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Abstract We reported a facile, inexpensive, and high-performance triboelectric nanogenerator (TENG) designed by utilizing the micropatterned polytetrafluoroethylene (MP-PTFE) and aluminum (Al) as triboelectric materials with opposite tendencies. To reduce the fabrication cost as well as to enhance the contact area of PTFE, the micropatterns were formed on its surface by adopting a simple and cost-effective thermal imprinting lithography using sandpapers as a master mold. Consequently, the micropatterns were successfully replicated on the PTFE from the low surface energy sandpaper mold, which does not require any surfactant coating and expensive high vacuum equipment. The proposed TENG device can convert mechanical energy into electricity by continuous contact and separation between the MP-PTFE and Al. The sandpapers with three grit sizes were employed and the effect of average diameter of micropatterns on the electrical output of TENG was analyzed. The MP-PTFE replicated from the sandpaper with a larger grit size can offer a high contact area between the electrodes, thus resulting in the highest electrical output of TENG. Additionally, the effect of external pushing force and load resistance on the output performance of the TENG device was investigated, including the device robustness. Highlights • We reduced the fabrication cost of TENG by employing the sandpaper-assisted MP-PTFE. • MP-PTFE film was developed by TIL technique using commercially available sandpapers. • The MP-PTFE plays a key role in reducing TENG cost and enhancing electrical output. • High and stable electric power generated by TENG is efficient to drive several LEDs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Metal vanadate hydroxides, including mono and binary variants, were synthesized using a one-pot approach. • Ni 0.33 Co 0.67 vanadate hydrate had excellent performance with 373.9 µAh cm−2/140 mAh g−1 and 100,000 cycle life. • Metal content variations resulted in various morphological structures. • The Ni 0.33 Co 0.67 vanadate hydrate was used as the positive electrode to fabricate the ASC. • The designed ASC showed high energy and power densities with 100,000 cycling life. The structural design of electroactive materials including rich profits of high capacitance/capacity and exalted durability is of considerable importance in the development of high-performance wearable energy storage technologies. Herein, a simple and single-step hydrothermal approach is demonstrated to design hierarchical feathers-like microsheet arrays for asymmetric supercapacitors (ASCs) with stable cycling performance. The preparation is carried out at low temperatures without any annealing process, and the as-designed nickel/cobalt vanadate hydrates supported on conductive carbon cloth textile are endowed with the unique architecture of feathers-like microsheets, which allows for the effective contact of active materials, rapid ion diffusion, easy electrolyte penetration, and fast electron transfer. Considering these merits in amalgamation, the Ni 0.33 Co 0.67 vanadate hydrate active material shows a superior areal/specific capacity value of 373.9 µAh cm−2/140 mAh g−1 with outstanding cycling performance (100,000 cycles) than those in the design of mono NiV and CoV hydrates as well as the other fabricated electrode (Ni:Co ratio) materials. Furthermore, the Ni 0.33 Co 0.67 vanadate hydrate active material, when employed as a positive electrode for ASCs, demonstrates excellent electrochemical performance. The assembled ASC exhibits high energy and power density values of 0.19 mWh cm−2 and 2.04 mW cm−2, respectively along with remarkable cycling retention of 82.2% after the completion of 100,000 cycles. Also, the as-assembled device was tested by powering different wearable electronics. This work creates a new pathway for the fabrication of single-step Ni-Co vanadate hydrates for durable electrochemical energy storage applications. [ABSTRACT FROM AUTHOR]

Via a simple and cost-effective one-pot solvothermal synthesis, the highly conductive metal–organic framework-derived binder-free electroactive materials deliver excellent redox reactions and outstanding cycling performance. The optimized electrode is used as the positive electrode to fabricate the electrochemical cell and it exhibits excellent electrochemical properties and cycling stability. [Display omitted] • Ni-Co TH with commercial-level mass loading was prepared by a simple solvothermal method. • The effect of reaction time and temperature on the morphology and electrochemical properties was investigated. • All the prepared Ni-Co TH electrodes revealed ultrahigh areal capacity. • The obtained micro- and nano-structures for optimum electrode showed superior areal capacity. • The fabricated electrochemical cell exhibited outstanding cycling stability. Nowadays, metal–organic framework-derived (MOF-D) materials are auspicious in various research areas due to their beneficial traits of diverse structural features, large surface area, and high porous nature. Herein, we report the MOF-D nickel–cobalt terephthalate hydroxides (Ni-Co THs) via a one-pot solvothermal approach without further annealing. Direct growth of active materials on conductive substrates (e.g., nickel foam (NF)) can potentially eliminate the use of sluggish and non-conductive binders, leading to enhanced redox chemistry with commercial-level mass loading (8–10 mg cm−2). All the binder-free MOF-D Ni-Co TH electrodes demonstrated excellent areal capacities at the same current density of 3 mA cm−2. Among them, the Ni-Co TH-160/9h electrode delivered a superior areal capacity/specific capacity of 2087 µAh cm−2/200.68 mAh g−1 at 3 mA cm−2, together with outstanding cycling retention of 100 % after 20,000 charge–discharge cycles. The achieved ultrahigh performance is ascribed to the synergistic properties of Ni-Co THs, three-dimensional porous NF, and morphological structures. Utilizing the charge storage performance of the Ni-Co TH-160/9h electrode, an electrochemical cell (ECC) was assembled. The as-assembled ECC delivered good areal capacity (1678.6 µAh cm−2), energy density (1.3 mWh cm−2), and power density (48.6 mW cm−2) with outstanding cycling performance (35,000 cycles (99.9 %)). Also, the ECC verified its energy storage properties by powering various portable electronic appliances. [ABSTRACT FROM AUTHOR]

• Hierarchical CoO@CoSe heterostructures were synthesized via a hydrothermal process. • CoO@CoSe composite material was composed of three-dimensional nanoparticles. • The prepared hybrid composite electrodes showed a high electrochemical performance. • Hybrid supercapacitor exhibited high energy and power densities with superior cycling retention. Hierarchical porous structured active materials for energy storage devices could increase the surface area, stimulate the charge transport kinetics, and regulate the volume changes during the charge/discharge process. Moreover, the fabrication of heterostructures would increase the interfacial electric field and modify the electronic structure. The features of hierarchical porous heterostructures are more beneficial to enhance the electrochemical properties and robustness of electrode materials for supercapacitors (SCs). Herein, novel hierarchical lychee fruit-like cobalt-oxide@coblat-selenide heterostructure composites (LF-CoO@CoSe HSCs) composed of three-dimensional nanoparticles were prepared via an efficient single-step hydrothermal approach followed by calcination treatment. The LF-CoO@CoSe HSC-500 electrode exhibited a high specific capacity value of 341.6 mAh g−1 (2146.2 F g−1) at a current density of 2 A g−1 compared to the other electrodes annealed at 400 and 600°C (LF-CoO@CoSe HSC-400 (307.2 mAh g−1) and LF-CoO@CoSe HSC-600 (131.8 mAh g−1)), respectively. The LF-CoO@CoSe HSC-500 electrode delivered good cycling stability (77.5%). Furthermore, the pouch-type aqueous hybrid SC (AHSC) was constructed with LF-CoO@CoSe HSC-500 as a positive electrode and porous activated carbon as a negative electrode. The assembled AHSC device delivered maximum energy and power density values of 37.01 Wh kg−1 and 9490 W kg−1, respectively with superior cycling stability of 134% even after 5000 cycles. Furthermore, the fabricated AHSC device was successfully powered a mini light-emitting diode bulb and a timer display. The prepared composites could be an efficient electro-active material for high-capacity SC applications. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • 3D hierarchical hexagonal plate-like Co 3 O 4 @NF microstructure arrays were directly synthesized via a simple solvothermal process. • The NH 4 F was employed as a template in the preparation of hexagonal plate-like Co 3 O 4 @NF microstructure. • The outstanding capacity values of 500 and 390 mA h g−1 were obtained (Co 3 O 4 @NF-140) at 1 and 2 A g−1, respectively over 500 cycles. • The Co 3 O 4 @NF-140 electrode showed excellent rate capability of 1126 mA h g−1 at 200 mA g−1 after 90 cycles. Three-dimensional (3D) hierarchical hexagonal plate-like Co 3 O 4 microstructure arrays were directly deposited on nickel (Ni) foam via a simple solvothermal process and consequent annealing treatment. The NH 4 F was employed as a template in the preparation of hexagonal plate-like Co 3 O 4 microstructure arrays. The 3D hexagonal plate-like Co 3 O 4 microstructure synthesized at 140 °C (Co 3 O 4 @NF-140) exhibited better morphology compared to the samples obtained at 160 °C (Co 3 O 4 @NF-160) and 180 °C (Co 3 O 4 @NF-180). Remarkably, as-synthesized materials were used as an anode material for lithium (Li)-ion batteries and the optimized electrode (Co 3 O 4 @NF-140) exhibited superior Li storage performance, i.e., noteworthy rate capability and good cycling performance. The outstanding capacity values of 500 and 390 mA h g−1 were obtained at 1 and 2 A g−1, respectively over 500 cycles. Additionally, the specific capacity of the optimized electrode (Co 3 O 4 @NF-140) could retain the 606 mA h g−1 at 500 mA g−1 after 100 cycles with less capacity fading and exhibited excellent rate performance. The superior performance is ascribed to the proficient charge transportation from the 3D hierarchical Co 3 O 4 microstructures to the substrate, improved solid interface with the current collector, and strongly adhered microstructures related to the cyclic charge–discharge process. [ABSTRACT FROM AUTHOR]

The development of three-dimensional (3D) microarchitectures with desirable porous surface morphologies has gained extensive attention in the area of energy storage system due to their superior structural characteristics. The porous morphology consists of high surface area which could be useful for the demonstration of superior energy storage ability to their solid counterpart on account of the easy access of electrolyte ions into the active material. Herein, we designed the 3D flower-like CuCo 2 O 4 and 3D maple leaf-like CuCo 2 O 4 microarchitectures using a facile and nature-friendly oil-bath (silicone oil) process and subsequent calcination in the ambient atmosphere. The prepared CuCo 2 O 4 products revealed 3D flower-like and maple leaf-like microarchitecture morphologies by the exchange of the solvents during synthesis. The synthesized porous materials-based electrodes showed dominant battery-like electrochemical performance in aqueous alkaline media. Interestingly, the 3D maple leaf-like CuCo 2 O 4 microarchitectures exhibited a prominent surface area of 153.33 m2 g−1 which can empower additional electroactive sites to access more electrolyte ions diffused into the electrode and showed a good specific capacity ~302 mA h g−1 at 1 A g−1 with excellent cycling and rate capability. These superior results are achieved due to the unique 3D maple leaf-like morphological shape and its high porous feature from its surface. Moreover, a pouch-type hybrid supercapacitor was constructed and it showed better energy and power density values of 38.54 Wh kg−1 and 7250 W kg−1, respectively. Finally, the fabricated device was tested for practical usage while operating low-power electronics. [ABSTRACT FROM AUTHOR]

To render supercapacitors (SCs) more practical, they must exhibit high cycling stability of at least ten thousand cycles with commercial-level mass loadings, which differentiates them from batteries. Metal-organic framework (MOF)-based electrode materials are promising for use in energy storage systems owing to their excellent electrochemical performance. In this study, we report the electroactivities of bimetallic MOFs (Co, Ni, and Co–Ni) using a single-step, facile, and cost-effective hydro/solvothermal method. To optimize their performances, we develop a general strategy for analyzing various binder-free MOFs. Additionally, the effects of the reaction time, reaction temperature, solvents, and elements (Ni, Co, and H 2 BDC) on the surface morphology and electrochemical performance are investigated. Based on an analysis of the electrochemical properties of all the synthesized electrode materials, the optimal electrode delivers an ultrahigh areal capacity of 2621 µAh cm−2 (297.1 mAh g−1) at 7 mA cm−2, with a high-rate capability of 82.5 % even at 40 mA cm−2. The optimized Co–Ni MOF electrode is employed as a positive electrode to fabricate an aqueous hybrid SC (HSC) with an activated carbon-coated nickel foam electrode as a negative electrode. The as-fabricated HSC exhibits excellent electrochemical properties with exceptional cycling stability (120k cycles) and improved rate capability (60 %). Additionally, we identify factors that contribute to improved redox reactions in the Co–Ni MOF-based HSC, such as the role of Co–Ni MOFs in the redox reaction and the influences of other structural parameters on charge storage and transfer processes. Our aim is to further understand the underlying mechanisms of the improved redox reactions and thus obtain new insights into the design and optimization of Co–Ni MOF-based HSCs. Finally, the energy storage properties of the HSC are validated by using it to power different electronic devices. The promising outcomes obtained in this work can serve as a basis for the future practical implementation of high-energy-density HSCs with high mass loadings and charging rates. To render the practicability of hybrid supercapacitor (HSC) with enhanced energy storage properties, we investigate the electroactivities of bimetallic metal-organic frameworks (MOFs) (Co, Ni, and Co–Ni) using a single-step, facile, and cost-effective hydro/solvothermal method. To optimize their performances, a general strategy is developed for analyzing various binder-free MOFs. Additionally, the effects of the reaction time, reaction temperature, solvents, and elements (Ni, Co, and H 2 BDC) on the surface morphology and electrochemical performance are studied. In addition, we validate the energy storage properties of the HSC by using it to power different electronic devices. The promising outcomes obtained in this study can serve as a basis for the future practical implementation of high-energy-density HSCs with high mass loadings and charging rates. [Display omitted] [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) are gaining much research interest recently owing to their facile and cost‐effective device structure. However, the effect of relative humidity (in moisture atmosphere) on the output performance still needs to be resolved. Herein, a pouch‐type TENG is proposed to significantly reduce the effect of relative humidity on its electrical output and a stable performance is also attained in a humid environment. In this regard, a dielectric and dielectric materials‐based TENG (DD‐TENG) is first developed using nanoarchitecture polydimethylsiloxane (NA‐PDMS) and multiwalled carbon nanotube/nylon composite layers as a triboelectric material with the negative and positive tendencies, respectively. The NA‐PDMS and nylon composite layers play a key role in increasing the surface contact area and surface charge density between the dielectric/triboelectric materials as well as the output performance of DD‐TENG. However, the DD‐TENG device exhibits a stable and high output performance with the effective output power density of ≈25.35 W m−2. Additionally, the performance of the pouch‐type DD‐TENG device is not almost affected even though the relative humidity is increased from 35 to 81%, while it is dramatically decreased for the nonpouch‐type device. Finally, the pouch‐type DD‐TENG is employed as a wearable device to effectively harvest the mechanical energy from daily human activities. [ABSTRACT FROM AUTHOR]

[Display omitted] • The utilization of DHBQ as a mediator in the Mediated fuel cell (MedFC). • The DHBQ reduced in a packed-bed reactor has been fed as an anodic fuel in MedFC. • 1.12 V of open circuit voltage and 282 mW/cm2 power have been obtained in MedFC. Hydrogen fuel cells, which produce electrical energy and only water as a byproduct, are evaluated for their use in eco-friendly technology. However, there are challenges with using abundant precious metal catalysts for electrodes, particularly regarding hydrogen gas crossover and managing the moisture of the polymer electrolyte membrane. To overcome these challenges, a mediated fuel-cell (MedFC) system, in which hydrogen fuel cells are combined with a redox-flow battery using an oxidation–reduction reaction of an electrolyte, has been recently developed. In a MedFC system, the reduced ions of redox-active materials generated by the oxidation of hydrogen in a packed-bed reactor are fed to the fuel cell electrode as a mediator. In this study, 2,5-dihydroxy1,4-benzoquinone (DHBQ) was used as a anode mediator to operate MedFCs under alkaline conditions. DHBQ and hydrogen were injected with an upward flow into the packed-bed reactor to reduce DHBQ via a chemical reaction. On the anode side of the fuel cell, DHBQ oxidized and transferred the electrons to the cathode. By contrast, an oxygen reduction reaction (ORR) occurred at the cathode under alkaline conditions. The reduction potential of DHBQ was −0.72 V (vs. SHE), and that of ORR was 0.4 V (vs. SHE); thus, the theoretical potential of the cell was 1.12 V. During the MedFC operation, a maximum power density of 282 mW/cm2 was obtained. [ABSTRACT FROM AUTHOR]

Green hydrogen, commonly produced through water electrolysis, has attracted considerable attention owing to its energy-efficient and eco-friendly properties. However, since conventional water electrolysis system has fatal drawbacks owing to the high process cost and energy requirements, various approaches are being adopted to increase its energy efficiency. In this study, a novel hybrid system for green hydrogen production was designed by replacing the oxygen evolution reaction (OER) with electrochemical oxidation of catechol (CAT). CAT is an environmental pollutant generated by diverse industries and needs to be further treated because of its toxicity to humans and nature. Accordingly, to facilitate the degradation of CAT and increase the energy efficiency, the pH values of the anolyte (containing CAT) and catholyte were adjusted to alkali and acid, respectively. Two types of ion-exchange membranes (IEMs; anion-/cation-exchange membranes) were coupled to divide the hybrid cell into three compartments, and a buffer solution (NaCl solution) was injected between the IEMs. As a result, the hybrid system output 3.75 mW/cm2 of electricity, spontaneously produced hydrogen with 4.2 mL/h of hydrogen production rate and removed ions from the buffer solution with 0.46 mg/cm2∙min of high desalination rate. A spontaneous green-hydrogen production system with simultaneous desalination of saltwater was suggested using catechol oxidation reaction. This system output 3.75 mA/cm2 of power and spontaneously generated 4.2 mL/h of green hydrogen of constant current at 5 mA/cm2, resulting in a fast desalination rate of 0.46 mg/cm2·min without external energy supply. [Display omitted] • Green hydrogen is produced spontaneously with simultaneous desalination of brine. • Electro-oxidation of catechol is paired with hydrogen evolution reaction. • The spontaneous hybrid system is organized by controlling pH of electrolytes. • 4.2 mL/h of green hydrogen is produced with 0.46 mg/cm2∙min of desalination rate. [ABSTRACT FROM AUTHOR]

Recently, hybrid nanogenerators (HNGs) based on the synergetic piezo/triboelectric effect have shown great promise for attaining high electrical output. In this work, microparticles (MPs) of calcium-doped barium zirconate titanate (Ca-BZT) are synthesized by a solid-state technique and subseqently dispersed into polydimethylsiloxane (PDMS) to prepare a composite film. This composite film is employed to develop an HNG device to efficiently harvest energy from various mechanical motions by individual piezoelectric or triboelectric effects, or a combined synergetic effect. The surface roughness, charge density, and dielectric permittivity of the composite films are significantly enhanced, resulting in an increase in output performance of the HNG device. The effect of Ca doping concentration on the ferroelectric characteristics of the BZT MPs and the output performance of the HNG device are systematically investigated. The BZT MPs with 2 mol% of Ca dopant optimize the high remnant polarization and piezoelectric coefficient of the Ca-BZT/PDMS composite. Moreover, the HNG device with the corresponding composite film also exhibits a maximum electrical output performance, with open-circuit voltage, short-circuit current, and power density values of 550 V, 34 μA, and 23.6 W/m2, respectively. Additionally, the mechanical stability and durability of the HNG device are investigated. To verify the practical applicability of the HNG, the generated output power is employed to demonstrate its ability to harvest biomedical energy and to power several light-emitting diodes as well as portable electronic devices. [ABSTRACT FROM AUTHOR]