Interfacial Polarization and Dual Charge Transfer Induced High Permittivity of Carbon Dots‐Based Composite as Humidity‐Resistant Tribomaterial for Efficient Biomechanical Energy Harvesting

Abstract

Tribopositive, scalable, and biocompatible materials are highly desired for high‐performance triboelectric nanogenerators (TENGs). In this study, polyethylenimine (PEI) functionalized N‐doped carbon dots (NCDs‐PEI) are synthesized and a novel approach to develop high‐output TENGs by incorporating high permittivity NCDs‐PEI into polyvinyl alcohol (PVA) as the tribopositive composite (CPP composite) is proposed for the first time. By systematically manipulating the mass ratio of NCDs/PVA and PEI‐functionalized concentration, the optimized CPP composite‐based TENGs (CPP‐TENGs) reveal a remarkable enhancement in power density by 28.5 times as compared with pure PVA‐based TENGs. The considerable electric outputs of CPP‐TENGs can be attributed to the synergistic effect of interfacial polarization enhanced permittivity of CPP composite and boosted surface charge density induced by dual charge transfer pathways. Moreover, CPP‐TENGs present superior high‐output stability, durability, and humidity‐resistance, and can also effectively drive electronics at different humidity and monitor human body movements. This work renders a simple, feasible, and scalable pathway to boost the electrical performance of TENGs for biomotion energy harvesting as well as providing insights for exploiting novel tribomaterials in the development of high‐output TENGs.

Achieving Ultrahigh Effective Surface Charge Density of Direct‐Current Triboelectric Nanogenerator in High Humidity

“…With the surface permeable [19][20][21] and hydrophobic treatment [22][23][24][25] to suppress the dissipation of triboelectric charges, TENG can maintain the charge density of 115 µC m −2 even if the humidity increases up to 90%. [26] Moreover, utilizing absorbent materials [27][28][29][30][31] to make water molecules participate in triboelectrification and generate more triboelectric charges, the output performance of TENG is further improved to 244 µC m −2 with the RH increasing to 90%. [32] Recently, some useful strategies, such as fast charge accumulation [33] and charge excitation strategy [34] can break through the limitation of material triboelectrification and achieve a recorded charge density of ≈1.30 and 1.40 mC m −2 at 90% RH and 85% RH.…”

“…Meanwhile, there are some effective strategies to enhance the surface charge accumulation for further improving the output performance in high humidity. Taking advantage of polyvinyl alcohol, [27] cellulose, [28] starch, [29] and other absorbent materials, [30][31][32] water molecules are fixed on the surface of triboelectric materials and participate in the triboelectrification process. Despite the TENGs based on absorbent materials generate more triboelectric charges in high humidity conditions, their surface charge densities are still relatively low due to the limitation of their intrinsic triboelectrification property.…”

Wearable Triboelectric Nanogenerators Based on Polyamide Composites Doped with 2D Graphitic Carbon Nitride

“…In addition, the charge transfer is already sensitive and significant even at lower frequencies, so the charge may not be able to increase significantly at higher frequencies. The power density, intrinsic impedance, and energy conversion efficiency of energy harvesting from electrospinning membrane TENGs with this material should be further optimized in the future by regulating materials composition, inventing unique structures, and employing power management circuits [ 22 , 23 , 24 , 25 ].…”

Ionic Thermoelectric Effect Inducing Cation‐Enriched Surface of Hydrogel to Enhance Output Performance of Triboelectric Nanogenerator

“…The output performance of TENG is heavily dependent on the surface charge density of the friction material. [23][24][25] Hence, it becomes important to control the interface charge density by changing the properties of friction materials. [16,26,27] The most robust consensus related to ionic-hydrogel-based triboelectric nanogenerator (TENG) is that the charge density at the solid interface plays a pivotal role in its output performance.…”

“…The output performance of TENG is heavily dependent on the surface charge density of the friction material. [ 23–25 ] Hence, it becomes important to control the interface charge density by changing the properties of friction materials. [ 16,26,27 ]…”