Photothermal-photocatalytic bifunctional highly porous hydrogel for efficient coherent sewage purification-clean water generation

Abstract

Solar interfacial water evaporation based on photothermal materials presents great potential in tackling global water scarcity and environmental pollution. However, existing photothermal materials still suffer from performance deficiencies like insufficient evaporation rate and unreliable long-term stability, as well as single-function limitations leading to incomplete removal of contaminants from wastewater, severely hindering their practical applications. Herein, we develop a novel, cost-effective, highly porous hydrogel composite integrated with synchronous photothermal and photocatalytic effects by a facile two-step immobilization approach. This method involves an initial sonication-induced pre-polymerization of acrylamide to produce a viscous solution that uniformly disperses TiO₂ nanoparticles and single-walled carbon nanotubes (SWCNTs), followed by a secondary in-situ free radical polymerization to achieve stable homogeneous TiO₂/SWCNTs/polyacrylamide (PAM) hydrogel composite with an ultrahigh porosity of 88.40 %. Remarkably, the resultant hydrogel composite simultaneously exhibits excellent bifunctional photothermal and photocatalytic performances, including exceptional sunlight absorption of 99.35 %, high evaporation rate of 3.53 kg m⁻² h⁻¹, and high photodegradation efficiency of 84.27 % for methylene blue. Furthermore, the water evaporator fabricated with such hydrogel demonstrates consistent desalination performance over 40-day continuous monitoring with salt ion removal rates over 95 %, positioning it as a promising bifunctional material for coherent sewage purification and clean water generation.