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Abstract: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. A much sharper temperature gradient and more rapid increase of surface temperature were observed compared with the HCuPO-water dispersion in which the HCuPO particles were dispersed in water. Porous HCuPO-PDMS sheets were fabricated in order to further accelerate water evaporation. Under 808 nm laser irradiation with power density of 1000-2000 W.m(-2), water evaporation rate of salt water (3.5 wt %) was measured to be 1.13-1.85 kg.m(-2).h(-1) for porous floating HCuPO-PDMS, which was 2.2-3.6 times of that measured for ordinary salt water without HCuPO. By using a solar simulator as a light source, a very high solar thermal conversion efficiency of 63.6% was obtained with a power density of 1000 W.m(-2), indicating that solar evaporation of salt water could be greatly enhanced by the well-designed HCuPO.

Volume:121

Issue:1

Translation or Not:no