Light-propelled photocatalytic evaporator for robotic solar-driven water purification

Abstract Solar-driven interfacial water purification (SDIWP) has emerged as a green, cost-effective, and sustainable technology for waste/sea water treatment. However, at present, innovative smart water treatment systems that enable high-efficiency water purification through multiform solar schemes are rare. Herein, we report a light-propelled photocatalytic evaporator based on semi-metallic reduced graphene oxide (RGO)/ titanium carbide MXene-titanium dioxide (Ti 3 C 2 T x -TiO 2 ) ternary hybrid foams for multi-scheme SDIWP. The RGO/Ti 3 C 2 T x -TiO 2 foam is prepared by freeze-drying induced self-assembly (FDISA) of Ti 3 C 2 T x and graphene oxide (GO) nanosheets by which an in-situ redox reaction between Ti 3 C 2 T x and GO nanosheets occurs and TiO 2 nanoparticles are generated simultaneously. The synergistic effect leads to the formation of the semi-metallic RGO/Ti 3 C 2 T x -TiO 2 framework with the Ti–O-C covalent bonding between RGO and Ti 3 C 2 T x . Under light irradiation, the photogenerated carriers in RGO/Ti 3 C 2 T x -TiO 2 can occupy the quantum-confined graphene-like states in RGO with an average lifetime of 0.8 ps, this value is 2 orders of magnitude shorter than that of GO and Ti 3 C 2 T x . As a result, the RGO/Ti 3 C 2 T x -TiO 2 foam shows photocatalytic degradation activity and photothermal conversion ability, enabling multi-scheme SDIWP. Owing to its excellent photothermal properties and quantum-confined superfluidic structures, the RGO/Ti 3 C 2 T x -TiO 2 foam exhibits superior vapor generation performance (1.72 kg m –2 h –1 ). Furthermore, the photocatalytic evaporator can be remotely manipulated as a floating robot for water treatment through programmable light navigation via photothermal Marangoni propulsion. This work provides a new approach for developing robotic SDIWP systems.