Enhanced light trapping effect of hierarchical structure assembled from flower-like cobalt tetroxide and 3D-printed structure for efficient solar evaporation

Compared with conventional two-dimensional (2D) structure, three-dimensional (3D) solar steam generators have presented a considerably higher evaporation rate due to their structure superiority. As an emerging field, 3D printing technology has been attached by significant attention due to its feasibility and designability in the fabrication of micro-nano structures. Herein, inspired by natural light-trapping structures, a novel hierarchical structure assembled from flower-like cobalt tetroxide and 3D-printed stent is prepared. Based on the geometrical light trapping effect, both the flower-like structure in cobalt tetroxide and the hollow morphology in 3D-printed stent can significantly enhance the solar absorption and conversion efficiency through multiple reflection-incidence processes. Since the wetting direction in the cylindrical structure is always from the edge to the center, there will be a large number of salt particles at the edge of the cylinder falling by the virtue of gravity, thus achieving a high salt tolerance, and this process is illustrated by molecular dynamics simulation. Along with the rapid photo-thermal response in the solar spectrum, this 3D-printed hierarchical structure coated with flower-like cobalt tetroxide has achieved a high steam generation rate of 2.028 kg m-2h−1 under one sun irradiation (1.0 kW/m2) and excellent decontamination ability for organic dye-containing solution. Meanwhile, the desirable steam generation rate can maintain an average value of more than 1.8 kg·m-2h−1 for long time. This 3D-printed solar evaporator is highly efficient and salt-tolerant, attributed to the enhanced geometrical light-trapping and artificial channel-array structure, presenting an effective solution for enhancing solar absorption and conversion.