Highly salt-resistant polypyrrole decorated waste mop sponge solar evaporator for efficient desalination

Interfacial solar desalination (ISE) emerges as a promising strategy to tackle the worldwide freshwater shortage. However, developing cost-effective solar evaporators that demonstrate exceptional evaporation rates while maintaining high salt-resistance is a tremendous challenge. This study introduces a three-dimensional (3D) solar evaporator, referred to as PPy-WMS, which is developed by employing a straightforward solution reaction to decorate polypyrrole (PPy) onto a waste mop sponge (WMS). The 3D PPy-WMS solar evaporator can capture ambient energy. When the exposure height is 6 cm, the PPy-WMS achieves an exceptional evaporation rate of 3.66 kg m−2 h−1 under 1-solar intensity. The macropore structure in WMS promotes water transport and facilitates salt ions backflow, resulting in high salt-resistance. The evaporation rate maintains at 2.91 kg m−2 h−1 when desalinating simulated seawater (20 wt%). Outdoor desalination experiments exhibit that 1 m2 of PPy-WMS can extract about 15 kg of freshwater per day. This economical and straightforwardly designed solar evaporator exhibits outstanding salt-resistance, presenting a viable remedy to address global freshwater scarcity.