Development of a High-Performance Solar-Driven Seawater Desalination System Using a Three-Dimensional Ionic PEC-T Hydrogel and a PEDOT/GO Photothermal Layer

 Solar vapor generation has emerged as a promising desalination technology because of its low energy consumption and sustainable use of solar energy. However, conventional hydrogel-based solar evaporators suffer from repeated swelling and salt accumulation under seawater conditions, resulting in poor mechanical stability and limited long-term durability.
 In this study, a three-dimensional anionic polymer (PSS-T) was introduced to replace conventional linear polyelectrolytes. A mechanically robust PEC-T hydrogel was fabricated through electrostatic interactions with a cationic polymer (PMPTC) and used as the supporting layer. A photothermal layer composed of poly(3,4-ethylenedioxythiophene) (PEDOT) and graphene oxide (GO) was constructed to improve solar absorption and photothermal conversion.  Among the prepared hydrogels, PEC-T50 exhibited the highest tensile strength and fracture stress. While the conventional PEC hydrogel showed excessive swelling of approximately 2200%, the PEC-T hydrogels exhibited much lower swelling ratios (160–570%). PEC-T50 also maintained its original morphology after 72 h of swelling and retained over 60% of its swelling capacity after five swelling–drying cycles, demonstrating excellent structural stability. The PEDOT:PEC-T50/GO photothermal layer containing 0.5wt% GO showed the best photothermal performance, reaching approximately 60°C under dry conditions and over 40°C during one-sun evaporation. The optimized evaporator achieved an evaporation rate of 2.25 kg·m⁻²·h⁻¹, higher than PEDOT:PEC-T(1.95 kg·m⁻²·h⁻¹) and PEDOT:PEC(1.74 kg·m⁻²·h⁻¹). It also maintained stable evaporation performance and structural integrity during an 8-day desalination test, demonstrating excellent long-term durability. These results indicate that the proposed PEDOT:PEC-T/GO platform is a promising candidate for efficient and durable solar-driven seawater desalination.