Engineering polymers with quantified charge affinities are commonly used materials in triboelectric nanogenerators (TENGs). A polymer can have only one specific charge affinity due to its uniform chemical composition, leading to the need for two different materials to make an effective TENG. However, unlike engineering polymers, half-cell plant skins can have different charge affinities on their outer and inner surfaces. Here, we report a study on the hetero-triboelectric effects (HTEs) of half-cell allium plant skins such as leek, scallion and onion. Single-material TENGs (SM-TENGs) have been fabricated based on the two surfaces of these plant skins, taking advantage of their HTEs. The highest output power density of up to 35 W m−2 has been achieved with an output stability of over 5400 cycles. Multiple applications of SM-TENGs have been discovered, including energy harvesting, gas sensing, and humidity sensing, which are unique from other TENGs. Additionally, these SM-TENGs have an advantage due to the natural biological and chemical structures of the skins.