Three-dimensional multimodal porous graphene-carbonized wood for highly efficient solar steam generation

Recently, solar steam generation systems have become a promising solar energy technology that can alleviate the energy crisis and reduce water pollution. However, because of weak solar radiation energy, rapid heat loss, and negative environmental impacts, there are still numerous challenges that must be overcome before solar steam generation systems can be used for practical energy utilization. Inspired by natural tree transpiration, this paper reports a 3D carbonized wood (hydrophilic)-based photothermal system coated with 2D porous reduced graphene oxide (hydrophobic) to promote solar steam generation. Wood with vertically aligned microchannels and high hydrophilicity is used to efficiently pump water, which is then spread to a 2D porous reduced graphene oxide layer with a sufficient evaporation surface. The unique 3D micro-sized water reservoirs formed between the wood and reduced graphene oxide maximize the thermal energy use of the graphene layer by preventing heat loss from its transference to the water and reducing light reflection. The evaporation rate and solar energy conversion efficiency were 1.492 kg⋅m−2⋅h−1 and 94.7% under 1 sun illumination, respectively. Moreover, our solar steam evaporator maintained its original evaporation rate after 20 h. This work provides new insights into the structural design for highly efficient solar steam generation devices.