Human emissions of greenhouse gases have become the primary drivers of global warming. In 2021, CO2 accounted for 79% of all man-made greenhouse gas emissions in the US. We need a massive transformation to actively remove carbon dioxide from the atmosphere or offset its effects to achieve net zero emissions.
Turning Threat Into Treasure
In collaboration with the US Department of Energy's Brookhaven National Laboratory, experts from Columbia University have designed a technology that would turn carbon dioxide from the atmosphere into carbon nanofibers. The paper discusses their approach, "CO2 fixation into carbon nanofibres using electrochemical-thermochemical tandem catalysis."
Absorbing CO2 or transforming it into other elements to reduce global warming is not new. However, this approach faces challenges as holding CO2 gas may result in leakage. Additionally, many CO2 transformations could result in immediately usable carbon-based compounds or fuels that quickly return CO2 to the environment.
According to chemical engineering professor Jingguang Chen, the novelty of this work is the attempt to convert CO2 into something that is not only value-added but also exists in a solid, useful form. These solid carbon materials have a lot of desirable qualities, like strength and electrical and thermal conductivity. Examples are carbon nanotubes and nanofibers, which measure billionths of meters in diameter.
However, removing carbon from carbon dioxide and assembling it into intricate structures is challenging. This is because over 1,000 degrees Celsius are needed for a single direct, heat-driven process.
To solve this problem, the researchers employed two distinct kinds of catalysis divided into different phases. For the first step, they use electrocatalysis, which involves electric current to accelerate chemical processes. When protons and electrons moved through water, CO2 was divided into CO and hydrogen gas.
In the second step, the iron-cobalt alloy thermocatalyst was activated using heat. It runs at temperatures near 400 degrees Celsius, colder than needed for a direct conversion of CO2. It was observed that adding a bit of metallic cobalt dramatically increases the creation of carbon nanofibers.
Researchers from the Center for Functional Nanomaterials (CFN) conducted transmission electron microscopy (TEM) analysis to investigate the specifics of these catalysts' workings. TEM revealed the crystal structures, morphologies, and elemental distributions within the carbon nanofibers, both with and without catalysts.
Environmentally-Friendly and Carbon Neutral
The new method boasts several advantages over conventional CO2 conversion techniques. First, this process operates at lower temperatures and ambient pressure, requiring significantly less energy. The two-step approach also ensures high efficiency, maximized CO2 utilization, and minimized waste.
Images from TEM show that as the carbon nanofibers grow, the catalyst gets pushed up and away from the surface, making it easier to recycle catalytic material. The process can be applied in large-scale nanofiber production, with sustainability improved by renewable energy. As a result, it can potentially achieve carbon-neutral or even carbon-negative results with new opportunities for CO2 mitigation.
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