A self-floating photothermal evaporator with 3D gradient water channel for highly efficient solar seawater desalination

Abstract

Solar-driven photothermal interface evaporation is considered one of the most promising strategies for dealing with seawater desalination for the scarcity of freshwater resources. However, it still faces the challenges of achieving superior optical absorption combined with outstanding evaporation performance. So as to improve the utilization of solar energy and reduce the loss of heat transfer. We designed a unique three-dimensional self-floating gradient composite membrane via the method of spray, speed shear, and sinking. In this research, a self-floating Polyvinylidene fluoride/Multi-walled carbon nanotubes@polydopamine‑carbon fiber/Polyphenylene sulfide (PVDF/MWCNTs@PDA-CF/PPS) solar evaporation film composed of a hydrophobic PVDF/MWCNTs layer and a PDA-modified CF/PPS fiber substrate with a hydrophilic three-dimensional gradient structure was investigated. The upper is coated with a hydrophobic solar-absorbing coating to ensure that the heat is concentrated in the photothermal layer. The lower is a unique three-dimensional gradient water delivery structure, which not only has an insulated water channel but also can continuously supply water, which will also limit the large volume of water contacting the photothermal layer, reducing the heat loss. PVDF/MWCNTs@PDA-CF/PPS exhibits high evaporation efficiency (1.24 kg m−2 h−1). This structural design will provide a promising solution to the global shortage of fresh water for desalination.