Emerging Material Design Trends in Photothermal Water Vapor Generation

Photothermal steam generators hold significant potential as sustainable and green technologies for applications such as water desalination, wastewater treatment, sterilization, and photothermal electric generation by efficiently harnessing solar energy to produce steam. However, their performance heavily depends on the precise design and optimization of advanced materials, which present notable challenges. Essential material properties include high solar light absorption, facilitated by enhanced crystallinity and nanostructured designs, low thermal conductivity achieved through defect engineering, and vacancy creation. Additionally, optimal wettability, supported by surface roughness and hydrophilicity, ensures efficient water transport to the evaporation interface. Salt resistivity, crucial for preventing performance degradation, is managed by controlling thermal gradients and employing strategies such as vertically aligned pores and a leaning structure for salt management. Floatability, achieved through reduced density and increased porosity, is also essential for maintaining high system efficiency. Integrating these diverse properties into a single material system requires a delicate balance of optical, thermal, and mechanical characteristics, along with long–term durability. This review outlines the key material attributes driving the performance of photothermal steam generators, explores recent advances in material design, and proposes strategies to overcome existing challenges. Furthermore, it assesses the technology readiness levels (TRLs) of these systems, identifying areas for future development to improve their practical feasibility.