A photothermal hydrogel-fabric architected with polyvinyl alcohol decorated polypyrrole nanoparticles for efficient brine distillation

Herein, water-dispersible polypyrrole (PPy)-based nanoparticles were synthesised from polyvinyl alcohol (PVA) via acetalization with pyrrole-2-carboxaldehyde and in situ graft redox polymerization of pyrrole. The PVA decorated PPy nanoparticles were facilely anchored onto cotton fabric via drop-casting and borate-crosslinking to form a robust photothermal hydrogel-fabric (PHF). The new PHF material achieves strong sunlight absorption capacity (>92 %) and high evaporation rate (1.62 kg m–2h−1) of pure water on 2D platform under 1-sun irradiation. Further, a self-floating 3D evaporator (3D-PHF) was constructed by wrapping the PHF material on an expanded polyethylene cylinder, which unexpectedly exhibits high evaporation rate from pure water (2.03 kg m–2h−1) and brines with different concentrations (1.95 kg m–2h−1 for 3.5- wt% and 1.85 kg m–2h−1 for 10- wt%). Cumulative 100 h long-time evaporation confirms the 3D-PHF evaporator even maintained a stable evaporation efficacy to 20- wt% brine (1.55 kg m–2h−1) due to its self-renewal features triggered by the gravity of deposited salt on upper surface. This study paves a simple pathway to architect novel photothermal material with good solar evaporation efficacy, which contributes to the applications of solar evaporation to saline water treatment.