Rattan-based Janus evaporator decorated with dense arrays for efficient light harvesting and broad-spectrum solar absorption

Solar-driven interfacial evaporation is an effective solution to alleviate the global freshwater crisis. In this work, hydrophilic biomass-derived rattan was used as the substrate, with Ti2O3 and carbon nanoparticles spray-coated onto its surface without employing complex carbonization processes. Owing to the difference in hydrophilicity between these two photothermal materials, a synergistic effect led to the formation of microcone array structures on the rattan surface. This array structure prolongs the residence time of light, enhancing light harvesting while increasing the evaporation area. The hybrid coating combines the pronounced light absorption of Ti2O3 and carbon. This synergy enables broad-spectrum light absorption, reaching up to 95.97 %. Subsequently, a layer of polydimethylsiloxane (PDMS) was coated, and the hydrophobicity imparted by PDMS combined with the hydrophilicity of the rattan substrate formed a Janus structure. Under one-sun illumination, the Janus evaporator exhibited excellent freshwater output (2.39 kg m−2 h−1) and a photothermal conversion efficiency of 93.42 %. It achieved over 99 % purification efficiency for heavy metal ions, organic dyes, and saline solutions. Importantly, it demonstrated high stability in evaporation and salt resistance in real seawater. This low-cost and environmentally friendly evaporator offers novel insights for efficient light harvesting, demonstrating high application value and great potential in practical seawater desalination.