Coal tar pitch porous carbon-based bimolecular crosslinked hydrogel evaporator for solar-driven efficient water purification

Hydrogel evaporators have been widely used in solar-driven interfacial water evaporation due to their good thermal insulation, strong hydrophilicity, and rich internal pores. However, the occlusion pores in the hydrogel with a single molecule chain not only limit water transportation but also lead to serious salt crystallization. Hence, we developed a hydrogel evaporator (NSC-PVA/8CMC) with an abundant and open pore structure by cross-linking polyvinyl alcohol (PVA) and carboxymethyl cellulose (CMC). In which, the low-cost amorphous coal tar pitch porous carbon (NSC) is used to absorb light and improve light-to-heat conversion. The porous structure and thermal insulation (0.37 W m⁻¹ K⁻¹) of NSC-PVA/8CMC are conducive to excellent light absorption (≈99.02 %) and minimizing heat loss, finally leading to excellent photothermal conversion (1.44 kg m⁻² h⁻¹, 72.96 %, 1 sun). More significantly, NSC-PVA/8CMC with a strong desalination capacity can provide a self-purifying performance in seawater and brackish water. At the same time, the innovative attempt to use coal tar pitch as the photothermal conversion material has expanded the application scope of coal tar pitch.