Graphene nanoplatelet-chitosan coated melamine foam with Janus structure for solar steam generation

Interfacial solar steam generation is a sustainable and emerging technique to collect water from seawater desalination. Herein, motivated by the porous structure and hydrophilicity of melamine foam (MF), a hydrophobic/hydrophilic (cup-cone shaped) graphene nanoplatelets/chitosan (GnPs/CS) coated melamine foam (GCM) is developed. However, the Janus structure of GCM, with its advantage of a hydrophobic top surface and a hydrophilic bottom surface, not only reduces heat losses to bulk water but also ensures water transport, enhances light absorption (96%), and stabilizes the evaporator, mitigating salt accumulation. Due to this fabrication strategy, the evaporation rate (ER) of water and the photothermal conversion efficiency of GCM are 1.42 kgm-2 h-1 and 95.7%, respectively, under 1 sun (1 kWm-2) irradiation. The real seawater ER of 1.39 kgm-2 h-1 under 1 sun irradiation has been achieved. Furthermore, the removal of 99% of methylene blue and Rhodamine-B dyes highlights its potential for various applications in wastewater purification, desalination, and sustainable water production. These findings underscore the significance of this composite device as a pivotal advancement in sustainable solar-driven technologies and its potential to address critical global challenges related to access to clean water.