Anomalous output performance enhancement of RGO-based triboelectric nanogenerators by Cu-bonding

Since the invention of triboelectric nanogenerators (TENGs), many approaches have been proposed to enhance their performances by modifying the triboelectric materials, mostly attributed to the increase in work function differences or effective contact area. In the work, we firstly demonstrate the output performance enhancement distinctly by the effect of surface dipoles rather than the common approaches. By bonding copper ions onto the oxygen-containing functional groups of graphene oxides, the orientations of surface molecular dipoles are inverted, leading to the output enhancement of the TENG. Interestingly, the variations of the output performances of the TENGs with surface modifications are just opposite to the predictions from the differences in work functions, measured by Kelvin probe force microscopy. The work implies that other important factors dominating the performances of TENGs than work functions. A self-bias-enhancement model by surface dipoles is proposed and testified by further polling processes. The mechanisms should be universal to other materials for enhancing the performances of TENGs and self-powered devices.