Constructing CoO Nanoneedle Hierarchical Structure Based on Cassie States for Highly Efficient Fog Harvesting

Inspired by the surface structure of cactus, CoO nanoneedle hierarchical structure was obtained by hydrothermal synthesis on the surface of copper mesh for fog collection. By adjusting the conditions of hydrothermal synthesis, the hierarchical structure with good orientation and moderate sparsity can maintain the Cassie state wetting model for a long time, which effectively promotes the falling speed of water droplets and improves the efficiency of fog collection. Collecting water from the fog becomes a promising strategy to address the water shortage. In this work, the CoO nanoneedle hierarchical structure was designed and prepared on the surface of the copper mesh by hydrothermal synthesis. The number of nanoclusters on the CoO nanoneedle array was changed by adjusting the mass concentration of the precursor solution. CoO nanoneedle array and nanoclusters form a hierarchical structure, which is conducive to the binding of air and the aggregation of water droplets. The results show that the surface of CoO nanoneedle hierarchical structure with good orientation and moderate sparsity has weak adhesion and stronger air binding capacity. Compared with other CoO nanoneedle structures, the hierarchical structure can effectively maintain the Cassie state wetting model for a long time, which improves the fog harvesting efficiency. This research offers a new strategy to design nanostructures for efficient fog collection, which has important implications on water harvesting from the air.