Zwitterionic hydrogel coated superhydrophilic hierarchical antifouling floater enables unimpeded interfacial steam generation and multi-contamination resistance in complex conditions

Abstract

• A zwitterionic hydrogel coated evaporator is developed for solar steam generation. • The superhydrophilic surfaces and channels guarantee unimpeded water supply. • The evaporator possesses multi-contamination resistance to salt, oil, and biofouling. Continuous water pumping and steam generation are key factors in long-term solar-driven evaporation for fresh water production. However, current solar desalination devices easily get contaminated by salt accumulation, oil spill or marine fouling in real-world applications, causing blockage, corrosion or even invalidation. Developing antifouling coatings that can protect the devices from multi-contamination is a superior option to guarantee the longevity of the devices and stable fresh water generation. Herein, a superhydrophilic hierarchical antifouling floater (SHAF) consisted of zwitterionic hydrogel coated polyurethane (PU), polystyrene (PS) foam and cotton swabs, is developed. The porous PU fabric is competent to fragment water into ultra-fine droplets, increasing the vapor pressure and promoting the evaporation process. The zwitterionic coating can bind water molecules to form a hydration layer, thus leading to stable water transport and fascinating fouling resistance. Integrated with these merits, this SHAF accelerates water evaporation rate up to ~2.2 kg m −2 h −1 with a photothermal conversion efficiency of 93.5%. It also exhibits prominent microbial resistance with 96.2% against E. coli and ~100% against diatom. Additionally, due to the hydration shield induced by the zwitterionic coating, the SHAF surface is endowed with self-cleaning property even against crude oil pollution. Therefore, the SHAF with highly efficient water evaporation and multi-contamination resistance is a potential candidate for solar-driven fresh water production from seawater or even wastewater.