Synergy of Light Trapping and Water Management in Interconnected Porous PEDOT:PSS Hydrogels for Efficient Solar-Driven Water Purification

Abstract

Interfacial solar water purification is emerging as a sustainable and environmental-friendly approach for solar energy harvesting and clean water production. Currently, the limited photothermal conversion efficiency restricts its practical applications. Developing evaporators with porous structures has been proposed as a promising way toward boosting solar-thermal-vapor conversion by enhancing energy utilization and evaporation area. However, effective collaboration between light capture and water management of porous evaporators is the main challenge for efficient freshwater production. Here, we reported a pure poly­(3,4-ethylenedioxythiophene) (PEDOT):polystyrene sulfonate (PSS) hydrogel by in situ polymerization as a solar evaporator for water purification from saline water or wastewater. The interconnected and microporous structure of the PEDOT:PSS hydrogel (PPH) can dramatically trap light throughout broad incident angles as well as increase the active water content simultaneously, which is highly controlled by the PSS content. The PPH could efficiently convert the absorbed solar energy and wastewater into fresh water, thus leading to an excellent photothermal conversion efficiency of 96.4% and an evaporation rate of 2.43 kg·m–2·h–1 during purification of 3.5 wt % NaCl brine under one sun irradiation. This PPH exhibits sustainable and stable performance in 88 h when purified with 3.5 wt % simulated saline water, with an evaporation rate of ∼2.32 kg·m–2·h–1. What is more, this PPH performs satisfied performance in water purification (with the concentration of all ions dropping below 1 mg·L–1) from saline water, dye, and heavy metal wastewater. These results demonstrate that high evaporation performance could be achieved if effective light trapping and water management are ensured simultaneously. Thus, this study provides a new possibility for long-term, stable, and efficient water purification from wastewater.

A Core–Shell Structured Hydrogel Sponge for Efficient and Long-Term Solar Evaporation

“…In conjunction with the conclusion in Section , excessive formation of PEDOT occurs within the composite sponge-like hydrogel when the polymerization time is excessively long, rendering these PEDOT particles ineffective for photothermal conversion. Additionally, due to PEDOT’s hydrophobic nature, it reduces water transfer efficiency within the composite sponge-like hydrogel and subsequently affects its water evaporation rate. , Further extending the polymerization time to 12 and 24 h, it can be found that the water evaporation rate drops further to 2.37 and 2.03 kg/m 2 h. Meanwhile, high light intensity prompts steam generation for SPH-6, as shown in Figure S7. The evaporation rates reached 3.76 and 4.58 kg/m 2 h under 1.5 and 2 sun illumination, respectively .…”