Clean water harvesting and power generation by solar-absorbing Germanium@k-carrageenan evaporator demonstrating superior energy conversion

The deterioration of climate exacerbates the freshwater crisis. Solar-thermal interfacial evaporation, using sunlight as a driving energy source, is a promising approach to provide an effective solution to freshwater shortages. However, the low energy conversion efficiency and expensive evaporator manufacturing are still to be resolved. Herein, a strategy of clean water harvesting by solar-absorbing germanium@k-carrageenan (Ge@CA) evaporator demonstrating superior energy conversion is proposed. The Ge nanoparticles exhibit a significant solar absorption of 92.33% to achieve efficient solar-thermal conversion. The CA hydrogel provides three-dimensional water transmission channels to the evaporating surface. Meanwhile, the Ge nanoparticles can be fabricated by a facile ball-milling method. The CA as a cheap biomass can be easily interacted with KCl to obtain the porous hydrogel. Taking the advantages of Ge nanoparticles and CA hydrogel, the Janus-type Ge@CA hydrogel evaporator can achieve an evaporation rate of 2.88 kg m −2 ·h −1 and a solar-vapor conversion efficiency of 82.65% under 1 sun irradiation. Furthermore, the evaporator can produce thermoelectricity with the output voltage of 140.95 mV and the short-circuit current of 13.32 mA, yielding a power of 1.17 W m −2 . This reported solar device has huge potential for cutting-edge solar harvesting and usage.