A cobalt oxide@polydopamine-reduced graphene oxide-based 3D photothermal evaporator for highly efficient solar steam generation

Improving the evaporation rate and energy efficiency of solar steam generation is very important to facilitate real-world applications for clean water production. In this work, Co3O4@polydopamine (PDA) nanoparticles were synthesized and combined with reduced graphene oxide (rGO) to fabricate a new Co3O4@PDA-rGO photothermal aerogel. The obtained photothermal aerogel sheet was thereafter used to prepare both two-dimensional (2D) and three-dimensional (3D) photothermal evaporators for solar steam generation. Due to the excellent light absorption and hydrophilicity of the photothermal aerogel, a high evaporation rate of 1.60 kg·m−2·h−1 was achieved for the 2D photothermal evaporator. While for the 3D evaporator, the evaporation rate was dramatically increased to 3.71 kg·m−2·h−1 with a corresponding light-to-vapor energy efficiency of 107%. This was attributed to an increased evaporation surface area, decreased energy loss from the top evaporation surface to the environment, and energy gain from the environment on the side evaporation surface. The 3D evaporator also showed excellent practical performance in seawater desalination thus demonstrating great potential for real-world applications.