Solar-driven photothermal-evaporation coupling: antibacterial-evaporation integrated wood-based photothermal materials for seawater desalination

Abstract

Tackling the challenges of global freshwater scarcity and energy consumption, efficient solar powered seawater desalination strategies are needed. However, current interface evaporation technology is limited by insufficient photothermal conversion efficiency, unclear energy loss mechanisms, and high material costs. In this work, we report a highly efficient and stable wood-based photothermal composite material, which is constructed by in-situ growth of manganese dioxide (MnO2) nanoflowers on porous, low thermal conductivity poplar wood, combined with a blackening coating of iron tannic acid to construct Mn/wood@Fe-GA photothermal evaporation system. The three dimensional MnO2 structure enhances light harvesting while providing abundant active sites to stabilize Fe3+, synergizing with the wood's vertically aligned channels and low thermal conductivity to facilitate water transport and suppress heat loss. The composite achieves a high evaporation rate of 2.25 kg m−2 h−1 under 1.3 kW m−2 illumination and maintains a stable performance of 1.84–1.97 kg m−2 h−1 in 15% NaCl solution over extended operation. We demonstrate that the formed Mn–O bonds regulate the local chemical environment to inhibit salt crystallization, thereby ensuring long-term stability in seawater desalination. By elucidating the relationship between structural performance and evaporation mechanism, this work provides theoretical insights and practical approaches for sustainable, high-performance, and low-cost desalination of photothermal materials.