Triboelectric nanogenerators (TENGs) are growing as sustainable nanogenerator and renewable technologies for capturing wasted mechanical energy from natural sources such as motion, waves, wind, and vibrations. TENG devices generate electricity using the cyclic principle of contact and separation of tribo-material couples.

This technology has exceptional applications in energy generation, human care, medicinal, biomedical, and industrial fields. TENG Sustainable Nanogenerator devices have several practical uses, including portable power, self-powered sensors, electronics, and electric consumption devices. TENG energy solutions have the potential to minimize or solve key energy concerns shortly, such as lowering petrol emissions, boosting environmental protection, and enhancing human health. TENGs’ performance can be improved using materials with considerable contrast in their triboelectrical characteristics or by implementing advanced structural designs.

Green energy collection has been intensively investigated to attain carbon neutrality in recent decades. The triboelectric nanogenerator, or TENG, is a potential green energy sustainable nanogenerator that produces various products from low-frequency mechanical energy lost during normal motion. Since its inception in 2012, TENG has been regarded as extremely useful. A triboelectric nanogenerator (TENG) is a promising sustainable nanogenerator that turns lost mechanical energy into electricity. However, cutting-edge TENGs often contain fluoropolymers, which have a high risk of releasing toxic per and poly-fluoroalkyl substances (PFAS) into the environment. Because of their stable chemical composition, PFAS can persist in the human body for long periods and pose significant health hazards, including cancer, immune system damage, and miscarriage.

Efficient and Sustainable Sulfur-Rich Composite Using MXene

In terms of cutting-edge tribo-materials for TENGs, more than half of current research has used fluoropolymers like polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), and polyvinylidene fluoride (PVDF). Fluorine has the greatest electron affinity (1328.2 kJ mol-1) and electron negativity (4.0). This implies they can effectively extract electrons from other materials while producing a high negative surface charge density. As a result, fluoropolymers are commonly used as negatively charged contact layers in the production of TENG. Despite being helpful to the material, national organizations and current research have given various warnings against employing fluoropolymers due to their polluting nature.

Source: Schematic diagram showing different application areas of TENG devices.

Sulfur-rich polymers must be produced to prevent negative repercussions on the environment and human health. They are mostly made up of 7 million tonnes of elemental sulphur obtained from the hydrodesulfurization process of petroleum refining.

During the process, elemental sulphur is recovered from hydrogen sulphide (H₂S) gas, resulting in significantly purer waste. With a maximum electron affinity of -200 kJ mol^-1 and an electron affinity of -122 kJ mol^-1, SRP is a potential element for the development of high-performance TENGs. Furthermore, because of their dynamically exchangeable disulphide bonds, end-used SRP can be reused by thermal reprocessing without significantly deteriorating mechanical qualities.

The New Nanomaterial: MXene

MXene belongs to a new family of 2D nanomaterials. It has a 2D sheet-like form with a large aspect ratio. It has metallic electrical conductivity (5000-20,000 S cm⁻¹). MXene also has a metallic core and surface terminal groups composed of oxides and fluorines, resulting in negatively charged surfaces. MXene nanosheets can be dispersed in aqueous solutions with stability, thanks to negatively charged surfaces. This also helps in environmental applications and coating processes for items with changing 3D topography. MXene requires no additional reduction or oxidation steps to obtain stable dispersion in aqueous mediums or electrical conductivity.

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Improving TENG Output Performance Using MXene

Due to its electrical conductivity and negative surface charge, microscopic dipoles are formed at the interface with the polymer matrix and MXene. This increases the dielectric constant of the polymer nanocomposites, which, in turn, improves their performance. Various studies have shown that increasing the dielectric constant of polymer nanocomposites improves their performance.

Furthermore, altering the amount of MXene enhanced TENG’s sustainable nanogenerator performance, which influenced the connectivity of the MXene structure. In this method, electrical percolation was not affected. Furthermore, only 0.4 wt% MXene was needed to produce the best output performance in TENG. Moreover, researchers used the scaling-up method and corona discharge. This led to a rise in the peak power density of the SRP/MXene TENG. This allows them to power commercial electronics such as capacitors and LEDs correctly.

Generating Ti3C2Tx MXene Nanosheets

Electrostatic repulsion between negatively charged MXene nanosheets makes it simple to disseminate them stably in aqueous mediums. The SRP Matrix is prepared by inverse vulcanization of 75 wt% elemental sulphur (S) and 25 wt% 1,3-di isopropenyl benzene (DIB) as a comonomer. This facilitates the formation of solidified SRP pieces. Furthermore, to prevent elemental sulphur recrystallization, the researchers baked SRP pieces for 10 minutes at 160°C. This aids in eliciting subsequent reactions from the unreacted species.

Chemically stable SRP pieces were pulverized into powder at a glass transition temperature (Tg) of about 17°C. The process was completed using a commercial blender and liquid nitrogen. SEM pictures show that SRP powder has an average projected area radius of 18.9 ± 14.4 µm.

Furthermore, SRP powder was thoroughly immersed in MXene aqueous solution while vigorously shaking. It was then utilized to efficiently cover MXene nanosheets by self-assembly via aqueous medium evaporation under vacuum conditions at room temperature 25°C for 72 hours.

To create an AI-electrode integrated SRP/MXene composite film, researchers applied MXene-coated SRP powder to AI foil and hot pressed it at 140° C for 2 minutes. Because the disulphide bonds in the SRP matrix can exchange dynamically at 140° C, they form a stable film when they come into physical touch at their boundaries.

Thus, a neighbouring SRP matrix with newly created disulphide linkages closely surrounds MXene layers, leaving no vacancies. This promotes consistency and stability. A comprehensive investigation was conducted into the effect of temperature on film thickness to achieve the composite film’s target thickness.

Conclusion

In conclusion, this method produced an efficient and sustainable sulfur-rich composite with MXene. It demonstrated excellent power density and closed-loop recycling while maintaining the TENG device’s performance. TENG is considered environmentally sound because it uses a wasteful element, sulphur. These films also include dynamically exchangeable disulphide bonds, allowing them to be reused through pulverization and thermal processing. This novel approach is expected to address the limitations of the existing system.

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