectively, owing to the change in diffusion time of electrolyte species. The fabricated device shows an energy density and power density of 103.51 Wh/kg and 3807.59 W/kg at a current density of 1 and 7 A/g, respectively, with 93.52% capacity stability and 99.8% coulombic efficiency. This excellent performance of MoS 2 is believed to be a potential electrode candidate for asymmetric supercapacitor applications. [ABSTRACT FROM AUTHOR]

Abstract Different numbers of N/Ti3+ codoped triphasic TiO 2 layer are deposited on TiO 2 nanotube arrays by hydrothermal reaction of TiN and TiO 2 nanotube arrays. The crystal structure, morphology, and composition of the as-prepared samples and their photoelectrochemical properties are investigated and discussed. There are obviously red shift of the optical edge and enhanced visible light absorption for the resulting samples in the ultraviolet–visible diffuse reflectance spectroscopy. Besides, the photoelectrochemical tests indicate that the N/Ti3+ codoped triphasic TiO 2 -TiO 2 nanotube array samples exhibit an enhanced photocurrent density and photovoltage under visible light irradiation. The maximum photoconversion efficiency of N/Ti3+ codoped triphasic TiO 2 -TiO 2 nanotube array sample is 2.1 times higher than that of pristine TiO 2 nanotube arrays. In addition, reduced impedance, higher carrier density, and excellent stability of photoelectrochemical performance of N/Ti3+ codoped triphasic TiO 2 -TiO 2 nanotube array samples are also demonstrated. Finally, a plausible mechanism for the charge migration and separation on N/Ti3+ codoped triphasic TiO 2 -TiO 2 nanotube array samples is proposed. This study provides a novel strategy to design and fabricate visible-light-driven TiO 2 based composites and promote their applications in the field of solar energy utilization. Graphical abstract In situ growth of N/Ti3+ codoped triphasic TiO 2 layer on TiO 2 nanotube arrays to construct homojunctions is achieved via hydrothermal reaction of TiN and TiO 2 nanotube arrays and better photo-electrochemical performance is demonstrated. Image 1 [ABSTRACT FROM AUTHOR]

Abstract Although hard carbon is deemed to be the most potential industrialized sodium-ion batteries anode material, there are still some problems need to be solved. In this study, a waste biomass of reed straw is pretreated by using a new strategy-hydrothermal treatment instead of pickling and successfully transformed to hard carbon materials through subsequent carbonization process. The reed straw carbonized at 1300 °C exhibits an impressively high reversible capacity of 372.0 mAh g−1 with excellent initial coulombic efficiency of 77.03% and outstanding cycling stability. Significantly, the sodium storage mechanism in our electrodes is mainly summarized into two models. Moreover, we find the interlayer spacing of graphite-like nanocrystal of obtained hard carbon influences the sodium ion diffusion ability, thereby affecting the rate performance. Our work offers a simple and eco-friendly way for converting biomass to highly capacity carbon as well as a towardly anode material for sodium-ion batteries, which will open up new avenues of other biomass carbon materials with promising applications. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract Molybdenum disulfide/nitrogen-doped carbon nanocomposite can afford high capacity, good rate capability and cycling stability in lithium ion batteries owing to the synergistic effect from these two components. Structure of the material has a great impact on the performance as well. In this work, MoS 2 /nitrogen-doped carbon (MoS 2 /C) composites have been developed by manipulating the nano-featured polypyrrole templates to guide and confine their growth. They are formed via a simple hydrothermal process combined with a subsequent annealing process. The MoS 2 /nitrogen-doped carbon nanotubes (MoS 2 /CNT) composite with 76% of MoS 2 exhibits an excellent performance including a high capacity of 1232 mAh g−1 at a current density of 0.1 A g−1, outstanding rate capability (947 mAh g−1 at 2 A g−1), and good cycling stability with 754 mAh g−1 retained over 1000 charge/discharge cycles at a high current density of 1 A g−1. This performance is much better than that MoS 2 /nitrogen-doped carbon nanoparticles (MoS 2 /CNP) composite. This work demonstrates the importance of introducing three-dimensional nanostructures in electrode materials to improve their electrochemical performance. [ABSTRACT FROM AUTHOR]

Abstract In the present work, self-assembled 3D flower-like β-Ni(OH) 2 @CDs hybrid nanostructures were synthesized by a simple and low-cost procedure using the CTAB-assisted hydrothermal method. Characterization of synthesized nanocomposite was performed by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), FT-IR and electrochemical techniques. Then, this product was used to fabricate a new nitrite sensor by drop casting 5 μl of its suspension (5 mg/mL prepared in Milli-Q water) on a cleaned glassy carbon electrode surface. The effects of some parameters on the sensor response toward the electro-oxidation of nitrite such as pH, and scan rate were evaluated and optimized to achieve higher sensitivity. The novel amperometric sensor exhibited excellent electrocatalytic activity toward the electro-oxidation of nitrite in the linear range of concentration 2.5 × 10−6 M to 1.2 × 10−3 M with a low detection limit of 0.03 μM (S/N = 3) and very good detection sensitivity of 647.8 μA mM−1 cm−2. The favorable advantages such as good repeatability and reproducibility, high sensitivity, long-term stability and anti-interference make this sensor very attractive for on-site environmental monitoring of nitrite in water samples with satisfied recovery. Graphical abstract Image 1 Highlights • Self-assembled 3D flower-like β-Ni(OH) 2 @CDs was synthesized by the CTAB-assisted hydrothermal method at low temperature. • The important advantages of this synthesis are the simplicity, green wet-chemicals method and low temperature. • The fabricated sensor based on β-Ni(OH) 2 @CDs can enhance electrocatalytic activity towards the oxidation of nitrite. • The main advantage of this sensor is a wide linear range with very low detection limit compared with other sensors. • The unique features of the β-Ni(OH) 2 @CDs make it as a promising candidate to fabricate sensors applicable in environmental field. [ABSTRACT FROM AUTHOR]

Abstract A novel porous electrocatalyst of reduced graphene oxide (RGO)-wrapped NiSe 2 -Ni 0.85 Se hollow microspheres (RNHM) has been synthesized via one-pot hydrothermal process, which is facile, cheap and easy to realize scalable manufacture. Compared to bare NiSe 2 , Ni 0.85 Se and NiSe 2 -Ni 0.85 Se hollow microspheres (NHM), RNHM shows outstanding hydrogen evolution properties with a low Tafel slope value of 31.3 mV dec−1, a low onset potential of −175 mV (vs RHE), and a high cathode current density of 37 mA cm−2 (at ∼ −240 mV vs RHE). More importantly, it shows excellent HER stability after 2000 CV cycles. That superior performs of RNHM can be attributed to the well-designed hollow microsphere architecture with rich porosity and high specific surface area, which provides abundant active sites for HER. In addition, the two-dimensional graphene nanosheets can not only act as a highly conductive matrix facilitating the charge transfer during the process of HER, but also work as a flexible skeleton guaranteeing excellent structural stability. This study provides a novel and rational architecture design strategy of Pt-free catalysts with superior performances and outstanding stability for hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

Abstract In this paper, N-doped reduced graphene oxide and MnO 2 nanocomposite (N-RGO/MnO 2) was synthesized via hydrothermal method, which was used to modify the glass carbon electrode (GCE) for electrochemical detection of Hg2+. p -phenylenediamine was used as the nitrogen source and "bridging" molecule between MnO 2 and RGO. The electrochemical sensing performance towards Hg2+ was evaluated by square wave anodic stripping voltammetry method. The presence of N-RGO/MnO 2 nanocomposite has enhanced the electrochemical performance of the GCE toward Hg2+. The N-RGO/MnO 2 nanocomposite modified electrode was found to have a good sensitivity toward Hg2+ and the favorable sensitivity (72.16 μA/μM) and LOD (0.0414 nM) for Hg2+ were achieved under the optimized conditions. Moreover, the modified electrode possessed a good stability and reproducibility. The excellent performance can be attributed to the characteristic nanostructure and N-doping property of the N-RGO/MnO 2 nanocomposite. This electrochemical sensing strategy is expected to enrich the application field of electrochemical determination and does good to the issue of environment pollution analysis. [ABSTRACT FROM AUTHOR]

Abstract The carbon material derived from citrus peel was prepared via hydrothermal synthesis method with low amount of ZnCl 2. The morphology and surface structure of the synthesized carbons were characterized by field emission scanning electron microscope (FESEM), X-ray diffraction (XRD) and N 2 adsorption/desorption isotherms measurements. The electrochemical and capacitive deionization performance of carbon materials were comparatively studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge (GCD). Compared with the materials activated with KOH or H 3 PO 4 , ZnCl 2 -activated carbon showed the best electrochemical double-layer characteristics, with the specific capacity of 120 F g−1. When being applied as anode in the capacitive deionization (CDI) cell, the desalination amount of 16 mg g−1 and the average salt adsorption rate (ASAR) of 0.67 mg g−1 min−1 were achieved, which is much higher than those of KOH- and H 3 PO 4 -activated materials. The desalination amount retained 80% after 35 cycles. The possible mechanism is proposed in light of X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) analysis. This work provides a facile and environmentally friendly method for the preparation of a green and low cost biomass derived porous carbon material by fruit waste with a low amount (1% mass) of activation regents for high performance capacitive deionization. Graphical abstract Image 1 Highlights • The porous carbon derived from fruit waste was prepared via hydrothermal synthesis method. • The carbon activated with low amount (1% mass) of ZnCl 2 showed the best porous characteristics. • The ZnCl 2 -activated carbon exhibited the best electrochemical and desalination performance. • The +C-Zn||AC cell shows high desalination rate and excellent desalination and regeneration stability. [ABSTRACT FROM AUTHOR]

High mass loading Co 3 O 4 /CoS-based composites are constructed on Co foam through a one-pot hydrothermal process. Most importantly, when a Ni foam acting as counterpart support is introduced, components, morphologies and structures of composite on Co substrate significantly change: Micro-sized Co 3 O 4 /CoS transforms into hierarchical Co 3 O 4 /CoS/Ni(OH) 2 nanocomposite. In addition, the areal loading of Ni counterpart-induced Co 3 O 4 /CoS/Ni(OH) 2 nanocomposite reaches 14.72 mg cm −2 , and it exhibits excellent electrochemical performances: Its electrode possesses an areal capacitance of 14768 mF cm −2 at a current density of 10 mA cm −2 and 95.8% capacitance retention after 10000 cycles, while its asymmetric supercapacitor successfully delivers an energy density of 25.4 Wh kg −1 at a power density of 81.8 W kg −1 (or 12.34 Wh kg −1 at a power density of 1632.9 W kg −1 ) and 90.8% capacitance retention after 20000 cycles at a current density of 200 mA cm −2 . Furthermore, two asymmetric supercapacitor devices connected in series easily drive a red light emitting diode. This work opens a new strategy in preparing ultrahigh areal capacitance supercapacitor electrodes. [ABSTRACT FROM AUTHOR]

It is still a great challenge to improve the rate capability and cyclability of a new conversion-type anode material, VPO 4 , for lithium-ion batteries. In this work, three-dimensional graphene, carbon and in situ formed V 2 O 3 with high theoretical capacity are introduced into VPO 4 to improve the capacity, rate performance and cycle performance. The three-dimensional graphene (3DG) modified VPO 4 /C (VPO/C@3DG) are prepared by a combination of hydrothermal reaction, freeze-drying and calcination processes, and the VPO/C@3DG composite is investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectrum and electrochemical tests. The results indicate that VPO/C@3DG composite contains VPO 4 , V 2 O 3 , carbon and three-dimensional graphene, and dispersive VPO 4 and V 2 O 3 nanoparticles and carbon form carbon coated sphere-like VPO/C particles, and VPO/C particles are covered by three-dimensional graphene. The VPO/C@3DG composite exhibits much higher capacity, better rate capability and cyclability than the control VPO 4 /C and three-dimensional graphene (3DG). In the voltage range of 0.01–3.0 V (vs Li + /Li), the second cycle discharge capacities of VPO/C@3DG are 654.6, 551.6, 486.8, 420.6 and 343.1 mAh∙g −1 at 0.2, 0.5, 1, 2 and 5C (2750 mA g −1 ), respectively, significantly higher than 507.8 (0.2C), 384.9 (0.5C), 294.2 (1C), 219.3 (2C) and 124.1 mAh∙g −1 (5C) of VPO 4 /C and 393.1(0.2C), 298.2 (0.5C), 252.1(1C), 217.8 (2C), 169.7 mAh∙g −1 (5C) of 3DG. After cycled 30 cycles at 0.2C, the discharge capacity of VPO/C@3DG still remains 631.9 mAh∙g −1 , while the discharge capacities of VPO 4 /C and 3DG are 352.4 and 308.5 mAh∙g −1 , respectively, under the same conditions. Even at high current rate of 5C, the discharge capacity of VPO/C@3DG is 338.8 mAh∙g −1 after 100 cycles, significantly higher than that of VPO 4 /C (101 mAh∙g −1 ) and 3DG (142.1 mAh∙g −1 ). The results indicate that the special composition and microstructure are responsible for the superior electrochemical performance of VPO/C@3DG. The results suggest that introduction of three-dimensional graphene and construction of special microstructure is substantially beneficial for improvement of electrochemical performance of conversion-type electrode materials. [ABSTRACT FROM AUTHOR]

Uniform Fe-doped NiS 2 octahedrons with the size of ∼250 nm have been prepared by a hydrothermal method. The as-synthesized Fe-doped NiS 2 octahedrons exhibit excellent electro-catalytic activity for the reduction of triiodide to iodide in dye-sensitized solar cells (DSCs). The DSC with Fe-doped NiS 2 octahedrons CE demonstrates a power conversion efficiency (PCE) of 8.01%, higher than those of NiS 2 CE (6.90%) and FeS 2 CE (4.13%). The enhanced efficiency is attributed to the synergistic effect between Ni and Fe ions in Fe-doped NiS 2 octahedrons. Density functional theory (DFT) calculations reveal the adsorption energy of I ( E I ad) increases from −0.14 eV (NiS 2 ) to −0.65 eV (Fe-doped NiS 2 ) after Fe doping, leading to an enhanced solar cell performance. This study indicates that the Fe-doped NiS 2 octahedron is a promising substitute to develop non-Pt CEs in DSCs. [ABSTRACT FROM AUTHOR]

Super-slenderness-ratio, chestnut-shell-like ZnO, ZnO flowers, ZnO nanorods (NRs), and ZnO nanoparticles (NPs) were synthesized as photocatalysts using a facile hydrothermal method. To enhance its photocatalytic H 2 production rates, Pt serving as a co-catalyst was loaded onto the surface of ZnO to form a Schottky heterostructure. A series of different Pt-modified chestnut-shell-like ZnO, ZnO flowers, ZnO NRs and ZnO NPs were prepared, and their photochemical water-splitting ability was investigated in detail. X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy results confirmed that approximately 5–10-nm-diameter Pt NPs were well dispersed on three-dimensional (3D) chestnut-shell-like ZnO, ZnO flowers, ZnO NRs, and ZnO NPs matrixes to form a Pt/ZnO heterojunction. Low-band-gap energies (minimum value 2.83 eV) and low electron-hole recombination rates were confirmed by ultraviolet–visible diffuse reflectance spectra and photoluminescence spectra, respectively, which demonstrated that the Pt-modified 3D chestnut-shell-like ZnO composites have excellent photochemical properties. The time-course I - t cycles and photocatalytic H 2 production rate cycle measurements for the photocatalyst confirmed that the photochemical performance of Pt-modified ZnO nanocomposite have superstability and altitudinal reusability. The photochemical water-splitting results confirmed that the optimal sample was 4-wt.%-Pt-modified ZnO composites, the H 2 production rate of which was approximately1.97 mmol h −1  g −1 , which was approximately 4, 2.7, 3.2, and 5.8 times that of pristine chestnut-shell-like ZnO, 4-wt.%-Pt modified ZnO flowers, ZnO NRs, and ZnO NPs, respectively. This indicated that 4-wt.%-Pt-modified chestnut-shell-like ZnO exhibits excellent photocatalytic performance. [ABSTRACT FROM AUTHOR]

Herein, TiO 2 microspheres were synthesized at different pH values. The effects of pH values on surface states and charge transport performances were investigated. It is noted that alkaline environment leads to a negative band edge of TiO 2 microsphere and promotes the interfacial charge transfer. Meanwhile, the charge recombination in the TiO 2 microspheres was effectively suppressed in alkaline environment. Besides, TiO 2 microspheres synthesized in alkaline condition contained less surface states, which is beneficial to a higher charge collection efficiency and longer diffusion length in dye sensitized solar cells (DSSCs). Moreover, a better crystallinity of TiO 2 microspheres can be obtained in an alkaline environment. As a result, when these TiO 2 microspheres were used in DSSCs, the device with the TiO 2 synthesized at pH = 8 showed the highest performance than that of the device based on TiO 2 synthesized in lower pH values. [ABSTRACT FROM AUTHOR]

In this paper, we explore the successful hydrothermal approach to make Co 3 (PO 4 ) 2 ·4H 2 O/GF micro-flakes composite material. The unique sheet-like structure of the graphene foam (GF) significantly improved the conductivity of the pristine Co-based material, which is a key limitation in supercapacitors application. The composite electrode material exhibited superior capacitive conduct in 6 M KOH aqueous electrolyte in a 3-electrode set-up as compared to the pristine cobalt phosphate material. The material was subsequently adopted as a cathode in an asymmetric cell configuration with carbonization of Fe cations adsorbed onto polyaniline (PANI) (C-Fe/PANI), as the anode. The Co 3 (PO 4 ) 2 ·4H 2 O/GF//C-FP hybrid device showed outstanding long life cycling stability of approximately 99% without degradation up to 10000 cycles. A specific energy density as high as 24 W h kg −1 , with a corresponding power density of 468 W kg −1 was achieved for the device. The results demonstrated the efficient utilization of the faradic-type Co 3 (PO 4 ) 2 ·4H 2 O/GF composite along with a functionalized carbonaceous electric double layer (EDL)-type material to produce a hybrid device with promising features suitable for energy storage applications. [ABSTRACT FROM AUTHOR]

In order to seek a cost-effective and facile approach to synthesize counter electrode (CE) material used in dye-sensitized solar cells (DSSCs), MoSe 2 nanoflowers (300 ∼ 400 nm) with nanosphere hierarchical architecture were prepared successfully via a facile and economical hydrothermal method. The systematical electrochemical measurements including EIS, CV and Tafel polarization experiments illustrated that MoSe 2 nanoflowers exhibited superior electrocatalytic property. The excellent electrocatalytic performance could be due to abundant active sites, stable chemical property, enhanced exchange current density ( J 0 ) and decreased charge-transfer resistance ( R ct ) of the fabricated MoSe 2 nanoflowers. In addition, the DSSCs assembled by MoSe 2 CE achieved more remarkable photovoltaic performance (PCE = 7.01%) for I 3 − reduction than standard Pt CE (PCE = 6.38%), suggesting that MoSe 2 nanoflowers could be a promising alternative for CE material in DSSCs. [ABSTRACT FROM AUTHOR]

A continuous hydrothermal flow synthesis method was used to produce copper(I) oxide nanoparticles, which were used as an electrocatalyst for the reduction of CO 2 . A rotating ring-disc electrode (RRDE) system was used to study the electroreduction processes, including a systematic study (including quantitative NMR analysis) to identify product species formed at the disc and detected at the ring. In 0.5 M KHCO 3 electrolyte with a pH of 7.1, carbon dioxide was found to be exclusively reduced to formate. In the potential range −0.5 to −0.9 V vs the reversible hydrogen electrode (RHE), an active material/glassy-carbon disc electrode was shown to produce formate, with a maximum Faradaic efficiency of 66% (at −0.8 V vs RHE). [ABSTRACT FROM AUTHOR]

By varying Co:Sb molar ratio, crystalline CoSb 2 O 4 was synthesized through surfactant free hydrothermal method. The tetragonal crystal structure and phase composition of cobalt antimonate were obtained through XRD Rietveld refinement method. CoSb 2 O 4 exhibits a direct band gap of 2.89 eV was computed using First-principle density functional theory (DFT) calculations. Here, the Fermi energy level is upshifted to conduction band region, representing the n-type behaviour of the CoSb 2 O 4 unit cell. The oxidation state of +2 and + 3 of Co was identified through X-ray photoelectron spectroscopy analysis (XPS). Formation of submicron size, rod shape particles was confirmed by Transmission electron microscopic (TEM) images. Cyclic voltammogram exhibits a specific capacitance of 598 F g −1 at 2 mV s −1 in 1 M KOH. More importantly, Galvanostatic charge-discharge analysis (GCD) delivered the specific capacitance of 382 F g −1 at 1 mA cm −2 . For practical application, an asymmetric supercapacitor is constructed using Ni 3 (Fe(CN) 6 ) 2 (H 2 O) as a positive electrode and synthesized one-dimensional CoSb 2 O 4 as a negative electrode, which offered a maximum specific capacitance of 279 Fg -1 at 1 mV s −1 . Cycling stability of the fabricated device demonstrated the retention of almost 100% and hence depicts its promising nature as an efficient electrode for supercapacitor application. [ABSTRACT FROM AUTHOR]

Cobalt sulfide materials are wildly investigated in oxygen evolution reaction (OER). In order to further decrease the cost of the catalysts, cobalt-copper-iron trimetal sulfides (CoCuFe-S) are designed and successfully fabricated via a simple hydrothermal method following a thermal treatment. CoCuFe-S has a three-dimensional nanostructure, which is assembled by numerous nanosheets. Three components are uniformly distributed in the composite. CoCuFe-S with different ratios are employed as OER catalysts and compared with pure Co 9 S 8 , CuS and FeS. The optimal CoCuFe-S-8 catalyst exhibits high and robust activity for OER with a small overpotential of 0.30 V at current density of 10 mA cm −2 and a low Tafel slope of 79 mV·dec −1 . The turnover frequency is 0.27 s −1 and the mass activity is 114 A g −1 at overpotential of 0.30 V, even better than the commercial RuO 2 . In addition, CoCuFe-S-8 catalyst showed long-term durability under 1 M KOH solution. The excellent OER performance may result from the synergistic effect among the three sulfides. The introduction of FeS and CuS are beneficial for the formation of Co 9 S 8 , increasing the conductivity of the catalyst and decreased the adsorption of the oxygen atoms on Co atom. [ABSTRACT FROM AUTHOR]

We report the synthesis, characterization, and performance evaluation of tungsten (W) incorporated vanadium oxide (VO 2 ) nanocomposite cathode material for improved lithium storage performance. VO 2 nanorods, 100–200 nm in diameter and 1–3 μm in length are synthesized using a hydrothermal method. W incorporation at different weight percent results in the VO 2 morphology shifting from rods to a sheet type structure. The lithium storage performance of VO 2 has improved remarkably by increasing the loading of W to an optimal level, which influence the intercalation/ deintercalation of lithium ions into the expanded lattices of VO 2 . The maximum specific capacity observed for the optimal VO 2 /W 4 composite was 381 mAh/g at a current density of 0.1 C. Cyclic voltammetry measurements showed the presence of an electroactive V 3+ /V 4+ redox couple, leading to lower peak separation and voltage polarization differences. Superior charge storage performance was observed with the VO 2 /W 4 composite as compared to the VO 2 based devices. [ABSTRACT FROM AUTHOR]