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Carbon Nanotubes Can Outperform Other Carbon Capture Materials

Researchers discover how to tune the carbon-capture capacity of nanotubes

2 min read
Carbon Nanotubes Can Outperform Other Carbon Capture Materials
Snapshots of CO2 adsorption in double-walled carbon nanotube arrays (with an inner tube diameter of 2r=3 nanometers and various inter-tube distance at T=303 K and p=1 bar).
Illustration: Mahshid Rahimi & Deepu J. Babu

Whether you see carbon capture tools as solutions to environmental remediation or power generation, it has become increasingly clear that nanomaterials are pretty good at it.

Now researchers at Technische Universität Darmstadt in Germany and the Indian Institute of Technology Kanpur have found that they can tailor the gas adsorption properties of vertically aligned carbon nanotubes (VACNTs) by altering their thickness, height, and the distance between them.

“These parameters are fundamental for 'tuning' the hierarchical pore structure of the VACNTs,” explained Mahshid Rahimi and Deepu Babu, doctoral students at the Technische Universität Darmstadt who were the paper's lead authors, in a press release. “This hierarchy effect is a crucial factor for getting high-adsorption capacities as well as mass transport into the nanostructure. Surprisingly, from theory and by experiment, we found that the distance between nanotubes plays a much larger role in gas adsorption than the tube diameter does.”

Previously, carbon materials in gas adsorption-desorption suffered from hysteresis effects in which the property of the material was somewhat behind the factors that were changing it. In the case of carbon nanotubes, the sizes, structure, and distribution of the pores in the material were slow to react to these changes.

In research published in The Journal of Chemical Physics, the researchers first set out through computer modeling to gain a better theoretical understanding of adsorption and selectivity in carbon materials.

Then through experimentation, the researchers validated their models and demonstrated that VACNTs adsorbed the gases of carbon dioxide (CO2) and sulfur dioxide (SO2) better than traditional adsorption materials, such as porous carbon, zeolites, and metal organic frameworks within the mid-pressure (30 bars) regime. “This adsorption range is important for technologically relevant processes like gas storage for automotive purposes,” noted Rahimi in the release.

In future research, the plan is to introduce specific atoms to the carbon nanotubes for elemental doping.

Rahimi added: “This will allow us to further tune the gas selectivity. Another area we'll also explore is ‘controlled carbon nanotube openings’ in such VACNTs to increase the gas adsorption.”

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3D-Stacked CMOS Takes Moore’s Law to New Heights

When transistors can’t get any smaller, the only direction is up

10 min read
An image of stacked squares with yellow flat bars through them.
Emily Cooper

Perhaps the most far-reaching technological achievement over the last 50 years has been the steady march toward ever smaller transistors, fitting them more tightly together, and reducing their power consumption. And yet, ever since the two of us started our careers at Intel more than 20 years ago, we’ve been hearing the alarms that the descent into the infinitesimal was about to end. Yet year after year, brilliant new innovations continue to propel the semiconductor industry further.

Along this journey, we engineers had to change the transistor’s architecture as we continued to scale down area and power consumption while boosting performance. The “planar” transistor designs that took us through the last half of the 20th century gave way to 3D fin-shaped devices by the first half of the 2010s. Now, these too have an end date in sight, with a new gate-all-around (GAA) structure rolling into production soon. But we have to look even further ahead because our ability to scale down even this new transistor architecture, which we call RibbonFET, has its limits.

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