Iron-catalyzed laser-induced graphene on cellulose paper for solar-driven interfacial evaporation

Solar-driven interfacial evaporation has emerged as a promising strategy to produce freshwater <i>via</i> seawater desalination. While cellulose-based photothermal materials have garnered significant attention in solar steam generation, conventional surface modification techniques (<i>e.g.</i>, coating and carbonization) often suffer from cumbersome preparation and limited design flexibility. This study pioneers a non-destructive laser-processing strategy to simultaneously induce spatially controlled graphene domains and iron oxide nanostructures on chemically modified cellulose matrices. Through synergistic integration of broadband light absorption (∼93.28% solar-weighted absorptance) with hierarchical water channels, the two-dimensional evaporator achieves exceptional evaporation performance (1.62 kg m^-2 h^-1, 99.0% efficiency) under 1 sun irradiation. Remarkably, the evaporation performance increases to 1.82 kg m^-2 h^-1 when configured into a three-dimensional architecture <i>via</i> simple single folding. Detailed characterizations reveal that laser-induced carbothermal reduction generates iron oxide-graphene composites as light absorbers, while preserving cellulose's inherent hydrophilicity for rapid capillary pumping. Notably, the engineered architecture demonstrates enhanced mechanical robustness (234% improvement in tensile strength) and programmable foldability, expanding applicability across diverse desalination scenarios. This laser-direct-writing paradigm establishes a sustainable pathway for developing next-generation cellulose-based solar evaporators.