In an effort to mitigate human-caused climate warming, scientists are focused on ways to remove carbon dioxide from the atmosphere. One of the more novel ways to do this has just been announced by scientists at the Brookhaven National Laboratory (BNL) and Columbia University (CU).
Carbon dioxide (CO2) is a potent greenhouse gas, which means that it has the ability to absorb heat and warm the planet. While it's a natural part of Earth's atmosphere, human activities have accelerated its release and in 2021, it was estimated that it accounted for 79% of all human-based greenhouse gas emissions. Therefore, scientists are trying to find ways to get it out of the atmosphere in the hope that it will help slow, or even reverse, the planet's dangerous warming trend.
Just last week, it was announced that scientists were able to remove CO2 from the air by implementing a fixation process in living bacteria. Last year, a CO2-absorbing concrete manufacturing process was announced, as was a manufactured wood that was able to grab the gas. And in 2022, it was revealed that the world's largest direct air capture plant for the removal of carbon dioxide was to be built in Wyoming.
Now, one of the more creative approaches to getting CO2 out of the air has been announced by researchers. It involves using both electrochemical and thermochemical reactions at relatively low heat to convert the harmful gas into beneficial carbon nanofibers.
While converting CO2 to nanofibers has been tried before, the process has required exceptionally high temperatures in excess of 1,000° C (about 1,832° F). The BNL and CU researchers got around this requirement by breaking the conversion process into multiple stages using different processes.
“If you decouple the reaction into several sub-reaction steps you can consider using different kinds of energy input and catalysts to make each part of the reaction work,” said study lead author Zhenhua Xie.
First, the researchers used an electrocatalyst of palladium supported on carbon, which split a mix of CO2 and water into carbon monoxide (CO) and hydrogen (H2) when an electrical current was introduced.
Then, they turned to a thermocatalyst made from an iron-cobalt alloy. This allowed them to spin the CO from the first stage into carbon nanofibers at a temperature of just 400° C (about 752° F) which, they say, is a much more achievable level of heat to use at industrial scales.
“By coupling electrocatalysis and thermocatalysis, we are using this tandem process to achieve things that cannot be achieved by either process alone,” said CU's Jingguang Chen, who led the research.
What's more, as the carbon nanofibers formed, they pushed the catalyst away from the surface, which allowed it to be captured and reused. In terms of reuse, the researchers also say that the hydrogen produced in the first stage could additionally be captured and reused as a fuel source.
“For practical applications, both are really important – the CO2 footprint analysis and the recyclability of the catalyst,” said Chen. “Our technical results and these other analyses show that this tandem strategy opens a door for decarbonizing CO2 into valuable solid carbon products while producing renewable H2.”
Because they are super strong, the researchers say the carbon nanofibers could have a range of applications, particularly as a strengthener for concrete.
“You can put the carbon nanofibers into cement to strengthen the cement,” said Chen. “That would lock the carbon away in concrete for at least 50 years, potentially longer. By then, the world should be shifted to primarily renewable energy sources that don’t emit carbon.”
The research has been published in the journal Nature Catalysis.
Source: Brookhaven National Laboratory
