Porous solar evaporator with hierarchical photothermal structure for highly-performance desalination and water remediation

Interface solar-driven evaporation represents sustained solutions to global water shortages, with performance critically relying on photothermal conversion at the evaporation interface by photothermal materials. While conjugated and metal materials heterostructures enhance evaporation by light absorption and generate additional hot carriers, aggregation limits overall efficiency. Here, we report a porous aerogel with a hierarchical photothermal structure through integrating π conjugation and plasmon resonance effects of carboxylated multiwalled‑carbon nanotubes (MWCNTs-COOH), polypyrrole (PPy) and silver nanoparticles (AgNPs) on cellulose framework for high photothermal conversion efficiency. The conjugated system of MWCNTs-COOH/PPy contributes efficiency through efficient lattice vibrations and phonon-mediated thermalization. Whereas the localized surface plasmon resonance of highly dispersed AgNPs enables hot electron injection and narrows the bandgap (decreased by 14.5%). Hence, the aerogel demonstrated superior light absorption (>97%) and highly photothermal conversion efficiency (90.7%). Moreover, the hydrophilic nanochannels within the cellulose network facilitate the formation of intermediate water clusters and enable efficient evaporation. The aerogel showcases salt-tolerance with a self-cleaning mechanism. Benefiting from these synergistic effects, the as-prepared porous aerogel exhibits a high evaporation rate (3.06 kg m⁻² h⁻¹) and efficient removal rates (>99%) for inorganic salts and dyes, surpassing most of the state-of-the-art aerogel-based photothermal evaporators. Both purifying seawater and wastewater are below the World Health Organization (WHO) standards. The stability of outdoor field tests shows strong promise in application on a large scale. Moreover, outstanding antibacterial properties are attributed to the aerogel due to the incorporation of AgNPs. This work provides a paradigm for developing multi-mechanism synergistic systems achieving high-performance solar desalination.