Solar-driven watersteam/brine production and brine-driven electricity generation by photothermal fabric coupled with osmotic membrane

Abstract

The combination of solar-driven seawater evaporation and electricity generation has received increasing attention, and the traditional routes are based on the combination of the evaporator with thermogalvanic cells, thermoelectric or hydrovoltaic modules. But these combinations are relatively complex, and solid salt will crystallize during long-term seawater evaporation, limiting their practical applications. To solve the above problems, herein we have proposed a new kind of evaporation/electricity generation device by combining the photothermal fabric hanging-model evaporator and osmotic membrane-based generator. As a model of photothermal fabric, cotton fabric has been dyed with Chinese ink, and then the cotton-carbon fabric has high hydrophilicity and excellent photoabsorption efficiency (97.1%). Subsequently, the cotton-carbon fabric is set in an arc-shaped design between two seawater tanks for the construction of the hanging-model evaporator. Under the illumination of one sun, the evaporation rate of the hanging-model evaporator is as high as 1.94 kg m−2 h−1 without solid-salt accumulation, and the high-concentration brine (Na+ concentration: 1.07 ×105 mg L−1) can drip from the fabric bottom, realizing solar-driven watersteam and brine production with standing stability. Simultaneously, the brine is separated from the original seawater by a commercial cation exchange membrane, and two Ag/AgCl electrodes are used to construct an osmotic generator. It shows a high open voltage of 52 mV and the highest output power density of 116.52 mW m−2. Therefore, the present integration of the hanging-model evaporator and osmotic generator establishes a new path to continuously produce watersteam and brine under the sun and then to confer brine-driven electricity generation.