Turning Corn Stalk Trashes into a Photothermal Agent for Interfacial Solar Water Evaporation for Sustainable Water Purification

Biomass‐based photothermal materials have a higher photothermal conversion efficiency and contribute significantly to improved solar water evaporation systems. This work aims to transform corn stalk (CS) trash into efficient photothermal materials with centralized and less‐contact area water supply systems to achieve enhanced interfacial heat accumulation. We successfully synthesized cornstalk biochar synthesized via pyrolysis to maintain the environmental concern and is deposited onto a scalable, and cost‐effective (<1$) polyurethane foam (triangle shape, where the tip plays the wick and centralized water supply). The detailed characterizations validate the porous structure of CS biochar‐coated PU foam (CSB@PU), and enhance interfacial heat accumulation up to 47.8 °C under 1 kW m −2 solar irradiation which is endowed via thermal management of polystyrene foam (PS). This reproducible interfacial heat accumulation and sustainable evaporator bestow a water evaporation rate of up to 1.38 kg m −2 h −1 , and solar‐to‐vapor conversion efficiency (84%) under one sun which is more efficient than other biomass‐derived evaporators. Inductively coupled plasma‐optical emission spectroscopy analysis validates the reductions of primary (Na + , K + , Mg 2+ , and Ca 2+ ) and heavy metal ion (Fe 3+ , Hg 2+ , Cd 2+ , and Pb 2+ ) concentrations in condensate, insights the potential of CSB@PU to advance the water treatment technologies.