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The reliable separation of some gases from others could be highly advantageous for a wide range of applications. For instance, it could help to produce hydrogen (H₂) for fuel cells and chemical applications or to capture the carbon dioxide (CO₂) emitted by industrial sites.

Many existing methods for separating gases rely on so-called gas separation membranes, thin films that allow specific gases to pass through them, while blocking others. One of the most promising materials for fabricating these membranes is graphene oxide (GO), a derivative of graphene that responds differently when exposed to distinct molecules.

Despite their potential for separating gases, conventional GO-based gas separation membranes suffer from low permeability. This essentially means that while they can separate H₂ or CO₂, gases move through them too slowly for them to be reliably deployed in real-world settings.

Researchers at the National University of Singapore recently introduced a new approach to creating crumpled GO membranes that exhibit both a higher H₂ permeability and selectivity (i.e., ability to distinguish between different gases). Their proposed method, outlined in a paper in Nature Nanotechnology, could facilitate the real-world use of these membranes to produce clean H₂ and capture gases that are harmful for the environment.

"This work emerged from a long-standing challenge in membrane science: the trade-off between selectivity and permeability in gas separation membranes," Daria V. Andreeva, senior author of the paper, told Tech Xplore. "GO has shown promise due to its tunable nanochannels, but its tightly stacked structure limits throughput.

"We were inspired to explore whether introducing controlled mechanical deformation, in our case, strain-induced crumpling, could reshape the internal architecture of GO membranes to overcome this bottleneck."

The main objective of this recent study by Andreeva and her colleagues was to re-design the transport pathways of GO membranes, which are different regions in GO through which specific gases pass. Ultimately, the researchers wished to achieve both a high permeability and selectivity, without adversely influencing the membranes' mechanical integrity and the extent to which they could be fabricated on a large-scale.

"We developed a method to crumple GO lamellas by applying uniaxial strain," explained Andreeva. "This process induces localized wrinkles and curvature across the membrane, creating a hierarchical network of nanoscopic voids and tortuous paths. These altered geometries allow small gas molecules like hydrogen to diffuse more rapidly, while still effectively blocking larger species."

The most notable advantage of the team's newly developed approach for engineering crumpled GO membranes is that it enables a high molecular sieving precision, while also increasing the flux of gas passing through them. This is a considerable achievement, as these two aspects were previously considered to be mutually exclusive.

In the future, the methods employed by Andreeva and her colleagues could be used to fabricate other GO-based membranes exhibiting even higher permeability and selectivity. Meanwhile, the researchers are working on further improving their membrane design and tailoring it for specific real-world applications.

"We are now exploring how to integrate this crumpling concept with stimuli-responsive materials to create dynamically reconfigurable membranes," added Andreeva. "We also plan to test these membranes under industrially relevant conditions and scale up their fabrication using roll-to-roll processes. In parallel, we are working with AI-guided design tools to identify other 2D materials that may benefit from similar structural engineering approaches."