Solar-driven interfacial evaporation is a sustainable technology for freshwater production; however, the rational design of photothermal materials that simultaneously achieve full-spectrum solar absorption, minimized thermal loss, and efficient energy utilization remains a formidable challenge. Herein, we report a “post-treatment” defect engineering strategy to fabricate highly active, non-stoichiometric BTO (black TiO2−x) via a hydrothermal-assisted atmospheric deoxygenation process. The precise modulation of oxygen vacancies (Ov) within the TiO2 lattice effectively narrows its bandgap, facilitating a dramatic enhancement in both light-harvesting capacity and photothermal conversion efficiency. By integrating the BTO into a polyvinyl alcohol (PVA) hydrogel framework, we developed a 3D evaporator (TPVA) that synergistically couples superior optical trapping with attenuated thermal conductivity. Consequently, the Ov-enriched TPVA architecture achieves an impressive solar absorption of 94.3%, enabling a high-performance evaporation rate of 2.492 kg m−2 h−1 under 1 sun irradiation, which is approximately 5.0 times higher than that of direct seawater evaporation under the same conditions. This work underscores the efficacy of defect engineering in optimizing semiconductor photothermal materials and provides a promising strategy for the advancement of next-generation solar desalination technologies.
Zhang et al. (2026) studied this question.