Oil spills remain a worldwide challenge and need emergency "spill-SOS" actions when they occur. Conventional methods suffer from complex processes and high cost. Here, we demonstrate a solar-heating siphon-capillary oil skimmer (S-SOS) that harvests solar energy, gravitational potential energy, and solid surface energy to enable efficient oil spill recovery in a self-pumping manner. The S-SOS is assembled by an inverted U-shape porous architecture combining solar-heating, siphon, and capillary effects, and works without any external power or manual interventions. Importantly, solid surface energy is used by capillary adsorption to enable the self-starting behavior, gravitational potential energy is utilized by siphon transport to drive the oil flow, and solar energy is harvested by solar-thermal conversion to facilitate the transport speed. In the proof-of-concept work, an all-carbon hierarchical architecture (VG/GF) is fabricated by growing vertically oriented graphene nanosheets (VGs) on a monolith of graphite felt (GF) via a plasma-enhanced method to serve as the U-shape architecture. Consequently, an oil-recovery rate of 35.2 L m-2 h-1 is obtained at ambient condition. When exposed to normal solar irradiation, the oil-recovery rate dramatically increases to 123.3 L m-2 h-1. Meanwhile, the solar-thermal energy efficiency is calculated to be 75.3%. Moreover, the S-SOS system presents excellent stability without obvious performance-degradation over 60 h. The outstanding performance is ascribed to the enhanced siphon action, capillary action, photonic absorption, and interfacial heating in the plasma-made graphene nanostructures. Multiple merits make the current S-SOS design and the VG/GF nanostructures promising for efficient oil recovery and transport of energy stored in chemical bonds.
Keywords: fluid transport; oil recovery; plasma-made nanostructures; siphon and capillary actions; solar-thermal conversion.