A Water Dissolvable Electrolyte with an Ionic Liquid for Eco‐Friendly Electronics

A water‐dissolvable electrolyte is developed by combining an ionic liquid (IL) with poly(vinyl alcohol) (PVA), which decays over time by contact with water. An IL generally consists of two species of ions (anion and cation), and forms an electrical double layer (EDL) of a large electrostatic capacitance due to the ions accumulated in the vicinity of a conductive electrode when voltage is applied. In a similar manner, the ionic gel developed in this work forms an EDL due to the ions suspended in the conjugated polymer network while maintaining the gel form. Test measurements show a large capacitance of 13 µF cm⁻² within the potential window of the IL. The ionic gel shows an electrical conductance of 20 µS cm⁻¹ due to the ionic conduction, which depends on the weight ratio of the IL with respect to the polymer. The developed ionic gel dissolves into water in 16 h. Potential application includes the electrolyte in disposable electronics such as distributed sensors and energy harvesters that are supposed to be harmless to environment.     

Studies on electrical double layer capacitor with a low-viscosity ionic liquid 1-ethyl-3-methylimidazolium tetracyanoborate as electrolyte

The performance of an electrical double layer capacitor (EDLC) composed of high surface area activated carbon electrodes and a new ionic liquid, 1-ethyl-3-methylimidazolium tetracyanoborate, [EMIm]TCB, as the electrolyte has been investigated by impedance spectroscopy, cyclic voltammetry and galvanostatic charge–discharge studies. The high ionic conductivity (~1·3 × 10^???2 S cm^???1 at 20 °C) and low viscosity (~22 cP) of the ionic liquid, [EMIm]TCB, make it attractive as electrolyte for its use in EDLCs. The optimum capacitance value of 195·5 F g^???1 of activated carbon has been achieved with stable cyclic performance.     

Synthesis and optimization of P(MMA-BA-MAA)/PEG-based polymer gel electrolytes

A polymer gel electrolyte based on poly(methyl methacrylate-butyl acrylate-methacrylic acid)/polyethylene glycol 400 blend (P(MMA-BA-MAA)/PEG400) was successfully prepared by a simple and efficient procedure. The optimal ionic conductivity was achieved to be 3.12 mS cm^?1 at the temperature of 30 °C when the electrolyte has the composition of 20 wt% P(MMA-BA-MAA)/PEG400 blend, 0.6 M NaI, and 0.06 M I₂ in the solvent γ-butyrolactone (GBL). For tuning the ionic conductivity, various additives were introduced into the polymer gel electrolytes. The measured values of open circuit voltage, short circuit current, and total photovoltaic efficiency indicates that the adding of pyridine (PY) leads to better performance of the final dye-sensitized solar cells (DSSCs), while the adding of Guanidine thiocyante (GuSCN) leads to a worse one. 4-Tert-butylpyridine (TBP) additive takes a more complex effect on the performance of the final DSSCs. For polymer gel electrolyte with 0.5 M pyridine, the final fabricated dye-sensitized solar cell has overall energy conversion efficiency (η) of 3.63 % (0.16 cm² active area) under AM 1.5 at irradiation of 100 mW cm^?2, which reached the level of the liquid electrolyte based device (η = 3.83 % at 0.16 cm² active area). Meanwhile, this gel electrolyte exhibits well long-term stability. The mechanism analysis revealed the dependences of ionic conductivity on the concentration of polymer and NaI and the temperatures.     

Solution blown aligned carbon nanofiber yarn as supercapacitor electrode

Carbon materials with various microtextures and wide availabilities represent very attractive electrode materials for supercapacitors. In this paper, a modified solution blowing process, using a pair of parallel rods as collector, was reported to fabricate carbon nanofiber yarn (CNFY) with polyacrylonitrile (PAN) as precursor polymer. The morphology and structure of the nanofibers were investigated. The PAN precursor and carbon nanofibers were well-aligned and their average diameter was 280 nm and 187 nm, respectively. The performance of CNFY as supercapacitor electrode was evaluated. The CNFY possessed high conductivity of 608.7 Scm^?1 and mass specific capacitance of 70 Fg^?1 at the current density of 500 mAg^?1, and the reduction of capacitance is 29.14 % of the initial value at the current density range from 0.5 to 8 Ag^?1. The superior performance of the CNFY electrode was attributed to the well-aligned structure and high electrical conductivity which afforded the potential application as a novel electrode for supercapacitors.     

Synthesis and characterization of nanotree-like polyaniline electrode material for supercapacitors

In this work, polyamidoamine (PAMAM) dendrimers are used as templates to synthesize nanotree-like polyaniline (PANI) materials, which are further used as electrode materials for supercapacitors. Effects of PAMAM content on PANIs’ structural characteristics and electrochemical properties are investigated detailedly. SEM images show that at 0.1 % PAMAM content, the PANI presents a stable self-assembled dendritic structure composed of many nanorods. Compared with pure PANI, nanotree-like PANI has better crystallinity, higher doping degree, larger high surface area and better reactivity. At a current density of 1 A g^?1, the PANI nanotree electrode displays a high specific capacitance value of 812 F g^?1, which is 119 % higher than that of pure PANI. Even after 1000 cycles, it still maintains about 69 % of the initial capacitance, showing good electrochemical stability. Thus the PANIs with nanotree structures are promising electrode materials for high-performance electrical energy storage devices. Moreover, the possible electrochemical enhancement mechanism of PANI nanotree electrode for supercapacitor is also discussed.     

Electroactive Ionic Soft Actuators with Monolithically Integrated Gold Nanocomposite Electrodes

Electroactive ionic gel/metal nanocomposites are produced by implanting supersonically accelerated neutral gold nanoparticles into a novel chemically crosslinked ion conductive soft polymer. The ionic gel consists of chemically crosslinked poly(acrylic acid) and polyacrylonitrile networks, blended with halloysite nanoclays and imidazolium‐based ionic liquid. The material exhibits mechanical properties similar to that of elastomers (Young's modulus ≈ 0.35 MPa) together with high ionic conductivity. The fabrication of thin (≈100 nm thick) nanostructured compliant electrodes by means of supersonic cluster beam implantation (SCBI) does not significantly alter the mechanical properties of the soft polymer and provides controlled electrical properties and large surface area for ions storage. SCBI is cost effective and suitable for the scaleup manufacturing of electroactive soft actuators. This study reports the high‐strain electromechanical actuation performance of the novel ionic gel/metal nanocomposites in a low‐voltage regime (from 0.1 to 5 V), with long‐term stability up to 76 000 cycles with no electrode delamination or deterioration. The observed behavior is due to both the intrinsic features of the ionic gel (elasticity and ionic transport capability) and the electrical and morphological features of the electrodes, providing low specific resistance (<100 Ω cm^?2), high electrochemical capacitance (≈mF g^?1), and minimal mechanical stress at the polymer/metal composite interface upon deformation.     

Application of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate in polymer heterojunction solar cells

In this study, p-type semiconducting polymer of acid, poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS), has been employed as a hole-transporting electrode to fabricate organic polymer heterojunction photovoltaic cells. The results showed that the resultant poly(3-hexylthiophene): C₆₀ derivatives [6]-phenyl-C₆₁-butyric acid methyl ester (P3HT:PCBM)/PEDOT:PSS can significantly expand the light absorption range which was expected to enhance the sunlight excitation. The influences of annealing conditions and barrier layer on the photoelectric performances were investigated in detail, giving an optimized synthesis conditions: annealed temperature was at 120 °C for 90 min, the thickness of PEDOT:PSS film was approximately 3–4 μm, and the ratio of PCBM and P3HT was 1:2. The blended heterojunction consisting of PCBM and P3HT was used as charge carrier-transferring medium to replace I₃ ^?/I^? redox electrolyte, showing a short-circuit current of 4.30 mA cm^?2, an open-circuit voltage of 0.83 V, and a light-to-electric energy conversion efficiency of 2.37 % under a simulated solar light irradiation of 100 mW cm^?2. In addition, a solid-state polymer heterojunction photovoltaic cells with a short-circuit current of 3.59 mA cm^?2, an open-circuit voltage of 0.80 V, and a light-to-electric energy conversion efficiency of 1.9 % was successfully fabricated by simplifying the process.     

A facile synthetic method and electrochemical performances of nickel oxide/carbon fibers composites

The uniform and completed nanofilms of nickel oxide (NiO) were electrodeposited on the carbon fibers (CFs) by a facile method of cyclic voltammetric. The as-prepared NiO/CFs composites can be used as a flexible electrode for electrochemical supercapacitors. Electrochemical measurements showed that 1.0-NiO/CFs had a good redox process and reversibility, and displayed the specific capacitances as high as 929 F g^?1 at a current density of 1 A g^?1. After 5000 cycles of charge and discharge, the 1.0-NiO/CFs composite materials could retain more than 88% of initial capacitance and show an excellent cyclability. Meanwhile, this supercapacitor exhibited a higher energy density of 20.8 Wh kg^?1 at a power density of 200 W kg^?1. The carbon fibers acting as active substrate for the composite electrode are a good conductor and have a larger capacitance of electrical double layer. The nanofilm structure of NiO could facilitate the contact of the electrolyte with the active materials, thus increasing the Faradaic pseudo-capacitance.     

Synergistic Solar-Driven Freshwater Generation and Electricity Output Empowered by Wafer-Scale Nanostructured Silicon

Electricity generation triggered by the ubiquitous water evaporation process provides an intriguing way to harvest energy from water. Meanwhile, natural water evaporation is also a fundamental way to obtain fresh water for human beings. Here, a wafer-scale nanostructured silicon-based device that takes advantage of its well-aligned configuration that simultaneously realizes solar steam generation (SSG) for freshwater collection and hydrovoltaic effect generation for electricity output is developed. An ingenious porous, black carbon nanotube fabric (CNF) electrode endows the device with sustainable water self-pumping capability, excellent durable conductivity, and intense solar spectrum harvesting. A combined device based on the CNF electrode integrated with nanostructured silicon nanowire arrays (SiNWs) provided an aligned numerous surface-to-volume water evaporation interface that enables a recorded continuous short-circuit current 8.65 mA and a water evaporation rate of 1.31 kg m⁻² h⁻¹ under one sun illumination. Such wafer-scale SiNWs-based SSG and hydrovoltaic integration devices would unchain the bottleneck of the weak and discontinuous electrical output of hydrovoltaic devices, which inspires other sorts of semiconductor-based hydrovoltaic device designs to target superior performance.     

Synthesis and electrochemical performances of a novel two-dimensional nanocomposite: polyaniline-coated laponite nanosheets

A novel two-dimensional nanocomposite, polyaniline-coated laponite (polyaniline/laponite) nanosheets, has been prepared by in situ oxidative polymerization of aniline on the surface of laponite nanosheets. These sheets present a loosely stacked structure with the formation of a great number of pores, which it can provide a larger electrode/electrolyte contact surface area, shorten the path for ions transport in the active material, and alleviate the expansion and contraction of the electrode material during the charge/discharge processes, leading to an improved electrochemical performance. As an active material for supercapacitors, the specific charge/discharge capacitance of polyaniline/laponite nanosheets is 375 and 330 F g^?1 (based on the total working electrode mass) at a current density of 0.5 A g^?1, respectively, with a coulombic efficiency of 88 % which is higher than that of pure polyaniline (28 %). Moreover, polyaniline/laponite nanosheets also show a good rate capability with a growth of current density from 0.5 to 30 A g^?1, a specific discharge capacitance of 266 F g^?1 remained at 30 A g^?1. This work suggests a strategy to improve the electrochemical performances of polyaniline.     

High-Output Single-Electrode Droplet Triboelectric Nanogenerator Based on Asymmetrical Distribution Electrostatic Induction Enhancement

Droplet-based triboelectric nanogenerators (D-TENGs) have recently gained much attention due to their great potential in harvesting energy. However, the output performance of conventional single-electrode droplet-based TENGs is limited owing to low induced electrification efficiency. The asymmetric distribution of electric fields on both sides of the electrode edge enhances the electrostatic induction process and improves the output performance of D-TENG. Herein, an induced electrification-enhanced droplet-based triboelectric nanogenerator (IED-TENG) is developed to effectively enhance the output performance by simultaneously optimizing the electrode structure and the dynamics of the water droplet. One droplet falling from a height of 30 cm results in a −70 V output voltage and −6 µA short-circuit current, which is 70 times and 20 times the full-inductive-electrode mode, respectively. The working principle and the relationship between electric signal and droplet dynamics are analyzed in detail. Moreover, the peak output voltage can reach −110 V, and the peak current can get −140 µA by using the power generation of multiple water droplets. The present protocol provides an easy and reproducibility strategy in energy harvesting and sensing areas.     

Water-promoted zeolitic imidazolate framework-67 transformation to Ni–Co layered double hydroxide hollow microsphere for supercapacitor electrode material

Hollow Ni–Co layered double hydroxide (LDH) was synthesized with rhombic dodecahedral zeolitic imidazolate framework-67 (ZIF-67) as self-sacrificed template and cobalt precursor. Water was found to be very important role on the formation of Ni–Co LDH hollow microstructure. As a supercapacitor electrode material, the obtained hollow Ni–Co LDH delivered a high specific capacitance of 1530 F g^?1 at the current density of 1.0 A g^?1 and good cycle performance, which can be ascribed to its hollow mesoporous structure composed of the Ni–Co LDH nanosheets and high specific surface area. Combined with the AC negative electrodes, the assembled asymmetric supercapacitors performed an energy density of 27.5 Wh kg^?1 at the power density of 375 W kg^?1.     

Super-Aerophilic Biomimetic Cactus for Underwater Dispersed Microbubble Capture,Self-Transport,Coalescence, and Energy Harvesting

Human ocean activities are inseparable from the supply of energy. The energy contained in the gas-phase components dispersed in seawater is a potential universal energy source for eupelagic or deep-sea equipment. However, the low energy density of bubbles dispersed in water introduces severe challenges to the potential energy harvesting of gas-phase components. Here, a super-aerophilic biomimetic cactus is developed for underwater dispersive microbubble capture and energy harvesting. The bubbles captured by the super-aerophilic biomimetic cactus spines, driven by the surface tension and liquid pressure, undergo automatic transport, coalescence, accumulation, and concentrated release. The formerly unavailable low-density dispersive surface free energy of the bubbles is converted into high-density concentrated gas buoyancy potential energy, thereby providing an energy source for underwater in situ electricity generation. Experiments show a continuous process of microbubble capture by the biomimetic cactus and demonstrate a 22.76-times increase in output power and a 3.56-times enhancement in electrical energy production compared with a conventional bubble energy harvesting device. The output energy density is 3.64 times that of the existing bubble energy generator. This work provides a novel approach for dispersive gas-phase potential energy harvesting in seawater, opening up promising prospects for wide-area in situ energy supply in underwater environments.     

Selective electrochemical detection of dopamine based on molecularly imprinted poly(5-amino 8-hydroxy quinoline) immobilized reduced graphene oxide

The dopamine-imprinted conducting polymer film of 5-amino 8-hydroxy quinoline (AHQ) was electrodeposited on reduced graphene oxide (rGO)-modified glassy carbon (GC) electrode and was applied as a molecular recognition element for the selective determination of dopamine. The molecularly imprinted polymer (MIP)-modified electrode showed an excellent affinity towards dopamine due to the presence of imprinted site through hydrogen bonding interaction between dopamine and poly (AHQ) membrane. The molecular recognition ability of MIP-modified electrode was analyzed by cyclic voltammetric and differential pulse voltammetric techniques. The most stable geometry of the template–monomer complex in the pre-polymerization mixture was calculated by computational approaches. The rGO modification augmented both surface area and electron transfer kinetics of the bare electrode. The GC/rGO/MIP electrode possessed 2.83 fold current enhancements when compared to GC/MIP electrode, indicating the improvement in sensitivity due to rGO modification. The limit of detection and sensitivity of GC/rGO/MIP electrode was observed to be 32.7 nM and 13.3 AM^?1 cm^?2, respectively. The imprinting methodology provided an exceptional selectivity towards the detection of dopamine even in the presence of high concentration of possible physiological interferents. Moreover, the fabricated electrode was successfully employed for the detection of dopamine in human blood plasma samples proving the effectiveness of the sensor for the sensitive detection of dopamine from real samples.     

Preparation and characterization of segmented stacking for thermoelectric power generation

Based on the Seebeck effect, thermoelectric generators can convert thermal energy directly into electrical power, which can be applied in waste heat recovery and clean energy generation. In this work, segmented thermoelectric legs were prepared with high-performance thermoelectric materials for the fabrication of multistage thermoelectric generators, which can be utilized in medium temperature energy harvesting. The P-type leg material was Pb_0.94Sr_0.04Na_0.02Te/Bi_0.5Sb_1.5Te₃, and the N-type leg material was Pb_0.94Ag_0.01La_0.05Te/Bi₂Te₃. The length ratio of the two segments was optimized based on the energy conversion efficiency under different working conditions. The segmented legs were measured with the four-probe method at different temperatures to evaluate their output performance. At a temperature difference of 420 K, the maximum output power density was 0.40 W/cm² for the P-type leg and 0.32 W/cm² for the N-type leg.     

Single‐Crystalline,Metallic TiC Nanowires for Highly Robust and Wide‐Temperature Electrochemical Energy Storage

Customized electrode materials with good temperature adaptability and high‐rate capability are critical to the development of wide‐temperature power sources. Herein, high‐quality TiC nanowires are uniformly grown on flexible carbon cloth as free‐standing electric‐double‐layer supercapacitor electrode. The TiC nanowires, 20–40 nm wide and 3–6 µm long, are single‐crystalline and highly conductive that is close to typical metal. Symmetric supercapacitors are constructed with ionic liquid electrolyte and TiC nanowires electrodes as wide‐temperature and long‐cycle stable power source. Ultrastable high‐rate cycling life of TiC nanowire arrays electrodes is demonstrated with capacitance retention of 96.8% at 60 °C (≈440 F g^?1), 99% at 25 °C (≈400 F g^?1), and 98% at ?25 °C (≈240 F g^?1) after 50 000 cycles at 10 A g^?1. Moreover, due to high electrical conductivity, the TiC nanowire arrays show ultrafast energy release with a fast response time constant of ≈0.7 ms. The results demonstrate the viability of metal carbide nanostructures as wide‐temperature, robust electrode materials for high‐rate and ultrastable supercapacitors.     

Cross-Link-Dependent Ionogel-Based Triboelectric Nanogenerators with Slippery and Antireflective Properties

Given the ability to convert various ambient unused mechanical energies into useful electricity, triboelectric nanogenerators (TENGs) are gaining interest since their inception. Recently, ionogel-based TENGs (I-TENGs) have attracted increasing attention because of their excellent thermal stability and adjustable ionic conductivity. However, previous studies on ionogels mainly pursued the device performance or applications under harsh conditions, whereas few have investigated the structure–property relationships of components to performance. The results indicate that the ionogel formulation—composed of a crosslinking monomer with an ionic liquid—affects the conductivity of the ionogel by modulating the cross-link density. In addition, the ratio of cross-linker to ionic liquid is important to ensure the formation of efficient charge channels, yet increasing ionic liquid content delivers diminishing returns. The ionogels are then used in I-TENGs to harvest water droplet energy and the performance is correlated to the ionogels structure–property relationships. Improvement of the energy harvesting is further explored by the introduction of surface polymer brushes on I-TENGs via a facile and universal method, which enhances droplet sliding by means of ideal surface contact angle hysteresis and improves its anti-reflective properties by employing the I-TENG as a surface covering for solar cells.     

Estimating the energy of electric breakdown in air gap between electrolyte and metal electrode

The influence of induced electric charge (localized on the surface of a suspended copper rod) on the formation of a protrusion (Taylor cone) on the inducing liquid (aqueous solution) surface is considered. At an applied voltage of U ≤ 12 kV, the protrusion height in the interval of pre-breakdown voltages (U < U _P) is limited by the electric field strength. At U > U _P, the growth of protrusion is terminated by an electric discharge, which drives the liquid to oscillate in a broad range of applied voltages U at almost constant multiple frequencies f = f ₀ n, which are resonantly switched at certain fixed U values. By measuring the amount of evaporated liquid, the energy (27.8 × 10⁻³ J) and current (64.9 A) of single discharge were evaluated and the electric capacitance (7.6 × 10⁻¹⁰ F) of a system comprising the water surface and suspended copper electrode was estimated. Serial connection of an additional capacitor (100 μF) to the copper electrode with induced electric charge leads to a threefold increase in these parameters.     

Nitrogen-doping hierarchically porous carbon nanosheets for supercapacitor

Two-dimensional (2D) porous carbon nanosheets attract great attention because of their thin sheet-like morphology, abundant pores and high specific surface area, and their potential applicability in many fields including adsorption, oxygen reduction reaction, organic transistor and energy storage. Herein, a feasible method, named self-templating, to prepare 2D nitrogen-doping hierarchically porous carbon nanosheets (N-HPCNs) with prominent performances as supercapacitor electrode is reported. During the process of preparation, the inexpensive and easily available MgO rods are treated in water to form Mg(OH)₂ nanosheets further using as templates and then nitrogen contained resorcinol–formaldehyde resin oligomers as carbon and nitrogen precursor co-condense onto the templates by electrostatic interaction. The obtained N-HPCNs with large specific surface area, hierarchical pores and unique interconnected sheet-like structure are the potential candidates for high energy storage devices. As an active electrode material for electrochemical double-layer capacitors, N-HPCNs exhibit a capacitance of 201 F g^?1 at current density of 1 A g^?1 and high specific capacitance (78.1% retention of initial capacitance even at 10 A g^?1), with excellent cycling life stability (3.5% loss after 5000 cycles).     

Effect of different copper fillers on the electrical resistivity of conductive adhesives

The effects of different copper fillers with different morphology and particle size have been studied in terms of electrical resistivity and thermal stability on the electrically conductive adhesives. The copper fillers used in this study were prepared by wet chemical reduction, electrolytic and gas atomization method, respectively. The as cured ECAs filled with different type of Cu fillers showed significant difference in electrical resistivity. Cu filler with smaller particle size showed higher packing density and larger surface area, which would enhance formation of conductive channels and increased conductive network in the ECAs, leading to a lower electrical resistivity. In addition, thermal stability of the ECAs were investigated under high temperature exposure at 125 °C and high humidity aging at 85 °C/85% RH for 1,000 h. Results showed that ECAs with Cu fillers of relatively small particle size and rough particle surface have excellent thermal stability due to enhanced adhesion and contact area between Cu fillers and the polymer matrix. A very low resistivity at an order of magnitude of 10^?4 ?? cm could be maintained for these ECAs after 1,000 h at 125 and 85 °C/85% RH.