Sandwich-Structured Copper Foam with Long-Range Bubble Transport Enables Efficient Water Splitting and Pure Bubble Harvesting.

Achieving long-range bubble transport in liquid is crucial to enable high-efficiency water splitting and bubble harvesting. This study presents a simple and effective method for fabricating a unique sandwich-structured material with aerophobic/aerophilic/aerophobic symmetric wettability. The design of this structure ensures that bubbles move unidirectionally from the aerophobic regions on either side into the central aerophilic channel, while the reverse passage through the copper foam is prevented. Furthermore, experimental results demonstrate that the unique structure enables versatile underwater bubble transport behaviors, including wave-like and spiral paths, thereby facilitating long-range, efficient directional movement. This long-range, spontaneous, and directional pumpless transport of underwater bubbles allows for efficient water splitting. Combining experimental results with theoretical calculations, the unique structure effectively mitigates H2 (hydrogen) bubble accumulation on the electrode surface, thereby promoting efficient mass transfer during electrolysis. Moreover, its superior bubble transport capability enables efficient bubble collection, even in complex environments, making it highly suitable for gas-related applications.