Triboelectric nanogenerator (TENG) is a new cost-effective blue energy harvesting technology for its great performance in low frequency. However, many related energy harvesters operate on water surface, ignoring the ocean’s depth. Herein, a chain-flipped plate TENG (CFP-TENG), consisting of longitudinally arranged repeating units, is proposed to collect wave energy. The chain structure design allows the surface wave energy to act effectively on the underwater generator. The maximum output power per unit ocean area reaches 1.5 W·m⁻² at a loading resistance of 30 MΩ. Optimization of device parameters and application demonstrations are explored. Compared with previous works, the utilization rate of wave energy has been significantly improved. This work not only provides a new method to optimize the output of TENG but also makes a crucial step in promoting practical applications of TENG in renewable blue energy.

Enhancement of supercapacitors (SCs) with high-energy density and high-power density is still a great challenge. In this paper, a facile strategy for in situ anchoring of Co₃O₄ particles on N doped carbon cloth (pCoNCC) is reported. Due to the interaction of the doped N and Co₃O₄, the electrochemical performance improves significantly, reaching 1,940.13 mF·cm^-2 at 1 mA·cm^-2 and energy density of 172.46 µWh·cm^-2 at the power density of 400 µW·cm^-2, much larger than that without N doping electrode of 28.5 mF·cm^-2. An aqueous symmetric supercapacitor (ASSC) assembled by two pCoNCC electrodes achieves a maximum energy density of 447.42 µWh·cm^-2 and a highest power density of 8,000 µW·cm^-2. Utilizing such a high-energy storage ASSC, a digital watch and a temperature-humidity detector are powered for nearly 1 and 2 h, respectively. Moreover, the ASSC displays a superb electrochemical stability of 87.7% retention after 10,000 cycles at 40 mA·cm^-2. This work would provide a new sight to enhance active materials performance and be beneficial for the future energy storage and supply systems.

Miniaturized mobile electronic devices have aroused great attention due to their convenience to daily life. However, they still face a problem that power supply from the conventional cell needs to be regularly charged or replaced. Portable electricity supply collecting energy from environment is highly desired. Herein, a highly flexible and stretchable Miura folding based triboelectric nanogenerator (MF-TENG) is prepared by using flexible polyethylene terephthalate (PET) as a folding substrate with a double working side design, specifically one side as the main TENG (M-TENG) and other side as the excitation TENG (E-TENG). The E-TENG supplements charge to M-TENG by a half-wave rectifier circuit. This design increases the TENG working area and reduces its volume. The output performance of the TENG based on Miura folding with charge excitation called MF-CE-TENG is greatly boosted. The optimal output charge and maximum peak power of MF-CE-TENG achieves 1.54 μC and 5.17 mW at 1 Hz, respectively, which is 4.61 and 10.55 times as much as that of MF-TENG without charge excitation. To demonstrate its applications, the MF-CE-TENG is used to light up 456 LEDs brightly and charge a 100 μF capacitor to 6.07 V in 5 min. A calculator and a temperature-humidity sensor work normally powered by MF-CE-TENG with an energy management module. This work provides a new strategy to enhance the output energy of Miura folding TENG by applying a charge excitation mode for the first time, which might be an effective approach to be used in other TENGs.

To obtain symmetric supercapacitors (SCs) with high energy density, it is critical to fabricate an electrode with wide potential window and excellent capacitive performance. Herein, by using the strong double hydrolysis reaction between anions and cations, the FeOOH nanosheets on the surface of activated carbon cloth (FeOOH@AC) are prepared through a simple hydrothermal process. The FeOOH@AC electrode exhibits maximum capacitance of 4,090 mF·cm^-2 at wider potential window -1-0 V and 3,250 mF·cm^-2 at 0-1 V versus SCE in 2 M LiNO₃ electrolyte. With two pieces of FeOOH@AC electrodes the obtained symmetric SC can operate at the voltage window of 2 V. This FeOOH symmetric SC shows high energy density of 13.261 mWh·cm^-3 at a power density of 14.824 mW·cm^-3 and maintains 4.175 mWh·cm^-3 at a maximum power density of 118.564 mW·cm^-3, as well as excellent charge storage capacity and cyclic stability. Li ion adsorption and diffusion mechanism on the (200) facets of FeOOH are explained by the density functional theory (DFT) calculations. The simple synthesis process and excellent capacitance performance of the FeOOH@AC composite make it a very promising candidate for high performance symmetric SC electrodes.

The triboelectric nanogenerator has attracted global attention since it was proposed in 2012; the exploration of new applications is ongoing with much enthusiasm in this field. In this paper, we present a novel triboelectric nanogenerator based on magnetically induced retractable spring steel tapes (MR-TENG) to develop energy harvesting from large amplitude periodic motion, which is an ingenious design that employs a new material. The tape-like structural design ensures that the contact/separate direction of the friction layers is perpendicular to the direction of the external force, breaking the amplitude limitation of previous nanogenerators with vertical contact/separate motion. Combined with flexible spring steel tapes, this design enables portability thus widening its application. The working mechanism and factors that may affect the output performance are systematically studied. The results show that the maximum short-circuit current, open-circuit voltage and instantaneous power are 21 μA, 342 V, and 1.8 mW, respectively. Moreover, we also demonstrate the great potential of the MR-TENG to serve as a self-powered displacement sensor and portable emergency power supply. This work greatly widens the applications of triboelectric nanogenerators (TENGs) through new material selection and innovative structural design.

Polydimethylsiloxane (PDMS) is an excellent material for investigating the mechanism of triboelectricity as it can easily be used to construct various microstructures. In this study, micro-capacitors (MCs) and variable micro- capacitors (VMCs) were embedded in PDMS by filling PDMS with silver nanoparticles (NPs) and constructing an internal cellular structure. The output performance of the triboelectric nanogenerators (TENGs) based on MCs@PDMS and VMCs@PDMS films was systematically investigated, with variation of the filling content of silver NPs and the pore ratio and size. The microstructure, permittivity, dielectric loss, and capacitance of the VMCs@PDMS films were well characterized. The output current of the TENG based on the VMCs@PDMS film was respectively 4.0 and 1.6 times higher than that of the TENGs based on the pure PDMS film and MCs@PDMS film, and the output power density of the former reached 6 W·m^–2. This study sheds light on the physical nature of conductive nanoparticle fillings and cellular structures in dielectric triboelectric polymers.

A flexible and transparent triboelectric nanogenerator (FT-TENG) has great potential for application in self-powered biosensor systems, electronic skin and wearable electronic devices. However, improving the output performance with little damage to its optical properties is challenging. Herein, we have developed an FT-TENG that has a well-ordered nest-like porous polydimethylsiloxane (NP-PDMS) film and graphene transparent electrodes. The NP-PDMS film with ordered pores is fabricated by hydrochloric acid etching of 500 nm sized ZnO spheres made of aggregated nanoparticles, having a light transmittance of 81.8% and a water contact angle of 118.62°. The FT-TENG based on the NP-PDMS film with a porosity of 12%, gives a maximum output of 271 V and 7.8 μA, which are respectively, 3.7 and 2.1-fold of those of a TENG with a flat PDMS film. The peak output power reaches 0.39 mW with a load resistance of 9.01 MΩ. The dielectric constant and effective thickness of the NP-PDMS film and the capacitance and charge transfer of the FT-TENG are systematically investigated. This work provides a novel and effective method to enhance the performance of FT-TENGs with little damage to their optical properties.

Integrated multilayered triboelectric nanogenerators (TENGs) are an efficient approach to solve the insufficient energy problem caused by a single-layered TENG for achieving high output power density. However, most integrated multilayered TENGs have a relatively large volume. Here, a double-induced-mode integrated triboelectric nanogenerator (DI-TENG) based on spring steel plates is presented as a cost-effective, simple, and high-performance device for ambient vibration energy harvesting. The unique stackable rhombus structure, in which spring steel plates act both as skeletons and as electrodes, can enhance the output performance and maximize space utilization. The DI-TENG with five repeated units in a volume of 12 cm × 5 cm × 0.4 cm can generate a short-circuit current of 51 μA and can transfer charges of 1.25 μC in a half period. The contrast experiment is conducted systematically and the results have proved that the DI-TENG has a great advantage over the single-induced-mode TENG (SI-TENG) with only one side of a friction layer on its electrode. Besides, the DI-TENG can easily power a commercial calculator and can be used as a door switch sensor.