Toward multitasking solar desalination: a Janus and scalable paper evaporator with light trapping, heat confinement, salt resistance, and pollutant degradation

Solar-driven evaporators (SDEs) have attracted increasing attention in producing potable freshwater. Developing a multitasking SDE with stable self-floating performance, long-term salt resistance, effective heat management, pollutant degradation capability and good scalability for industrial production is significant but challenging. This work demonstrates the fabrication of a cellulose paper-based SDE with rough photothermal coating, controlled Janus wettability and a hierarchical Fenton catalyst for advanced solar desalination. Through the surface deposition of an urchin-like nanocatalyst and polypyrrole coating, a rough photothermal top layer for enhanced light trapping (98.6%) and a Fenton catalytic bottom layer for in situ pollutant degradation (98.1%) are constructed. Benzophenone-terminated polydimethylsiloxane is designed to realize facile asymmetric photo-grafting on porous paper, which further endows the evaporator with controlled Janus wettability, stable self-floating performance, long-term salt resistance, efficient heat management and rapid water transfer. Benefiting from such advantages, high solar-to-vapor efficiency (95.3%) and evaporation rate (1.88 kg m(-2) h(-1)) are obtained. This cellulose paper-based evaporator also exhibits mechanical flexibility, portability and cost-effectiveness. Furthermore, the preparation process, including simple deposition and cleaner photo-grafting, is feasible and scalable for industrial production. This work provides innovative concepts for developing advanced paper evaporators to realize multitasking solar desalination.