Surface charge density (σSC) is essential to the output of the triboelectric nanogenerator (TENG). Massive efforts have been made to improve it, which can be totally categorized into four types. Two of them are utilized to optimize the basic electrification of the TENG, and the other two are for the device configuration and following circuits. However, the basic electrification of the 100 μm-thick film under ambient conditions still stays below 200 μC m-2. Herein, we proposed a brand-new technical route, by designing an asymmetric-internal-capacitance configuration, which forms a "hot surface" rich in free electrons at the electrification interface and finally promotes σSC to 550 μC m-2. Specifically, σSC of Cu is improved by 35 times, reaching 9.48 times that of nylon that is reported to be a strong positive triboelectric material. Furthermore, the hot surface improves the output of the TENG by 12.8 times and drives multiple devices floating in water to work stably, showing great potential in harvesting water wave energy (blue energy).
Keywords: asymmetric internal capacitance; charge aggregation; hot surface; surface charge density; triboelectric nanogenerator.