TiO₂ Decorated onto Three-Dimensional Carbonized Osmanthus Fragrans Leaves for Solar-Driven Clean Water Generation

Solar steam generation (SSG) has garnered significant attention for its potential in water purification applications. While composites with physically combined structures based on semiconductors or biomass have been developed for SSG, there remains a critical need for low-cost, high-efficiency devices. In this study, TiO₂ composites exhibiting excellent stability, high solar absorption, porous microstructure, and hydrophilic surfaces were identified as effective materials for SSG and water purification for the first time. A novel SSG device was designed by decorating TiO₂ onto three-dimensional carbonized Osmanthus fragrans leaves (TiO₂/carbonized OFL). Compared to directly carbonized OFL (without TiO₂) and Osmanthus fragrans leaves with templated TiO₂ (OFL-templated TiO₂), the TiO₂/carbonized OFL carbon composites demonstrated enhanced solar absorption, achieving over 99% in the visible region and more than 80% in the near-infrared region. Under solar illumination of 1 kW·m^-2, the TiO₂/carbonized OFL device achieved a high water evaporation rate of 2.31 kg·m^-2·h^-1, which is 1.6 times higher than that of carbonized OFL and 3.45 times higher than OFL-templated TiO₂. Additionally, the TiO₂/carbonized OFL system exhibited remarkable efficiency in treating pharmaceutical wastewater, with a chemical oxygen demand (COD) removal efficiency of 98.9% and an ammonia nitrogen removal efficiency of 90.8% under solar radiation.