Synchronous nanogenerator with intermittent sliding friction self-excitation for water wave energy harvesting

The triboelectric nanogenerator (TENG) is a promising technology for harvesting low-frequency ocean energy, while a low surface charge density sets back its industrialization. Normally, owing to insufficient friction the traditional contact-separation mode has difficulty achieving a high surface charge density as that of sliding friction mode, which also can hardly maintain long-term sustenance due to abrasion. Herein, we designed a synchronous contact-separation triboelectric nanogenerator (SC-TENG) with intermittent sliding friction self-excitation that can achieve the dual functions of long-term sustenance of a high surface charge density and low friction-induced loss. A movable pendulum structure rotates intermittently to replenish the charge for its own, thus sustaining a high surface charge density for continuous contact-separation working mode. Several comparative experiments are conducted, showing short-time sliding friction made it easier to improve the surface charge density and output performance than long-term contact-separation friction. The single TENG with short-term friction increases by seven-fold in the transferred charges, 3.2 times in output current, compared to the TENG without friction. The SC-TENG could generate a high voltage of 1284 V and maximum peak power of 8.3 mW at 1 Hz. With those capacities, the TENG can easily capture the water wave energy to power a commercial thermohygrometer and portable wearable device. SC-TENG proposes an innovative design and a new strategy for preparing the TENG with high output and low loss. A movement pattern that cleverly combines the advantages of the vertical contact-separation mode and sliding friction is proposed. It has the effect of self-excitation that increases the transferred charges by 7 times, and other membrane materials also have this effect. The TENG achieves the dual functions of long-term high performance and low loss and has the excellent capability of harvesting the random disordered water wave energy. • A friction self-excited mode is proposed that significantly increases the surface charge density of materials. • A synchronous TENG with this mode can achieve the dual functions of long-term high performance and low loss. • The TENG has the excellent capability of harvesting water wave energy.