A new technique can convert carbon dioxide back into carbon at room temperature

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If we plan to limit climate change to an increase of just 2 degrees Celsius, reducing emissions and carbon dioxide (CO2) levels isn’t going to be enough. 

A new process has been discovered that can convert fossil fuels into solid carbon, requiring only a small use of electricity. In recent years, researchers have discovered a number of compounds that accelerate chemical reactions, such as carbon monoxide and methane, which can convert CO 2 into solid carbon compounds.

One such catalyst, first described in Nature Chemistry 2017, consists of catalytically active palladium mixed with liquid gallium. To get it to work at just 600 degrees Celsius, they turned to a catalyst made of a metal alloy at room temperature.

Esrafilzadeh, Daneneke and their colleagues wanted to see if something similar would work with CO2, and so they wanted another catalyst.

First, they produced an alloy of gallium, indium and tin that is liquid at room temperature and conducts electricity. They sprayed it with a mixture of silver and cerium into a glass tube and placed the silver mixture in the glass tubes, while a splash of water supported the conversion of CO2 into carbon. When the wire was inserted into the liquid metal, parts of the liquid surface of the compound reacted with oxygen from the surrounding air, creating a thin layer of carbon dioxide, similar to carbon monoxide in coal. Most of it remained, however, protected by the liquid metals, so that it did not react with oxygen or air.

Next, the researchers piped pure CO2 into the glass tubes and sent a jolt through the wire. This caused the CO2 to diffuse into a liquid metal, where it was converted into solid carbon by the electricity of the ceramic metal, Esrafilzadeh and his colleagues report today in Nature Communications.

A major advantage of the new approach is that the cerium catalyst does not stick, according to the researchers. Instead, carbon forms small black flakes on the surface of the liquid metal, which then dissolve and move to the side or bottom of a tube to continue the catalytic reaction. The exact mechanism of this reaction is unclear, however, as the ceramic ultimately releases solid carbon and pure oxygen only as a by-product.

The paper was described as “novel and pretty nice” by the American Chemical Society, the US National Academy of Sciences and the National Institute of Standards and Technology.

The experiment, which Esrafilzadeh calls a “first step,” would first have to be copied on a larger scale. Daeneke said: “You can’t literally turn back time, but turning carbon dioxide back into coal and burying it in the ground is a bit like turning back our emissions clock.” 

The carbon produced can be used in a wide range of materials, including biofuels, solar panels, wind turbines and even solar cells. But the biggest benefit would be if the technology were developed to suck CO2 out of the air.

If this amount were converted into solid carbon, it would essentially regenerate the coal mountains that the miners are digging out of the ground. The gigatons of insulation make it seem terrifying, “he wrote in an email. According to the US Environmental Protection Agency, humans emit about 1.5 billion tons of CO2 annually, roughly equivalent to the world’s population.

 

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