Growth of phosphomolybdate-carbon hybrid nanorod array on carbon-fiber cloth with enhanced light-trapping and decreased water-evaporation enthalpy for constructing efficient salt-free hanging evaporator

Abstract

Although numerous photothermal materials have been designed for solar-enabled water evaporation, their use in practical applications remains challenging due to their unsatisfactory photoabsorption, high vaporization enthalpy and serious salt crystallization phenomenon. To overcome these issues, herein we have reported the growth of phosphomolybdate-carbon (PMo12-C) hybrid nanorod arrays on carbon-fiber cloth (CFc) for constructing the efficient salt-free hanging evaporator. The optimized CFc/PMo12-C with nanorods (diameter: ∼0.5 μm, length: ∼1.8 μm) exhibits increased photo-absorption (93.1 %) in the range of 280–2500 nm due to nanorod-induced light-trapping effects, and they also have the decreased water-evaporation enthalpy (2066.7 kJ/kg, 36.8 °C) owing to the disorganization of the hydrogen bonds at nanorods/water interface. Subsequently, such CFc/PMo12-C is hanging between one high seawater-tank and one low empty-tank to construct the incline-hanging model evaporator, where seawater (3.5 wt% NaCl) can infiltrate and then flow from high to low along CFc/PMo12-C. Upon irradiation with sunlight (1.0 kW m−2), the evaporator exhibits a high evaporation rate (2.12 kg m−2 h−1). Even for high salt concentration (21.0 wt% NaCl solution), the hanging CFc/PMo12-C evaporator can retain an almost unchanged evaporation rate (∼2.1 kg m−2 h−1) and present excellent salt-resistant performance with 8 h irradiation. Therefore, this work not only offers a new approach for preparing PMo12-C hybrid nanorod array on CFc but also realizes the efficient continuous seawater evaporation without solid-salt accumulation.