growing role.
Both fuels are mainly made of methane, which burns more cleanly than coal or oil and is widely used for heating, electricity generation and chemical manufacturing. However, these gases are rarely pure.
One of the most common impurities is carbon dioxide, which lowers energy efficiency and can damage pipelines through corrosion.
Removing CO₂ before the gas is used is therefore essential.
A research team at Chiba University in Japan has developed a promising new way to do this using graphene, a material made of a single layer of carbon atoms arranged in a honeycomb pattern.
Led by Associate Professor Tomonori Ohba, the scientists showed that adding oxygen atoms to ultrathin graphene membranes can dramatically improve their ability to separate carbon dioxide from methane.
Their results were published in the journal Carbon.
Graphene is an appealing material for gas filtration because it is extremely strong, stable and incredibly thin. In its natural form, graphene blocks all gases. But when tiny holes, known as nanopores, are added, gas molecules can pass through. The challenge is controlling these pores so that only certain gases get through.
The researchers found that pore size is critical. If the holes are too large, both methane and carbon dioxide flow through easily, making separation impossible. To understand this effect in detail, the team combined laboratory experiments with computer simulations. They tested how CO₂ and methane moved through graphene pores ranging from less than a quarter of a nanometer to nearly one nanometer in size.
The simulations revealed that graphene membranes allow gas to pass through very quickly, much faster than many traditional filters. However, meaningful separation only occurred when pore sizes were close to 0.4 nanometers. Larger pores showed little ability to distinguish between the two gases.
When the researchers compared simulations with real experiments, they noticed a mismatch. In practice, the membranes were less permeable than expected. The reason turned out to be oxygen. Real graphene membranes naturally contain oxygen atoms at their edges and defects, something the initial simulations did not fully account for.
Once oxygen functional groups were added to the computer models, the results changed dramatically. Carbon dioxide molecules interacted strongly with oxygen atoms, while methane did not. This allowed CO₂ to pass through more easily and improved separation, even when the pores were somewhat larger.
To confirm this effect, the team treated graphene membranes with oxygen plasma, deliberately adding oxygen to the material. The modified membranes showed much better performance, closely matching the updated simulations.
These findings suggest that carefully engineered graphene membranes could offer a powerful new way to purify natural gas and biogas. By removing carbon dioxide more efficiently and with less energy, this technology could help lower costs, reduce emissions and support cleaner energy systems in the future.
Source: KSR.
