Boosted light absorption by WO_3-x/Ag/PbS heterostructure for high-efficiency interfacial solar steam generation

Interfacial solar steam generation is considered a promising approach to address energy and drinking water shortages. However, designing efficient light-absorbing and photothermal-converting materials remains challenging. In this study, we describe a detailed method for synthesising a three-dimensional (3D) hierarchical oxygen defect-rich WO₃/Ag/PbS/Ni foam (termed WO_3-x/Ag/PbS/NF) composite to realise efficient exciton separation and enhanced photothermal conversion. The 3D heterogeneous ternary photothermal material combines the individual benefits of WO_3-x, Ag and PbS, improving charge transfer and promoting photogenerated electron-hole pairs. This enhances light absorption and energy conversion. Theoretical calculations indicate that the increased photothermal conversion efficiency primarily results from the heterojunction between Ag, WO_3-x and PbS, facilitating exciton separation and electron transfer. Consequently, the WO_3-x/Ag/PbS/NF solar evaporator exhibits exceptional light absorption (98% within the sunlight spectrum), a high evaporation rate of 1.90 kg m^-2h^-1 under 1 sun and a light-to-heat conversion efficiency of 94%. The WO_3-x/Ag/PbS/NF evaporator also exhibits excellent capabilities in seawater desalination and wastewater treatment. This approach introduces a synergistic concept for creating novel multifunctional light-absorbing materials suitable for various energy-related applications.