Designing a Novel Photothermal Material of Hierarchical Microstructured Copper Phosphate for Solar Evaporation Enhancement

Hierarchical microstructured copper phosphate (HCuPO), which could accelerate water evaporation was well designed based on d–d transition of 3d electrons in Cu2+ and fabricated via a solvothermal method. A very strong vis–NIR absorption with the maximum at 808 nm was observed for the HCuPO. Upon irradiation of 808 nm NIR laser light, the HCuPO generated heat with a light-to-heat converting efficiency of 41.8%. The reason for this high efficiency was investigated and assigned to a high probability of nonradiative relaxation, which released the energy in form of heat, happened to the excited 3d electrons of Cu2+. The proposed photothermal mechanism was quite different from the surface–plasmon mechanism of other Cu-based photothermal materials. By adding HCuPO into polydimethylsiloxane (PDMS), HCuPO–PDMS composite sheets were fabricated. Due to the intrinsic hydrophobicity of PDMS matrix, the sheets were floatable on water surface and the heat generated by HCuPO was confined within water–air interface region...