Room-temperature Graphene Ripple Adsorption Stably Crystallizes Xenon, Krypton, Argon, and Helium Gases

The challenge of efficiently adsorbing nonpolar gases, especially noble gases, at room temperature and atmospheric pressure has long hindered advancements in gas storage and separation technologies. Now, Weilin Liu, Xianlei Huang, Li-Guo Dou, alongside colleagues from multiple institutions including Qianglong Fang and Ang Li, have demonstrated stable adsorption of noble gases, xenon, krypton, argon, and helium, onto highly rippled graphene at room temperature. Through both theoretical simulations and experimental verification, the team confirmed that the curvature of the graphene significantly enhances adsorption, allowing for stable capture of these gases. The adsorbed atoms arrange themselves in a crystalline structure and remain stable until desorbed at approximately 350°C, without damaging the graphene lattice. This ripple-assisted adsorption not only redefines the theoretical understanding of gas adsorption but also opens doors for advancements in gas storage, separation, catalysis, and surface modification technologies.

Noble Gas Adsorption on 2D Materials

Researchers have investigated the adsorption of noble gases, argon, krypton, and helium, onto two-dimensional materials like graphene, molybdenum disulfide, and niobium diselenide, and even carbon nanotubes. This work focuses on how adsorption alters the materials’ electronic and structural characteristics, and importantly, whether this process is stable and reversible. The team employed advanced techniques to understand these interactions and their potential applications. Detailed structural characterization using Raman spectroscopy and atomic force microscopy confirms that gas adsorption introduces defects into the materials’ lattices.

Raman spectroscopy tracks both adsorption and desorption, demonstrating structural recovery after heating, and confirms the stability of the adsorbed gases under vacuum conditions. Electronic characterization, including scanning tunneling spectroscopy and X-ray photoelectron spectroscopy, reveals further changes. Scanning tunneling spectroscopy demonstrates the opening of a band gap in graphene upon gas adsorption, indicating a shift in its electronic structure. Electrical transport measurements show that adsorbed gases can act as dopants, altering the material’s conductivity. Complementary theoretical calculations using density functional theory model the electronic structure of rippled graphene with adsorbed gases, explaining experimental observations and predicting material behaviour.

The research demonstrates that graphene exhibits strong adsorption capabilities, with the process being both reversible and repeatable. Similar phenomena are observed on other 2D materials like molybdenum disulfide and niobium diselenide, although the effects may be less pronounced. The team’s findings suggest that gas adsorption can tune the electronic properties of 2D materials, potentially enabling applications in sensors and electronic devices.

Plasma Adsorption Stabilizes Noble Gases on Graphene

Scientists have achieved stable adsorption of noble gases, xenon, krypton, argon, and helium, on graphene at room temperature, a significant advancement in gas adsorption research. The team pioneered a technique employing weakly ionized plasma to deposit the gases onto graphene films supported by copper and suspended graphene membranes, preserving the integrity of the graphene lattice for stable adsorption and subsequent desorption. Scanning tunnelling microscopy images reveal that xenon atoms crystallize into domains exhibiting a closest-packed structure with a lateral distance of approximately 6. 8 Å between neighbouring atoms, adapting to the underlying graphene honeycomb lattice.

By adjusting the bias voltage during imaging, scientists observed changes in the xenon lattice arrangement while enhancing the visibility of the graphene lattice. X-ray photoelectron spectroscopy confirms the presence of xenon, providing evidence of successful adsorption. The team extended this work to argon and helium, observing irregular domains formed by adsorbed atoms, often arranged in dimer configurations. Scanning tunnelling spectroscopy measurements of the adsorbed xenon and argon reveal distinct spectral features, similar to those observed with adsorbed gases on gold at extremely low temperatures, and a small bandgap emerges in xenon-adsorbed graphene. Selected area electron diffraction patterns collected from suspended graphene with adsorbed xenon demonstrate the formation of crystalline xenon structures aligned with the underlying graphene lattice.

Rippled Graphene Captures Noble Gases at Room Temperature

Scientists have demonstrated the stable adsorption of noble gases, xenon, krypton, argon, and helium, on rippled graphene at room temperature, overcoming a long-standing challenge in materials science. This work establishes a new method for capturing these gases without the need for extremely low temperatures. The research team utilized both theoretical simulations and experimental observations to confirm the successful capture and crystallization of noble gas atoms on the graphene surface. Theoretical calculations reveal that the adsorption energy of argon on flat graphene is insufficient for stable capture, but increases significantly as the curvature of graphene ripples increases.

This trend holds true for all noble gases studied, with heavier gases like xenon exhibiting even stronger adsorption. These calculations confirm that increased ripple curvature directly correlates with enhanced gas capture. Experiments utilizing scanning tunnelling microscopy provide direct visualization of the adsorbed gases. Large-scale images show the formation of irregular domains composed of crystallized xenon atoms on the graphene surface. Detailed analysis reveals a closest-packed structure with a lateral distance of approximately 6.

8 Å between neighbouring xenon atoms, exhibiting a structural symmetry that transitions from six-fold to two-fold. X-ray photoelectron spectroscopy confirms the presence of xenon by detecting characteristic core level peaks. The adsorbed gases can be completely desorbed by annealing the graphene to approximately 350°C without damaging the underlying lattice.

Noble Gas Adsorption on Rippled Graphene Surfaces

This research demonstrates stable adsorption of noble gases, xenon, krypton, argon, and helium, on rippled graphene at room temperature, a significant achievement given the challenges of adsorbing nonpolar gases under these conditions. Through experimental techniques, including electron energy loss spectroscopy and X-ray photoelectron spectroscopy, researchers confirmed that the adsorbed gas atoms crystallize into periodically arranged structures on the graphene surface, exhibiting high stability for extended periods and can be fully desorbed at approximately 350°C without damaging the graphene lattice, which fully recovers its original properties. The team extended these findings to other layered materials, such as niobium diselenide, molybdenum disulfide, and single-walled carbon nanotubes, indicating the broad applicability of this ripple-assisted adsorption mechanism. Adsorption modifies the structural and physical properties of these materials, influencing electrical transport, superconductivity, and Raman spectra, with complete recovery of these properties upon desorption. This work establishes a new approach to gas adsorption, differing from conventional physisorption and chemisorption, and promises to accelerate advancements in gas storage, separation technologies, catalysis, and surface modification.