Superhydrophilic carbon@halloysite nanotube decorated sponge composites for high efficiency solar steam generation and cleanup of crude oil

Three dimensional composite evaporators have now widely been used for solar driven steam generation. However, some issues such as weak interfacial interaction, moderate water transport ability and salt precipitation should be addressed for high efficiency solar driven interface evaporation. Here, carbon modified halloysite nanotubes (CHTs) are firmly anchored onto the skeleton of Polyvinyl alcohol (PVA) sponges for preparation of compressible and superhydrophilic CHTs/PVA evaporators (CPEs). CHTs endow the evaporator with outstanding light absorption and photothermal conversion performance. In addition, the hierarchically porous and hollow structures inside CPEs ensure the evaporator powerful water transport capability and hence excellent salt rejection behavior. Benefiting from the strong interfacial interaction between CHTs and the PVA sponge, CPEs possess superior surface stability and durability. The synergy of the solar driven interface evaporation and natural evaporation from the side walls contributes to a high evaporation rate (up to 3.49 kg m−2 h−1). The evaporation rate is maintained when CPE is mechanically compressed. Also, the sponge composite can be used for cleanup of crude oil, based on the photothermally induced decrease of oil viscosity. This study can provide inspiration to develop solar evaporators for high performance desalination and water purification.