Conventional and pulsed hybrid triboelectric nanogenerator with tunable output time and wider impedance matching range.

Sliding grating-structured triboelectric nanogenerators (SG-TENGs) can multiply transferred charge, reduce open-circuit voltage, and increase short-circuit current, which have wide application prospects in self-powered systems. However, conventional SG-TENGs have an ultrahigh internal equivalent impedance, which reduces the output voltage and energy under low load resistances (<10 MΩ). The Pulsed SG-TENGs can reduce the equivalent impedance to near zero by introducing a synchronously triggered mechanical switch (STMS), but its limited output time causes the incomplete charge transfer under high load resistances (>1 GΩ). In this paper, a conventional and pulsed hybrid SG-TENG (CPH-SG-TENG) is developed through rational designing STMS with tunable width and output time. The matching relationship among grid electrode width, contactor width of STMS, sliding speed, and load resistance has been studied, which provides a feasible solution for simultaneous realization of high output energy under small load resistances and high output voltage under high load resistances. The impedance matching range is extended from zero to at least 10 GΩ. The output performance of CPH-SG-TENG under low and high load resistances are demonstrated by passive power management circuit and arc discharge, respectively. The general strategy using tunable STMS combines the advantages of conventional and pulsed TENGs, which has broad application prospects in the fields of TENGs and self-powered systems.

Power management strategy for unidirectional current pulsed triboelectric nanogenerator.

Power management circuit (PMC) can efficiently store the output energy of pulsed triboelectric nanogenerator (Pulsed-TENG). Unidirectional current Pulsed-TENG (UP-TENG) has the advantage of without using rectifier bridge. However, the energy storage efficiency is limited for large capacitors at low capacitor voltage (<10 V). To solve this problem, PMC is optimized here. Firstly, rectifier diode is used to reduce the energy loss. Energy storage efficiency of PMC using rectifier diode (D-PMC) is higher than that of conventional PMC. Then, appropriate inductor is used to further form the optimized PMC (O-PMC), which reduces the energy loss of inductor. Results show that O-PMC using 100µH inductor has the highest energy storage efficiency. The actual test energy storage efficiency of O-PMC is 30.6%, which 3.4 times higher than that of D-PMC. Finally, an external capacitor is connected to electrodes of UP-TENG to form the EUP-TENG, which improves charging speed and output voltage of O-PMC. O-PMC using EUP-TENG can stably power calculator at low motion frequencies. O-PMC can be widely used in self-powered systems.

The water droplet with huge charge density excited by triboelectric nanogenerator for water sterilization.

Water is one of the most essential resources for the survival of human beings and all other living things. For the point of daily use, water sterilization has enormous social and economic significance, especially for remote and undeveloped areas. Here, we developed a self-powered water sterilization device, which consists of a rotating-disk freestanding triboelectric-layer mode triboelectric nanogenerator (RF-TENG), a voltage-multiplying circuit, and a water droplet control system. The output voltage of the RF-TENG is boosted by a voltage-multiplying circuit and then utilized to charge water droplet. When the rotation rate of the RF-TENG is 300 rpm, the output voltage of a six-fold voltage-multiplying circuit can reach 9319 V, and a 62.50µl water droplet can be positively charged to 6320 nC at the flow rate of 0.31 ml min-1. The charge density and electric filed of the water droplet can reach 101.12 nCµl-1and 11.28 kV cm-1, respectively. The charged water droplet can killE. coliandS. aureusquickly and efficiently through electroporation mechanism. With the advantages of low cost, simple in fabrication and usage, portability, and etc, the self-powered water sterilization device has wide application prospects in remote and undeveloped areas.

A robust all-inorganic hybrid energy harvester for synergistic energy collection from sunlight and raindrops.

As a new concept of the device, a hybrid energy harvester integrated with a water droplet triboelectric nanogenerator (WD-TENG) and a solar cell has been reported to convert raindrop energy and solar energy into electricity. However, organic triboelectric layers are usually utilized in previous studies that might be decomposed under long-term UV irradiation, resulting in degradation of the hybrid energy harvester. In this work, a fully inorganic hybrid energy harvester is demonstrated. Superhydrophobic SiO2 film is introduced to the system as both the triboelectric layer of the WD-TENG and the anti-reflective layer of the solar cell, which could increase the power conversion efficiency (PCE) of the solar cell from 15.17% to 15.71%. Meanwhile, WD-TENG with the SiO2 triboelectric layer could collect energies from rain droplets. This superhydrophobic SiO2 film could effectively reduce the dependence of the tilt angle for the WD-TENG and bring up self-cleaning performance for the hybrid energy harvester. Moreover, this fully inorganic architecture could enhance the stability of the hybrid energy harvester, making it a promising strategy in practical applications.

Recent Advances in Triboelectric Nanogenerators: From Technological Progress to Commercial Applications.

Serious climate changes and energy-related environmental problems are currently critical issues in the world. In order to reduce carbon emissions and save our environment, renewable energy harvesting technologies will serve as a key solution in the near future. Among them, triboelectric nanogenerators (TENGs), which is one of the most promising mechanical energy harvesters by means of contact electrification phenomenon, are explosively developing due to abundant wasting mechanical energy sources and a number of superior advantages in a wide availability and selection of materials, relatively simple device configurations, and low-cost processing. Significant experimental and theoretical efforts have been achieved toward understanding fundamental behaviors and a wide range of demonstrations since its report in 2012. As a result, considerable technological advancement has been exhibited and it advances the timeline of achievement in the proposed roadmap. Now, the technology has reached the stage of prototype development with verification of performance beyond the lab scale environment toward its commercialization. In this review, distinguished authors in the world worked together to summarize the state of the art in theory, materials, devices, systems, circuits, and applications in TENG fields. The great research achievements of researchers in this field around the world over the past decade are expected to play a major role in coming to fruition of unexpectedly accelerated technological advances over the next decade.

Challenges and advances of organic electrode materials for sustainable secondary batteries.

Organic electrode materials (OEMs) emerge as one of the most promising candidates for the next-generation rechargeable batteries, mainly owing to their advantages of bountiful resources, high theoretical capacity, structural designability, and sustainability. However, OEMs usually suffer from poor electronic conductivity and unsatisfied stability in common organic electrolytes, ultimately leading to their deteriorating output capacity and inferior rate capability. Making clear of the issues from microscale to macroscale level is of great importance for the exploration of novel OEMs. Herein, the challenges and advanced strategies to boost the electrochemical performance of redox-active OEMs for sustainable secondary batteries are systematically summarized. Particularly, the characterization technologies and computational methods to elucidate the complex redox reaction mechanisms and confirm the organic radical intermediates of OEMs have been introduced. Moreover, the structural design of OEMs-based full cells and the outlook for OEMs are further presented. This review will shed light on the in-depth understanding and development of OEMs for sustainable secondary batteries.

Triboelectric Plasma CO2 Reduction Reaching a Mechanical Energy Conversion Efficiency of 2.3.

Mechanical energy-induced CO2 reduction is a promising strategy for reducing greenhouse gas emissions and simultaneously harvesting mechanical energy. Unfortunately, the low energy conversion efficiency is still an open challenge. Here, multiple-pulse, flow-type triboelectric plasma with dual functions of harvesting mechanical energy and driving chemical reactions is introduced to efficiently reduce CO2 . CO selectivity of 92.4% is achieved under normal temperature and pressure, and the CO and O2 evolution rates reach 12.4 and 6.7 µmol h-1 , respectively. The maximum energy conversion efficiencies of 2.3% from mechanical to chemical energy and 31.9% from electrical to chemical energy are reached. The low average electron energy in triboelectric plasma and vibrational excitation dissociation of CO2 with low barrier is revealed by optical emission spectra and plasma simulations, which enable the high energy conversion efficiency. The approach of triboelectric plasma reduction reported here provides a promising strategy for efficient utilization of renewable and dispersed mechanical energy.

The Regulation of O2 Spin State and Direct Oxidation of CO at Room Temperature Using Triboelectric Plasma by Harvesting Mechanical Energy.

Oxidation reactions play a critical role in processes involving energy utilization, chemical conversion, and pollutant elimination. However, due to its spin-forbidden nature, the reaction of molecular dioxygen (O2) with a substrate is difficult under mild conditions. Herein, we describe a system that activates O2 via the direct modulation of its spin state by mechanical energy-induced triboelectric corona plasma, enabling the CO oxidation reaction under normal temperature and pressure. Under optimized reaction conditions, the activity was 7.2 µmol h-1, and the energy consumption per mole CO was 4.2 MJ. The results of kinetic isotope effect, colorimetry, and density functional theory calculation studies demonstrated that electrons generated in the triboelectric plasma were directly injected into the antibonding orbital of O2 to form highly reactive negative ions O2-, which effectively promoted the rate-limiting step of O2 dissociation. The barrier of the reaction of O2- ions and CO molecular was 3.4 eV lower than that of O2 and CO molecular. This work provides an effective strategy for using renewable and green mechanical energy to realize spin-forbidden reactions of small molecules.

Self-Powered Intelligent Water Meter for Electrostatic Scale Preventing, Rust Protection, and Flow Sensor in a Solar Heater System.

Triboelectric nanogenerators (TENGs) have been investigated for mechanical energy harvesting because of their high-energy conversion efficiency, low cost, ease of manufacturing, and so on. This paper deals with designing a kind of water-fluid-driven rotating TENG (WR-TENG) inspired by the structure of a water meter. The designed WR-TENG is effectively integrated into a self-powered electrostatic scale-preventing and rust protection system. The WR-TENG can generate a constant DC voltage up to about 7.6 kV by using a voltage-doubling rectifier circuit (VDRC) to establish a high-voltage electrostatic field in the water tank. A WR-TENG, a VDRC, and an electric water heating tank are the components of the whole system. The system is convenient to be installed in any waterway system, effectively preventing the rusting of stainless steel and restraining the formation of scale when the water is heated to 65 ± 5 °C. Moreover, the approximately linear relationship between the short-circuit current and the rotation rate of the WR-TENG makes employing it as a self-powered water flow sensor possible. This work enables a facile, safe, and effective approach for electrostatic scale prevention, rust protection, and flow sensing in solar heaters, which will enrich the high-voltage applications of TENGs.