Femtosecond Laser Opening Hierarchical Lamination: Micro-Nano Hybrid Scissoring of Three-Dimensional Nitrogen-Doped Graphene for Solar Steam Generation

Three-dimensional (3D) nanoporous nitrogen-doped graphene is an ideal candidate for solar steam generation. However, the outermost dense layer formed during high-temperature thermal chemical vapor deposition (CVD) severely blocks water transport and steam escape. In this work, a technique of femtosecond laser opening hierarchical lamination (FLOHL) enabling hierarchical micro-nano hybrid scissoring of graphene is presented for its structural and performance upgrades. FLOHL not only allows noncontact rapidly hierarchical opening of the blocked layer but also enables opening lamination of close thin-wall graphene into suspended sheets, while maintaining a robust connection with the framework facilitating stable repetitive use for water evaporation. After FLOHL, solar absorption, heat localization, and interfacial wetting are all dramatically enhanced, increasing water evaporation rates from 1.58/1.56 to 1.79/1.77 kg m^-2 h^-1 for two prototypes under 1 sun irradiation and conversion efficiency from ∼80% to ∼90%, making them better than many solar evaporators built with graphene and its derivatives, including laser-induced graphene.