3D-printed hierarchical porous cellulose/alginate/carbon black hydrogel for high-efficiency solar steam generation

Solar steam generation (SSG) has great application prospects in seawater desalination and dye wastewater treatment. However, it is still a challenge to realize a low-cost, rapid evaporation, high water quality and sustainable solar-driven water purification system. Three-dimensional (3D) structural design of evaporator is conducive to promoting evaporation efficiency, which has great potential in SSG field. In this study, 3D hierarchical porous hybrid hydrogel evaporators with embedded carbon black (CB) for SSG are built through 3D printing method. The 3D hierarchically porous cellulose/alginate/carbon black hydrogel (CACH) shows a super-hydrophilic wettability, and excellent light absorption (97%) within the wavelength range from 300 to 2500 nm, which can dramatically improve water transportation capacity and photothermal performance in the evaporator. The evaporation rate of the evaporator is as high as 1.33 kg m-2h−1 and the conversion efficiency of solar energy at 1 kW m−2 (one-sun) solar illumination is up to 90.6%. Moreover, the evaporation also exhibits superior salt resistant performance, and collected water meets World Health Organization (WHO) drinking water standards after purification from seawater. In addition, a small amount of photothermal material (1 wt% CB) is required in this system, which is beneficial to reduce the cost of the system. The 3D-printed hierarchically porous hydrogel evaporator has great application prospects in seawater desalination and wastewater purification.