The direct conversion of mechanical energy into electricity by nanomaterial-based devices offers potential for green energy harvesting1,2,3. A conventional triboelectric nanogenerator converts frictional energy into electricity by producing alternating current (a.c.) triboelectricity. However, this approach is limited by low current density and the need for rectification2. Here, we show that continuous direct-current (d.c.) with a maximum density of 106 A m−2 can be directly generated by a sliding Schottky nanocontact without the application of an external voltage. We demonstrate this by sliding a conductive-atomic force microscope tip on a thin film of molybdenum disulfide (MoS2). Finite element simulation reveals that the anomalously high current density can be attributed to the non-equilibrium carrier transport phenomenon enhanced by the strong local electrical field (105−106 V m−2) at the conductive nanoscale tip4. We hypothesize that the charge transport may be induced by electronic excitation under friction, and the nanoscale current−voltage spectra analysis indicates that the rectifying Schottky barrier at the tip–sample interface plays a critical role in efficient d.c. energy harvesting. This concept is scalable when combined with microfabricated or contact surface modified electrodes, which makes it promising for efficient d.c. triboelectricity generation.
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This work was supported by the Canada Excellence Research Chair (CERC) program at the University of Alberta, the National Research Foundation of Korea (NRF) grants funded by the Ministry of Science, ICT & Future Planning (NRF-2017R1A2B3009610 and NRF-2017R1A4A1015564), the Natural Science Foundation of China (Grant No. 51776126) and the Yunnan Provincial Science and Technology Department School Science and Technology Cooperation Project (grant no. 2014IB007). The authors would like to thank S. Xu, A. He and N. Zhang from Nanofab at the University of Alberta for material characterization, and thank K. Schofield, U. Rengarajan, D. Majak and D. Scott for discussions. The authors would also like to acknowledge support from the Alberta Innovates-Technology Futures (AITF) Graduate Scholarship.
The authors declare no competing financial interests.
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