Salt-resistant carbon dots modified solar steam system enhanced by chemical advection

Abstract Salt deposition still remains a significant challenge due to the decreasing evaporation efficiency of solar desalination. Herein, we provide a salt-rejection model coupled with the experimental verification about the chemical diffusion or advection process for solar steam generation. The designed evaporating system established by in-situ polymerization (polypyrrole) of carbon dots modified MnO2 nanowires coated on non-woven cotton fabric decorated ultra-flexible and super hydrophilic polyurethane foam (30 % wicking). The salt-rejection investigations reveal real-time chemical advection phenomena where hot brine flows from the top surface to underneath water through a salinity gradient with the aid of accumulated heat. The prototype demonstrates an excellent salt rejection ability within a minimum record time (2g/100 minutes) or once soaked (2g/60 seconds). The floatable solar-driven evaporator exhibits incredible flexibility (80%, compressive strain) along with an evaporation rate of 1.68 kg m-2 h-1, and photothermal conversion efficiency (∼96.4%, solar to vapor) from high-salinity brine (10 wt %) and wastewater containing heavy metal ions (30 wt%). The outdoor test revealed a yield of 13.60 kg m-2 in one sunny day that provides a potential solution to single-step drinking water supply from various resources of the sea, lakes, and mixtures of emulsified oil, bacterial pathogens, and industrial wastewater.