World’s thinnest graphene filter and its use in carbon capture

One of the main culprits of global warming is the vast amount of carbon dioxide pumped out into the atmosphere mostly from burning fossil fuels and the production of steel and cement. In response, scientists have been trying out a process that can sequester waste carbon dioxide, transporting it into a storage site, and then depositing it at a place where it cannot enter the atmosphere. The problem is that capturing carbon from power plants and industrial emissions isn’t very cost-effective. The main reason is that waste carbon dioxide isn’t emitted pure, but is mixed with nitrogen and other gases, and extracting it from industrial emissions requires extra energy consumption—meaning a pricier bill.

Scientists have been trying to develop an energy-efficient carbon dioxide-filter. Referred to as a “membrane,” this technology can extract carbon dioxide out of the gas mix, which can then be either stored or converted into useful chemicals. However, the performance of current carbon dioxide filters has been limited by the fundamental properties of currently available materials.

Now, Professor Kumar Varoon Agrawal at École Polytechnique Fédérale de Lausanne in Switzerland led a team of chemical engineers to develop the world’s thinnest filter from graphene. But the graphene filter isn’t just the thinnest in the world, it can also separate carbon dioxide from a mix of gases such as those coming out of industrial emissions and do so with an efficiency and speed that surpasses most current filters. The work is now published in Science Advances.

The authors made carbon dioxide-sized holes in graphene, which allowed carbon dioxide to flow through while blocking other gases such as nitrogen, which are larger than carbon dioxide. The result is a record-high carbon dioxide-capture performance. For comparison, current filters are required to exceed 1000 gas permeation units (GPUs), while their carbon-capturing specificity, referred to as their “carbon dioxide/nitrogenseparation factor” must be above 20. The membranes that the EPFL scientists developed show more than ten-fold higher carbon dioxidepermeance at 11,800 GPUs, while their separation factor stands at 22.5.

In a nutshell, EPFL chemical engineers successfully developed a graphene filter for carbon capture that surpasses the efficiency of commercial capture technologies, and can reduce the cost carbon capture down to $30 per ton of carbon dioxide. The research team is now working on scaling up the process by developing a pilot plant demonstrator to capture 10 kg carbon dioxide per day, in a project funded by the Swiss government and Swiss industry.