Enhancing the Output Performance of Triboelectric Nanogenerator via Grating‐Electrode‐Enabled Surface Plasmon Excitation

The surface charge density and the output impedance of triboelectric nanogenerators (TENGs) are two critical factors for TENGs to speed up their commercialization, so it is important to explore unique methods to reduce the output impedance and increase the surface charge density. Here, an approach is demonstrated to effectively boost the output performance of TENG while reducing the output impedance of TENGs by utilizing grating‐electrode‐enabled surface plasmon excitation. A sustainable and enhanced output performance of about 40 µA (short‐circuit current) and 350 V (peak‐to‐peak voltage at a resistance of 10 MΩ) is produced via grating‐coupled surface plasmon resonance on the TENG with the aluminum grating electrode in the line density of 600 lines mm^?1, and it delivers a peak output power of 3.6 mW under a loading resistance of 1 MΩ, giving over 4.5‐fold enhancement in output power and a 75% reduction in the output impedance. Finally a self‐powered ultrasonic ranging system is utilized to verify the capability of the TENG in powering portable electrics.     

A Universal Strategy for Improving the Energy Transmission Efficiency and Load Power of Triboelectric Nanogenerators

Triboelectric nanogenerators (TENGs) have recently been invented as a potential energy technology for harvesting low‐frequency mechanical energy. The load power acquired from a TENG is far less than the maximum output power of the TENG for the large internal impedance and impedance mismatch, and this difference results in an extremely low energy transmission efficiency. Here, a universal strategy is proposed for improving the energy transmission efficiency and load power through dielectric material design, including a reduction in the effective thickness and the directional alignment of the electric dipole. This strategy reduces the internal impedances of TENGs with different modes and results in the improvement of energy transmission efficiency and load power. According to this strategy, the internal impedance of an as‐fabricated TENG is reduced from 16 to 1.3 MΩ, and the energy transmission efficiency is enhanced from 22.46% to 99.5%. Moreover, the load power under 1 MΩ resistance is improved from 0.014 to 0.251 µW, an increase of 18 times. The strategy not only opens a universal and new road to power management, but also paves the way for the industrial applications of TENGs.     

Boosting the Charge Density of Triboelectric Nanogenerator by Suppressing Air Breakdown and Dielectric Charge Leakage

Charge generation and charge decay are two essential factors that determine the surface charge density of a triboelectric nanogenerator (TENG). However, research mainly focuses on boosting charge generation, and little attention is paid to suppressing charge decay. Here, a strategy of suppressing charge decay, including the air breakdown and dielectric charge leakage, of TENG with high surface charge density (HCD-TENG) is proposed by utilizing a dual dielectric layer. A series of parameters of different dielectric materials are tested with the assistance of a charge excitation TENG (CE-TENG) to reveal the relationships between charge generation, air breakdown, and dielectric charge leakage in the atmospheric environment. Further, the phenomenon of dielectric charge leakage limiting the maximum output of TENG prior to air breakdown is observed for the first time. With the simultaneous suppression of the air breakdown and dielectric charge leakage, the output of TENG is enhanced to 2.2 mC m⁻². This work not only provides new insight into the performance optimization and material selection of TENG, but also provides significant guidance for obtaining high-output TENG in the future.     

Long‐Lifetime Triboelectric Nanogenerator Operated in Conjunction Modes and Low Crest Factor

The high‐output triboelectric nanogenerator (TENG) is indispensable for its practical applications toward industrial products. However, the electricity loss in simple parallel connection among all units and the typically high crest factor output seriously hamper the practical applications of TENG. Here, a rectified TENG is reported in parallel structure to solve the problem of electricity loss in simple parallel connection. The rotational contact–separation structure with phase difference between rectified TENGs addresses high crest factor output and extends service life of rotational TENG simultaneously. The current crest factor is dramatically decreased to 1.31 in multiple rectifier multiple TENG in parallel (MRM‐TENG), while that of TENG in simple parallel is higher than 6. Meanwhile, the current output can retain up to ≈93% of its initial performance after 7 200 000 rotations under 2.00 r s^?1 of 1000 h. Furthermore, the equivalent current can be in linear growth with low crest factor by making MRM‐TENG in parallel for distributed energy supply without electricity loss. This work may provide a new strategy for TENG in parallel to achieve a low crest factor output and long‐term cycling stability power generation in distributed energy harvesting for large‐scale power application.     

Self‐Powered Wireless Sensor Node Enabled by a Duck‐Shaped Triboelectric Nanogenerator for Harvesting Water Wave Energy

This paper presents a fully enclosed duck‐shaped triboelectric nanogenerator (TENG) for effectively scavenging energy from random and low‐frequency water waves. The design of the TENG incorporates the freestanding rolling mode and the pitch motion of a duck‐shaped structure generated by incident waves. By investigating the material and structural features, a unit of the TENG device is successfully designed. Furthermore, a hybrid system is constructed using three units of the TENG device. The hybrid system achieves an instantaneous peak current of 65.5 µA with an instantaneous output power density of up to 1.366 W m^?2. Following the design, a fluid–solid interaction analysis is carried out on one duck‐shaped TENG to understand the dynamic behavior, mechanical efficiency, and stability of the device under various water wave conditions. In addition, the hybrid system is experimentally tested to enable a commercial wireless temperature sensor node. In summary, the unique duck‐shaped TENG shows a simple, cost‐effective, environmentally friendly, light‐weight, and highly stable system. The newly designed TENG is promising for building a network of generators to harvest existing blue energy in oceans, lakes, and rivers.     

Boost the Performance of Triboelectric Nanogenerators through Circuit Oscillation

Triboelectric nanogenerator (TENG) which harvests ubiquitous ambient mechanical energy is a promising power source that can meet the distributed energy demand in the internet of things, wearable electronics, etc. However, the available output of TENG is severely limited by the saturated polarized charge density, small intrinsic capacitance, and large matching impedance. Herein, an effective power management strategy is proposed that flips the free charges on the conductive layer through a controlled LC oscillating circuit composed of the diode, switch, inductor, and the intrinsic capacitor of TENG. In this way, the equivalent charge density reaches a level higher than the saturated polarized charge density. The simulation and experiments show that the limit of energy output can be exceeded under arbitrary load resistance, especially for the low‐impedance common electronics. It is believed that such a general, low‐cost, and highly effective strategy can further broaden the applications of TENG devices across the fields and probably be a new performance evaluation standard for TENG.     

Energy Harvesting from Breeze Wind (0.7–6 m s−1) Using Ultra‐Stretchable Triboelectric Nanogenerator

Wind is one of the most important sources of green energy, but the current technology for harvesting wind energy is only effective when the wind speed is beyond 3.5–4.0 m s^?1. This is mainly due to the limitation that the electromagnetic generator works best at high frequency. This means that light breezes cannot reach the wind velocity threshold of current wind turbines. Here, a high‐performance triboelectric nanogenerator (TENG) for efficiently harvesting energy from an ambient gentle wind, especially for speeds below 3 m s^?1 is reported, by taking advantage of the relative high efficiency of TENGs at low‐frequency. Attributed to the multiplied‐frequency vibration of ultra‐stretchable and perforated electrodes, an average output of 20 mW m^?3 can be achieved with inlet wind speed of 0.7 m s^?1, while an average energy conversion efficiency of 7.8% at wind speed of 2.5 m s^?1 is reached. A self‐charging power package is developed and the applicability of the TENG in various light breezes is demonstrated. This work demonstrates the advantages of TENG technology for breeze energy exploitation and proposes an effective supplementary approach for current employed wind turbines and micro energy structure.     

Capacitor‐Integrated Triboelectric Nanogenerator Based on Metal–Metal Contact for Current Amplification

The electrical power of triboelectric nanogenerators (TENGs) is increased by surface modifications, and they can successfully power portable devices alone. However, modifying the material and its surface may limit the device lifetime, and most of the portable applications demonstrated in previous studies have excessive input conditions. In this study, a capacitor‐integrated TENG (CI‐TENG) that uses the fundamental mechanisms of the Leyden jar is developed. In this device, a long sheet metal (capacitor electrode)–polymer–metal composite (TENG electrode) is rolled inside the casing cylinder, and a capacitor unit is fabricated at the end of the sheet composite. This new operating mechanism of the CI‐TENG is analyzed in terms of the dielectric constant of the capacitor unit and the metal‐to‐metal contact between electrodes. By instantaneous charging and discharging of the capacitor unit inside the CI‐TENG, it can generate a peak open‐circuit voltage of 156 V and a peak closed‐circuit current of 4.3 mA under manual input. It charges a capacitor more than three times faster than a conventional TENG does. Furthermore, the internal impedance of the CI‐TENG is decreased to 200 kΩ without any external circuit.     

Ion‐Enhanced Field Emission Triboelectric Nanogenerator

As interest in triboelectric nanogenerators (TENGs) continues to increase, some studies have reported that certain limitations exist in TENG due to high potential difference, resulting in air breakdown and field emission. In addition, with known limitations such as extremely low voltage at low external resistance, a breakthrough is required to overcome the limitations of TENG. Here, a new TENG mechanism is reported, utilizing ion‐enhanced field emission (IEFE). Using a simple IEFE‐inducing layer, which consists of a charge accumulation layer and a metal‐to‐metal contact point, electrons can flow directly to a counter electrode while generating high‐output power. Under vertical contact–separation input, the generated root mean square (RMS) power of IEFE‐TENG is 635% higher compared to conventional TENG. As the fundamental mechanism of the IEFE‐TENG is based on installing this simple IEFE‐inducing layer, the power output of existing TENGs including sliding mode types can be boosted. This new TENG mechanism can be a new standard for metal–metal contact TENGs to effectively amplify the output power and to overcome potential limitations.     

Electrolytes toward High‐Voltage Na3V2(PO4)2F3 Positive Electrode Durable against Temperature Variation

High power and energy density, long cyclability, and tolerance for wide temperature (seasonal and daily operational temperature differences) must be considered to construct large‐scale sodium secondary batteries. In this regard, Na₃V₂(PO₄)₂F₃ (NVPF) has become a subject of interest as a high‐performance positive electrode material owing to its high energy density. However, the high operating voltage of NVPF causes continuous decomposition of electrolytes during cycles, resulting in significant capacity fading and low Coulombic efficiency. In this study, the electrochemical performance of the NVPF electrode in organic solvent electrolytes with and without additives and an ionic liquid is investigated at high voltage regimes over a wide temperature range (?20 °C to 90 °C). The results reveal that the performance of organic electrolytes is still insufficient even with additives, and the ionic liquid electrolyte demonstrates high electrochemical stability and cyclability with NVPF electrodes over a temperature range from ?20 °C to 90 °C, achieving stable cycling over 500 cycles. The detailed electrochemical analysis combined with X‐ray photoelectron and energy dispersive X‐ray spectroscopy indicates that a sturdy cathode electrolyte interphase layer around the electrode protects it from capacity fading at high voltage and elevated temperature, resulting in high Coulombic efficiency.     

In-Situ Constructuring of Copper-Doped Bismuth Catalyst for Highly Efficient CO2 Electrolysis to Formate in Ampere-Level

CO₂ electrochemical reduction (CO₂RR) can mitigate environmental issues while providing valuable products, yet challenging in activity, selectivity, and stability. Here, a CuS-Bi₂S₃ heterojunction precursor is reported that can in situ reconstruct to Cu-doped Bismuth (CDB) electrocatalyst during CO₂RR. The CDB exhibits an industrial-compatible current density of −1.1 A cm⁻² and a record-high formate formation rate of 21.0 mmol h⁻¹ cm⁻² at −0.86 V versus the reversible hydrogen electrode toward CO₂RR to formate, dramatically outperforming currently reported catalysts. Importantly, the ultrawide potential region of 1050 mV with high formate Faradaic efficiency of over 90% and superior long-term stability for more than 100 h at −400 mA cm⁻² can also be realized. Experimental and theoretical studies reveal that the remarkable CO₂RR performance of CDB results from the doping effect of Cu which optimizes adsorption of the *OCHO and boosts the structural stability of metallic bismuth catalyst. This study provides valuable inspiration for the design of element-doping electrocatalysts to enhance catalytic activity and durability.     

Tribovoltaic Effect on Metal–Semiconductor Interface for Direct‐Current Low‐Impedance Triboelectric Nanogenerators

The triboelectric nanogenerator (TENG) is a new energy technology that is enabled by coupled contact electrification and electrostatic induction. The conventional TENGs are usually based on organic polymer insulator materials, which have the limitations and disadvantages of high impedance and alternating output current. Here, a tribovoltaic effect based metal–semiconductor direct‐current triboelectric nanogenerator (MSDC‐TENG) is reported. The tribovoltaic effect is facilitated by direct voltage and current by rubbing a metal/semiconductor on another semiconductor. The frictional energy released by the forming atomic bonds excites nonequilibrium carriers, which are directionally separated to form a current under the built‐in electric field. The continuous average open‐circuit voltage (10–20 mV), short‐circuit direct‐current output (10–20 µA), and low impedance characteristic (0.55–5 kΩ) of the MSDC‐TENG can be observed during relative sliding of the metal and silicon. The working parameters are systematically studied for electric output and impedance characteristics. The results reveal that faster velocity, larger pressure, and smaller area can improve the maximum power density. The internal resistance is mainly determined by the velocity and the electrical resistance of semiconductor. This work not only expands the material candidates of TENGs from organic polymers to semiconductors, but also demonstrates a tribovoltaic effect based electric energy conversion mechanism.     

Improving phosphate buffer-free cathode performance of microbial fuel cell based on biological nitrification

To reduce the amount of phosphate buffer currently used in Microbial Fuel Cell's (MFC's), we investigated the role of biological nitrification at the cathode in the absence of phosphate buffer. The addition of a nitrifying mixed consortia (NMC) to the cathode compartment and increasing ammonium concentration in the catholyte resulted in an increase of cell voltage from 0.3 V to 0.567 V (external resistance of 100 Ω) and a decrease of catholyte pH from 8.8 to 7.05. A large fraction of ammonium was oxidized to nitrite, as indicated by an increase of nitrate-nitrogen (NO₃⁻–N). An MFC inoculated with an NMC and supplied with 94.2 mgN/l ammonium to the catholyte could generate a maximum power of 2.1 ± 0.14 mW (10.94 ± 0.73 W/m³). This compared favorably to an MFC supplied with either buffered or non-buffered solution. The buffer-free NMC inoculated cathodic chamber showed the smallest polarization resistance, suggesting that nitrification resulted in improved cathode performance. The improved performances of the phosphate buffer-free cathode and cell are positively related to biological nitrification, in which we suggest additional protons produced from ammonium oxidation facilitated electrochemical reduction of oxygen at cathode.     

Promises of Main Group Metal–Based Nanostructured Materials for Electrochemical CO2 Reduction to Formate

Selective CO₂ reduction to formic acid or formate is the most technologically and economically viable approach to realize electrochemical CO₂ valorization. Main group metal–based (Sn, Bi, In, Pb, and Sb) nanostructured materials hold great promise, but are still confronted with several challenges. Here, the current status, challenges, and future opportunities of main group metal–based nanostructured materials for electrochemical CO₂ reduction to formate are reviewed. Firstly, the fundamentals of electrochemical CO₂ reduction are presented, including the technoeconomic viability of different products, possible reaction pathways, standard experimental procedure, and performance figures of merit. This is then followed by detailed discussions about different types of main group metal–based electrocatalyst materials, with an emphasis on underlying material design principles for promoting the reaction activity, selectivity, and stability. Subsequently, recent efforts on flow cells and membrane electrode assembly cells are reviewed so as to promote the current density as well as mechanistic studies using in situ characterization techniques. To conclude a short perspective is offered about the future opportunities and directions of this exciting field.     

High Permittivity CaCu3Ti4O12 Particle‐Induced Internal Polarization Amplification for High Performance Triboelectric Nanogenerators

Here, a composite material based on the butylated melamine formaldehyde (BMF) and high permittivity CaCu₃Ti₄O₁₂ (CCTO) particles as a triboelectric dielectric material for stable high output triboelectric nanogenerators (TENGs) is proposed. CCTO particles, which have the high permittivity of 7500, can potentially result in the formation of strong internal polarization into the dielectric material under the electric field from triboelectric charges. As a consequence, the charge induction on the bottom electrode is enhanced thereby increasing the triboelectric output performance. A rotation‐type freestanding mode TENG based on BMF–CCTO 1 wt% composite material demonstrates high performance power output of a root‐mean‐square voltage and current density with 268 V and 25.8 mA m^?2, respectively. The strategy of incorporating the high permittivity CCTO particles can be universally applied to any triboelectric polymer matrix in order to enhance the output performance of TENGs.     

Triboelectric Nanogenerator for Sustainable Wastewater Treatment via a Self‐Powered Electrochemical Process

By harvesting the flowing kinetic energy of water using a rotating triboelectric nanogenerator (R‐TENG), this study demonstrates a self‐powered wastewater treatment system that simultaneously removes rhodamine B (RhB) and copper ions through an advanced electrochemical unit. With the electricity generated by R‐TENG, the removal efficiency (RE) of RhB can reach the vicinity of 100% within just 15 min when the initial concentration of RhB is around 100 ppm at optimized conditions. The removal efficiency of copper ions can reach 97.3% after 3 h within an initial concentration of 150 ppm at an optimized condition. Importantly, a better performance and higher treating efficiency are found by using the pulsed output of R‐TENG than those using direct current (DC) supply for pollutant removal when consuming equal amount of energy. The recovered copper layer on the cathode through R‐TENG is much denser, more uniform, and with smaller grain size (d = 20 nm) than those produced by DC process, which also hints at very promising applications of the R‐TENG in electroplating industry. In light of the merits such as easy portability, low cost, and effectiveness, this R‐TENG‐based self‐powered electrochemical system holds great potential in wastewater treatment and electroplating industry.     

[Cu(phen)2] acts as electrochemical indicator and anchor to immobilize probe DNA in electrochemical DNA biosensor

We demonstrate a novel protocol for sensitive in situ label-free electrochemical detection of DNA hybridization based on copper complex ([Cu(phen)₂]²⁺, where phen = 1,10-phenanthroline) and graphene (GR) modified glassy carbon electrode. Here, [Cu(phen)₂]²⁺ acted advantageously as both the electrochemical indicator and the anchor for probe DNA immobilization via intercalative interactions between the partial double helix structure of probe DNA and the vertical aromatic groups of phen. GR provided large density of docking site for probe DNA immobilization and increased the electrical conductivity ability of the electrode. The modification procedure was monitored by electrochemical impedance spectroscopy (EIS). Square-wave voltammetry (SWV) was used to explore the hybridization events. Under the optimal conditions, the designed electrochemical DNA biosensor could effectively distinguish different mismatch degrees of complementary DNA from one-base mismatch to noncomplementary, indicating that the biosensor had high selectivity. It also exhibited a reasonable linear relationship. The oxidation peak currents of [Cu(phen)₂]²⁺ were linear with the logarithm of the concentrations of complementary target DNA ranging from 1 × 10⁻¹² to 1 × 10⁻⁶ M with a detection limit of 1.99 × 10⁻¹³ M (signal/noise = 3). Moreover, the stability of the electrochemical DNA biosensor was also studied.     

Graphene oxide supported rhombic dodecahedral Cu2O nanocrystals for the detection of carcinoembryonic antigen

In this work, a simple electrochemical immunosensor was developed for the detection of carcinoembryonic antigen (CEA) based on rhombic dodecahedral Cu₂O nanocrystals–graphene oxide–gold nanoparticles (rCu₂O–GO–AuNPs). GO as the template and surfactant resulting in rCu₂O exhibit improved rhombic dodecahedral structure uniformity and excellent electrochemical performance. Moreover, GO was found to be able to effectively improve the long stability of rCu₂O on the electrode response. Under optimal conditions, the immunosensor showed a low limit of detection (0.004 ng ml⁻¹) and a large linear range (0.01–120 ng ml⁻¹). This work presents a potential alternative for the diagnostic applications of GO-supported special morphology materials in biomedicine and biosensors.     

Amperometric biosensor for hydrogen peroxide based on horseradish peroxidase onto gold nanowires and TiO2 nanoparticles

An electrochemical biosensor for determination of hydrogen peroxide (H₂O₂) was fabricated, based on the electrostatic immobilization of horseradish peroxidase (HRP) with one-dimensional gold nanowires (Au NWs) and TiO₂ nanoparticles (nano-TiO₂) on a gold electrode. The nano-TiO₂ can give a biocompatible microenvironment and compact film, and the Au NWs can provide fast electron transferring rate and greatly add the amount of HRP molecules immobilized on the electrode surface. Au NWs were characterized by ultraviolet–visible spectra and transmission electron microscope. The electrode modification process was probed by cyclic voltammetry and electrochemical impedance spectroscopy. Chronoamperometry was used to study the electrochemical performance of the resulting biosensor. Under optimal conditions, the linear range for the determination of H₂O₂ was from 2.3 × 10⁻⁶ to 2.4 × 10⁻³ M with a detection limit of 7.0 × 10⁻⁷ M (S/N = 3). Moreover, the proposed biosensor showed superior stability and high sensitivity.     

Hemodynamic monitoring by intracardiac impedance measured by cardiac resynchronization defibrillators: Evaluation in a controlled clinical setting (BIO.Detect HF II study)

BackgroundIn patients with cardiac resynchronization therapy defibrillators (CRT-Ds), intracardiac impedance measured by dedicated CRT-D software may be used to monitor hemodynamic changes. We investigated the relationship of hemodynamic parameters assessed by intracardiac impedance and by echocardiography in a controlled clinical setting.MethodsThe study enrolled 68 patients (mean age, 66 ± 9 years; 74% males) at 12 investigational sites. The patients had an indication for CRT-D implantation, New York Heart Association class II/III symptoms, left ventricular ejection fraction 15%–35%, and a QRS duration ≥150 ms. Two months after a CRT-D implantation, hemodynamic changes were provoked by overdrive pacing. Intracardiac impedance was recorded at rest and at four pacing rates ranging from 10 to 40 beats/min above the resting rate. In parallel, echocardiography measurements were performed. We hypothesized that a mean intra-individual correlation coefficient (r_mean) between stroke impedance (difference between end-systolic and end-diastolic intracardiac impedance) measured by CRT-D and the aortic velocity time integral (i.e., stroke volume) determined by echocardiography would be significantly larger than 0.65.ResultsThe hypothesis was evaluated in 40 patients with complete data sets. The r_mean was 0.797, with a lower confidence interval bound of 0.709. The study hypothesis was met (p = 0.007). A stepwise reduction of stroke impedance and stroke volume was observed with increasing heart rate.ConclusionsIntracardiac impedance measured by implanted CRT-Ds correlated well with the aortic velocity time integral (stroke volume) determined by echocardiography. The impedance measurements bear potential and are readily available technically, not requiring implantation of additional material beyond standard CRT-D system.