Design of poly(3,4-ethylenedioxythiophene): polystyrene sulfonate-polyacrylamide dual network hydrogel for long-term stable, highly efficient solar steam generation

Photothermal materials have attracted significant interests for interfacial solar steam generation towards desalination or sewage purification. However, despite recent encouraging progress, the development of long-term stable photothermal materials with high overall performance is still one of the major hurdles to realize scalable practical usage. Herein, we develop a dual network hydrogel of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and polyacrylamide (PAAm) for interfacial solar steam generation via one-step radical polymerization and chemical cross-linking of acrylamide within viscous PEDOT:PSS nanofibril dispersion. As-obtained PEDOT:PSS-PAAm hydrogel exhibits a unique combination of advantageous evaporation performances including excellent sunlight absorption (∼99.8%), fast steam generation rate (2.15 kg m-2 h-1), and high energy efficiency (∼97.2%), comparable to the state-of-the-art photothermal materials. Furthermore, the PEDOT:PSS-PAAm hydrogel also displays fascinating mechanical properties like softness (Young’s modulus: 38 ∼ 86 kPa), stretchability (fracture strain: >80%), and nice mechanical stability against varying deformations, guaranteeing its potential usage in harsh practical application environment. Toward real water purification applications, such a hydrogel is demonstrated to possess excellent long-term stability with an average energy efficiency of 94.8% and anti-salt-fouling properties against 30-day continuous outdoor exposure, superior to most previously reported photothermal materials. We further demonstrate PEDOT:PSS-PAAm hydrogel-integrated solar steam generator for practical desalination and sewage purification, and the generated water can reach the WHO drinking water standards for metal cations/organic pollutants.