Recent Advances towards Ocean Energy Harvesting and Self‐Powered Applications Based on Triboelectric Nanogenerators

Abstract

Ocean contain abundant clean energies including tidal and wave, but such energies are known for low frequency and large excitation amplitude, posing considerable challenges for high‐efficiency energy conversion. As an emerging technology, triboelectric nanogenerators (TENGs) have been widely used in energy harvesting and novel sensor design due to their high sensitivity and flexible structure. Meanwhile, they show great advantages in the low‐frequency environment (<5 Hz), and display great potential for deployment in remote ocean waters, and construction of large‐scale TENG networks. In this review, firstly, the working principle of TENGs and various configurations developed for the marine environment are introduced, which mainly include solid–solid and solid–liquid interfaces. Then, from the viewpoint of power improvement, authors are most concerned about the modification methods of materials such as surface modification, electron injection, and chemical doping. Meanwhile, improved technologies for energy harvesters in marine environment are discussed in detail, such as improving the hydrophobicity and degradation of materials, studying the self‐healing ability of materials, and designing power management circuits. Finally, the current challenges are summarized, and research trends are given from both short‐term and long‐term perspectives.

Liquid–Polymer Contact Electrification: Modeling the Dependence of Surface Charges and ξ-Potential on pH and Added-Salt Concentration

“…The electrification of water droplets after sliding or rolling on hydrophobic surfaces has increasing interest for its applications in energy harvesting devices. − A particular case corresponds to the slide/roll of water drops on hydrophobic polymers, poly­(tetrafluoroethylene) (PTFE) being the paradigmatic polymer for observing this phenomenon. The situation to describe is the following: water drops are delivered, one after another, on the tilted (almost vertical) surface of a hydrophobic polymer (see Figure ).…”

“…We propose here that both phenomena, the LPCE generated during drop sliding/rolling and the establishment of ξ-potential at the polymer–solution interface, may have the same origin: the acid–base equilibrium on the polymer surface. The subject is still under debate, and although it is commonly observed that surfaces of several hydrophobic polymers in contact with neutral water (pH = 7) acquire a negative charge, this is not always exclusively explained or interpreted by assuming OH – adsorption but by asymmetries in the H-bond at the surface or electron transfer processes. ,, …”

An Atlas of Piezoelectric Energy Harvesters in Oceanic Applications

“…Most recently, as oceans contain a huge amount of energy and are completely predictable and reliable, the generation of electricity based on oceans is becoming very popular. Electricity generation from oceanic energies can be either on large-scales [5], such as wave activated bodies [6], point absorbers [7,8], oscillating water columns [9], and overtopping [10] concepts, for cities and industries, or on small-scales using piezoelectric [11], electrostatics [12], electromagnetics [13], and triboelectric [14] devices for powering low power devices, such as the internet of underwater things, sensors, and other monitoring devices in oceans [15].…”

Underwater Energy Harvesting to Extend Operation Time of Submersible Sensors

“…The majority of the devices shown in this review work with TENG or hybrid systems, TENG and EMH (electromagnetic harvesting). Shen et al [ 17 ] presented recent advances towards ocean energy harvesting and self-powered applications based on triboelectric nanogenerators and the study of different materials and configurations. In this review, it was stated that at present, the most employed hybrid generator is the EMG (electromagnetic generator)-TENG, as EMGs increase the current of hybrid generators.…”