An autodriven, solar fuel collection for a highly compact, biomimetic-modified artificial leaf without membrane

Highlights: • A membrane-free gas separation method is invented for monolithic artificial leaf. • Buoyance force and biomimetic surface design is combined for gas bubble manipulation. • The collection efficiency of H₂ gas records over 90% with its high purity. • O₂ gas, counter product of water electrolysis shows very low cross-over with high purity. -- Abstract: Hydrogen fuel generation from water splitting has recently attracted much attention due to its high potential as a clean, renewable energy source. To obtain pure H₂ fuel, it is inevitably required to separate the H₂/O₂ product gas mixture, mainly relying on a membrane system at the current stage. However, this process has inherent durability and cost issues due to contamination, corrosion and its complex configuration. In our current work, we invented a highly compact gas separation and collection method in a water electrolysis system, which is set onto a biomimetically modified electrode without the use of a membrane or external convective flow. A key idea of this smart, compact and self-driven system is gas bubble manipulation by buoyant force and a slippery liquid infused porous surface (SLIPS). With the critical help of the biomimetic SLIPS wall by blocking bubble leakage, H₂ and O₂ product gases can be separately collected at the corresponding collection port. As a result, we achieved a remarkably improved H₂ collection value of over 90% with high purity using this membrane-free electrolysis system in which the product gases are separated only by their intrinsic buoyancy. This simple but effective gas separation/collection system is also applied to a highly compact, monolithic artificial leaf, in which the solar water splitting is practicably and conveniently conducted in a compact, floatable design.