Waterproof and robust Al:GO for greatly-enhanced energy harvesting and reliable self-powered fluid velocity sensing

New applications of nanogenerators (NGs) in various environments (dry or wet) have gained increasing attention, but the mechanical strength and water resistance of active materials in nanogenerators need to be enhanced for reliable and durable performance. In this study, we propose a strategy to enhance water resistance and mechanical strength of graphene oxide (GO) membranes/films by surface treatment and cross-linking to fabricate reliable self-powered fluid sensors, and gigantically-enhanced triboelectric NGs. The bonding of Al ions dramatically improves the water resistance of GO membranes, making them suitable for immersion-type solidliquid TENGs. The water flow-induced direct-current output has an excellent linear relationship with the water flow speed (R-2 >0.99), rendering them ideal for self-powered water speed sensors. Besides, the output voltage and current of the Al:GO solid-solid TENG are increased by 18.5 and 6.7 times, respectively, by Al-containing molecular dipoles, and the durability is also greatly enhanced due to Al-induced crosslinking. This work promotes practical applications of nanogenerators for various self-powered sensing and energy harvesting in various environments.