Fog Harvesting Based On Oxide Nano-tip Structure

Up to now,water shortage has become a global concern,seriously affecting people's lives and work,and even in some remote areas,it has already affected people's lives.Therefore,how to effectively collect available water resources from common fog is of great significance.Scientists have found that the macroscopic gradient structure facilitates the collection of fog due to the ability of its tip to help pin droplets and efficiently turn fog into droplets.However,the problem of the rapid falling of the collected water droplets still needs to be solved urgently.In this paper,inspired by the gradient structure,the Cu mesh is used as the substrate to grow ZnO,CoO and CuO nanoneedles structures on the surface.The nanoneedles can pin droplets quickly and in a large area,and has super air restraint ability.Achieved efficient fog collection performance,explored the wetting behavior and fog collection performance of different surfaces,and studied the movement of droplets on the microstructure surface and its mechanism.Firstly,ZnO nanostructures were prepared by two-step solution method with electric field assisted growth.The fog collection efficiency of ZnO nanorods and ZnO nanoneedles was compared,and it was found that the water collection efficiency of ZnO nanoneedles was 2149 mg/cm~2?2 min,which is obvious that water collection efficiency of ZnO nanoneedles is higher than that of ZnO nanorods.This is mainly because the nanoneedle can quickly gather fog into water droplets,thereby improving the fog collection efficiency;comparing the fog collection performance of ZnO nanoneedles and ZnO nanoneedle multistage structure,it is found that the fog collection efficiency of ZnO nanoneedle multistage structure within 2 min is 2708mg/cm~2.Further analysis shows that the multistage structure can better confine the air and keep small droplets falling quickly.Secondly,the CoO nanoneedles were prepared by hydrothermal synthesis method to change the uniformity of the nanoflower-cluster structure on the CoO nanoneedles.Analyzing the influence of the distribution of nanoflower-clusters on the fog collection performance,it was found that the more nanoflower-clusters,the better the fog collection performance,the highest can reach 2781 mg/cm~2?2 min.The results show that the nanoflower-clusters can confine the air well,maintain the Cassie state wetting mode,and then extend the time for the water droplets to roll down in a small size.Finally,the CuO nanowire-clusters with good binding force were grown in situ by the one-step oxidation method on the Cu mesh to study its fog collection performance;the obvious gradient structure of the CuO nanowire-clusters gave it a strong air-binding ability and promoted small droplets fall quickly to collect the fog efficiently,and the maximum can reach 2860 mg/cm~2in 2 minutes.This shows that maintaining the Cassie state wetting mode of the sample surface is a key factor in improving fog collection.