Microscale Contact Electrification with Unprecedented High Intrinsic Charge Density

Contact electrification (CE) refers to the charge generation of two materials after contact and separation, benefiting applications including electrophotography, electrostatic self-assembly, and energy harvesting. However, surface asperities lead to a low effective charging area and restrict the net CE charge density. Here, atomically flat polytetrafluoroethylene (PTFE) and graphite microflake are used to increase the contact efficiency and achieve an unprecedented intrinsic CE charge density of 2.6 mC m^-2. Crucially, the unipolar negative charging region is observed at the graphite/PTFE interface, which effectively eliminates charge cancellation and amplifies net charge density, diverging from the charge mosaic pattern. These findings provide a fundamental understanding for further material/interface development toward controllable triboelectric charge density.