• Energy Research

AbstractA general theoretical analysis of a 3D generic TENG structure is presented. Using a dimensionless formulation, it is demonstrated that the optimal TENG geometry does not depend on the frequency of the moving dielectric but the external ohmic impedance for maximum power output is inversely proportional to the frequency. It is also found that the energy is proportional to the cube of the size of the TENG, the square of the triboelectric charge density σT, and the angular frequency ω of the moving dielectric. In the case of a spherical TENG where the moving dielectric is a sphere and the electrodes are spherical caps on a larger sphere three dimensionless parameters that determine the harvested energy are identified: the ratio between the radii of the two spheres = r/R, the polar angle θ of the two spherical caps formed by the electrodes, and = ZεRω, whereZis the external impedance,Ris the radius of the large sphere, ε is the permittivity of the system, and ω is the angular frequency of the moving sphere. Under the crude assumption of constant charge density on the electrodes, the optimal parameters can be easily calculated. It is found that θ = 1.1 rad, = 0.67, and = 0.18.

We report the first flexible hybrid energy cell that is capable of simultaneously or individually harvesting thermal, mechanical, and solar energies to power some electronic devices. For having both the pyroelectric and piezoelectric properties, a polarized poly(vinylidene fluoride) (PVDF) film-based nanogenerator (NG) was used to harvest thermal and mechanical energies. Using aligned ZnO nanowire arrays grown on the flexible polyester (PET) substrate, a ZnO-poly(3-hexylthiophene) (P3HT) heterojunction solar cell was designed for harvesting solar energy. By integrating the NGs and the solar cells, a hybrid energy cell was fabricated to simultaneously harvest three different types of energies. With the use of a Li-ion battery as the energy storage, the harvested energy can drive four red light-emitting diodes (LEDs).

The goal of nanotechnology is to build nanodevices that are intelligent, multifunctional, exceptionally small, extremely sensitive and have low power consumption. When the nanodevice is required for applications such as in vivo biomedical sensors, a nanoscale power source is required. Although a battery or energy storage unit is a choice for powering nanodevices, harvesting energy from the environment is an essential solution for building a “self-powered” nanodevice/nanosystem, [ 1 , 2 ] which is an integration of nanodevice(s) and nano-enabled energy scavenging technologies. [ 3 ] Previously, nanogenerators (NGs) have been demonstrated that can convert mechanical energy of low (order of Hz) and high (around 50 kHz) frequencies into electricity by means of piezoelectric zinc oxide nanowires (NWs). [ 4–6 ] A single silicon NW-based heterostructure has been used to fabricate solar cells that are effective for driving an NW-based pH sensor or logic gate. [ 2 ] Still, the most abundant energy available in biosystems is chemical and biochemical energy, such as glucose. In this paper, we report an NW-based biofuel cell (NBFC) based on a single proton conductive polymer NW for converting chemical energy from biofl uids, such as glucose/blood, into electricity, using glucose oxidase (GOx) and laccase as catalyst. The glucose is supplied from the biofl uid and the NW serves as the proton conductor. Although the electrolyte solution is a choice for transferring proton, it is essential to develop a proton conductive NW in some cases, such as the case in Figure S3c (see Section III of the Supporting Information (SI)), in which the anode and cathode solution are separated. A net current is generated

Summary Vibration energy harvesting and sensing is a traditional and growing research field in which various working mechanisms and designs have been developed for an improved performance. Relying on a coupling effect of contact electrification and electrostatic induction, in the past 5 years, triboelectric nanogenerator (TENG) has been applied as a fundamentally new technology to revive the field of vibration energy harvesting and self-powered sensing, especially for low-frequency vibrations such as human motion, automobile, machine, and bridge vibrations. The demonstrated instantaneous energy conversion efficiency of ∼70% and a total efficiency up to 85% distinguished TENG from traditional techniques. In this article, both TENG-enabled vibration energy harvesting and self-powered active sensing are comprehensively reviewed. Moving toward future development, problems pressing for solutions and onward research directions are also posed to deliver a coherent picture.

All-solid-state flexible supercapacitors based on a carbon/MnO(2) (C/M) core-shell fiber structure were fabricated with high electrochemical performance such as high rate capability with a scan rate up to 20 V s(-1), high volume capacitance of 2.5 F cm(-3), and an energy density of 2.2 × 10(-4) Wh cm(-3). By integrating with a triboelectric generator, supercapacitors could be charged and power commercial electronic devices, such as a liquid crystal display or a light-emitting-diode, demonstrating feasibility as an efficient storage component and self-powered micro/nanosystems.

AbstractThe fundamental principle of piezotronics and piezo‐phototronics were introduced by Wang in 2007 and 2010, respectively. Due to the polarization of ions in a crystal that has non‐central symmetry in materials such as the wurtzite structured ZnO, GaN and InN, a piezoelectric potential (piezopotential) is created in the crystal by applying a stress. Owing to the simultaneous possession of piezoelectricity and semiconductor properties, the piezopotential created in the crystal has a strong effect on the carrier transport at the interface/junction. Piezotronics is about the devices fabricated using the piezopotential as a “gate” voltage to tune/control charge carrier transport at a contact or junction. The piezo‐phototronic effect is to use the piezopotential to control the carrier generation, transport, separation and/or recombination for improving the performance of optoelectronic devices, such as photon detector, solar cell and LED. This manuscript reviews the updated progress in the two new fields. A perspective is given about their potential applications in sensors, human‐silicon technology interfacing, MEMS, nanorobotics and energy sciences.

Vertically grown cadmium sulfide (CdS) nanowire (NW) arrays were prepared using two different processes: hydrothermal and physical vapor deposition (PVD). The NWs obtained from the hydrothermal process were composed of alternating hexagonal wurtzite (WZ) and cubic zinc blende (ZB) phases with growth direction along WZ ⟨0001⟩ and ZB [111]. The NWs produced by PVD process are single crystalline WZ phase with growth direction along ⟨0001⟩. These vertically grown CdS NW arrays have been used to converting mechanical energy into electricity following a developed procedure [Z. L. Wang and J. Song Science 312, 242 (2006)]. The basic principle of the CdS NW nanogenerator relies on the coupled piezoelectric and semiconducting properties of CdS, and the data fully support the mechanism previously proposed for ZnO NW nanogenerators and nanopiezotronics.

A theoretical model for contact-mode TENGs was constructed in this paper. Based on the theoretical model, its real-time output characteristics and the relationship between the optimum resistance and TENG parameters were derived. The theory presented here is the first in-depth interpretation of the contact-mode TENG, which can serve as important guidance for rational design of the TENG structure in specific applications.

Making salinity gradient energy practical is a great challenge. Despite recent advancements, the practicality of osmotic energy for portable electronics remains doubtful due to its limited power output and portability constraints. Here we report a method for optimizing the transport of alkali metal ions within two-dimensional nanofluidic channels and coupling it with tailored interfacial redox reactions to store the osmotic energy in a space of tens of micrometres within the cut edge of a polymer film. An ultrahigh output power density of 15,900 W m−2 has been achieved. By connecting the devices in series, commercial electronics can be powered due to the high volumetric specific energy density (9.46 Wh cm−3) and power density (106.33 W cm−3). This work introduces an approach for storing iontronic energy based on osmotic effects, providing a platform for developing renewable, ultrathin and safe power sources. © 2024, The Author(s), under exclusive licence to Springer Nature Limited.