Advancing Polyphenol-Based Triboelectric Nanogenerators via pH-Modulated Rapid Synthesis of Tannic Acid–Metal Complexes

Triboelectric nanogenerators (TENGs) are ideal for meeting the global demand for sustainable energy in energy harvesting and wearable electronics. While biomaterials like polysaccharides are well studied in TENGs, the potential of polyphenols and the role of phenolic groups in contact electrification remain underexplored. This study bridges the gap by using tannic acid (TA) to rapidly prepare TA-Fe³⁺ complex-coated particle films in 1.2 min. Analysis reveals that phenolic hydroxyl groups are strong electron donors, with Fe³⁺ enhancing electron affinity by restricting their mobility and lowering molecular orbital energy levels. Adjusting the pH to control complex states enables the regulation of triboelectric charging behavior between positive and negative. Investigations into film micromorphology and particle size further optimize performance, with the tris-complex exhibiting negative charging behavior achieving exceptional stability and a high charge density of 92.5 μC·m⁻². Additionally, integrating biomaterials into bio-TENGs and exploring the film’s pH and ion sensitivity broaden its applications, demonstrating versatile properties. This study clarifies the triboelectric properties of phenolic groups and proposes methods to regulate charging behavior, offering novel insights for developing biomaterials in TENGs.