Three-dimensional disposable wooden chopsticks-derived solar-thermal evaporators for environmental energy-enhanced water evaporation and purification

Although solar steam generation is a sustainable and promising approach for generating clean water by purifying wastewater and desalinating seawater, its solar energy utilization efficiency and solar steam generation performance have to be improved further. Environmental energy-enhanced three-dimensional (3D) solar-thermal water evaporators are fabricated by decorating hydrophilic and porous disposable wooden chopsticks with black solar-thermal carbon nanotubes (CNTs) followed by assembling the CNT-decorated wooden chopsticks into a 3D array for efficient water evaporation and purification. The breaking of a chopstick creates 3D jagged fracture surface, increasing solar light absorption, enlarging evaporation area, and improving the water evaporation performance under downward solar light irradiation. The large sidewall of the chopsticks harvests environmental energy to accelerate water evaporation via thermal convection and radiation driven by the temperature gradient during the solar steam generation process. The CNT-decorated disposable chopstick evaporator with an exposed height of 4 cm achieves a remarkable evaporation rate of 3.70 kg m−2 h−1 and a high energy efficiency of 122.2 % under 1-sun irradiation, exhibiting application prospects in seawater desalination and wastewater purification.