Sliding mode direct current triboelectric nanogenerators

Highlights: • Developed a new universally applicable working mode that enables TENG to achieve DC output. • No rectifier circuit and electrostatic breakdown improve the applicability of DC-TENG. • Three triboelectric materials realize the unidirectional flow of electric charge. • The output of DC-TENG is adjustable. The triboelectric nanogenerator (TENG), which converts mechanical energy in the environment into electrical energy, has become a promising energy harvesting technology. However, the traditional TENG is based on the coupling of contact electrification and electrostatic induction to directly generate alternating current (AC), which requires a rectifier to obtain direct current (DC) to drive electronic devices. This greatly limits the portability and energy efficiency of the energy system. In this work, a new type of DC-TENG is designed. Two conductors with different electron-obtaining abilities are selected as TENG electrodes, and the electron-obtaining ability of the triboelectric layer is between the two electrode materials. So, the triboelectric layer can continuously transfer electrons from one electrode to another, realizing a unidirectional flow of electrons. In the experiment, Cu wood and Al were selected to be assembled into a DC-TENG, without a rectifier or air breakdown, and successfully achieved a DC output. The correlation between the motion parameters and the output makes the output continuously adjustable. The rotation mode obtains a constant DC output of 80 V, 270 μA/m², and successfully charges capacitors quickly and illuminates small electronic devices. The electrodes and triboelectric layers of other materials also achieve DC output, which proves the universality of this model.