Synergistic Effect of Neighboring Superhydrophilic Patterns on Superhydrophobic Surfaces for Enhanced Fog Collection.

In this work, a superhydrophobic surface loaded with elliptical superhydrophilic patterns in a V-shaped arrangement has been fabricated with the help of shape memory membranes with uniform vertically penetrative channels (i.e., SMEUVs, as a mask). The special geometry (elliptical) and arrangement (V-shaped) of superhydrophilic patterns play important roles in the enhancement of fog collection. The former not only facilitates droplet detachment from superhydrophilic regions but also dominates its directional transport. The latter promotes the coalescence of tiny droplets based on directional flow pathway toward collection area, minimizing the risk of re-evaporation of them and providing fresh sites for subsequent nucleation and growth of droplets. The combination of them contributes to the synergistic effect of neighboring superhydrophilic patterns on the superhydrophobic surface. As a result, the optimal specimen (V-shaped arrangement of elliptical superhydrophilic patterns) in this work exhibits much higher fog collection efficiency (∼4 times) relative to the reference (superhydrophobic or superhydrophilic surface). Our results are significant for the design and fabrication of fog collection systems.

Distance effect of single atoms on stability of cobalt oxide catalysts for acidic oxygen evolution.

Developing efficient and economical electrocatalysts for acidic oxygen evolution reaction (OER) is essential for proton exchange membrane water electrolyzers (PEMWE). Cobalt oxides are considered promising non-precious OER catalysts due to their high activities. However, the severe dissolution of Co atoms in acid media leads to the collapse of crystal structure, which impedes their application in PEMWE. Here, we report that introducing acid-resistant Ir single atoms into the lattice of spinel cobalt oxides can significantly suppress the Co dissolution and keep them highly stable during the acidic OER process. Combining theoretical and experimental studies, we reveal that the stabilizing effect induced by Ir heteroatoms exhibits a strong dependence on the distance of adjacent Ir single atoms, where the OER stability of cobalt oxides continuously improves with decreasing the distance. When the distance reduces to about 0.6 nm, the spinel cobalt oxides present no obvious degradation over a 60-h stability test for acidic OER, suggesting potential for practical applications.