An illustration of the graphene carbon dioxide filter. Image: KV Agrawal, EPFL.
An illustration of the graphene carbon dioxide filter. Image: KV Agrawal, EPFL.

One of the prime contributors to global warming is the vast amount of carbon dioxide being pumped into the atmosphere, mostly from burning fossil fuels and producing steel and cement. In response, scientists have been trying to develop processes for sequestering waste carbon dioxide, transporting it to a storage site and then depositing it in a place where it cannot escape into the atmosphere.

The problem is that capturing carbon dioxide from power plants and industrial emissions isn't very cost-effective. Primarily, this is because waste carbon dioxide isn't emitted as a pure gas, but mixed with nitrogen and other gases, which means extracting it from industrial emissions requires extra energy and thus greater expense.

This has led scientists to try to develop an energy-efficient carbon dioxide filter, by using a membrane to extract carbon dioxide out of the gas mix, for subsequent storage or conversion into useful chemicals. "However, the performance of current carbon dioxide filters has been limited by the fundamental properties of currently available materials," explains Kumar Varoon Agrawal from the School of Basic Sciences at the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland.

In a paper in Science Advances, Agrawal and his team of chemical engineers now report developing the world's thinnest carbon dioxide filter from graphene, the world-famous 'wonder material' that won its discoverers the Nobel Prize for Physics in 2010. But this graphene filter isn't just the thinnest in the world, it can also separate carbon dioxide from a mixture of gases, such as those making up industrial emissions, and can do so with an efficiency and speed that surpasses most current filters.

"Our approach was simple," says Agrawal. "We 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 was 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/nitrogen separation factor', must be above 20. The membranes that the EPFL scientists developed show a more than 10-fold greater carbon dioxide permeance, at 11,800 GPUs, while their separation factor stands at 22.5.

"We estimate that this technology will drop the cost of carbon capture close to $30 per ton of carbon dioxide, in contrast to commercial processes where the cost is two-to-four times higher," says Agrawal. His team is now working on scaling up the process by developing a pilot plant demonstrator to capture 10kg of carbon dioxide per day, in a project funded by the Swiss government and Swiss industry.

This story is adapted from material from EPFL, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.