Transforming Carbon Dioxide into Industrial Fuels

Transforming Carbon Dioxide into Industrial Fuels

Catalytic Reduction of Carbon Dioxide can help us control the Greenhouse Effect.

Greenhouse gases, like Carbon Dioxide, are the most dominant contributor to environmental pollution. These gases are spewed into our atmosphere on a regular basis from heavy industry, motor vehicles, and power plants. Considering the harmful effects of these gases, a lot of efforts are being made at a global level to limit these emissions. However, Haotian Wang, a Fellow at the Rowland Institute of Harvard, has gone for a different way of dealing with this problem. He, alongside his colleagues, has developed an improved system that uses renewable electricity to reduce Carbon Dioxide into Carbon Monoxide, which is used in several industrial processes. He explained the principal idea of his project by saying,

The most promising idea may be to connect these devices with coal-fired power plants or other industry that produces a lot of CO2. About 20 percent of those gases are CO2, so if you can pump them into this cell…and combine it with clean electricity, then we can potentially produce useful chemicals out of these wastes in a sustainable way, and even close part of that CO2 cycle.”

The same researching team published a similar paper in 2017 but that had two major limitations, scalability and cost. Wang mentioned that the system developed from the initial approach was hardly the size of a cell phone and used two electrolyte-filled chambers. Contrary to that, this new system needs a single 10-by-10 cm cell to produce nearly 4 liters of Carbon Monoxide per hour. In order to make it commercially viable, the researchers turned to Carbon Black, which is thousands of times cheaper than Graphene. Wang elaborated the difficulties they faced with the earlier model in the following words:

In that earlier work, we had discovered the single nickel-atom catalysts which are very selective for reducing CO2 to CO but one of the challenges we faced was that the materials were expensive to synthesize. The support we were using to anchor single nickel atoms was based on graphene, which made it very difficult to scale up if you wanted to produce it at gram or even kilogram scale for practical use in the future.”

Researchers are using a process similar to electrostatic attraction to absorb positively-charged nickel atoms into negatively-charged defects in carbon black nanoparticles. Not only is this economical but it is also highly selective for Carbon Dioxide reduction. Wang announced that the best they can produce with this latest technique is grams. Previously, they were only able to make milligrams in a batch. Having said that, the production of this catalyst can be increased to any scale but they are limited by the synthesis equipment they have.

The second challenge that the researching team had to overcome was linked with the working conditions of the system. The one proposed in 2017 used an electrode in one chamber to split water molecules into protons and Oxygen. The protons traveled through the liquid solution into the second chamber while the gas escaped from the first. Nickel catalyst would then help these protons to bind with the Carbon Dioxide molecules and break them into water and Carbon Monoxide.

The problem with this method was that only a trace amount of Carbon Dioxide was present around the catalyst as water was pretty much dominant in the chamber. An obvious solution to the problem was to increase the voltage, applied to the system, but that might split the water molecules into Hydrogen and Oxygen. Therefore, the team of Wang needed to figure out something else and they did exactly that. The method they adopted turned out to be a relatively simple one as they took the catalyst out of the solution. Wang referred to that and said,

We replaced that liquid water with water vapor, and feed in high-concentration CO2 gas. So if the old system was more than 99 percent water and less than 1 percent CO2, now we can completely reverse that, and pump 97 percent CO2 gas and only 3 percent water vapor into this system. Before those liquid water also functions as ion conductors in the system, and now we use ion exchange membranes instead to help ions move around without liquid water. The impact is that we can deliver an order of magnitude higher current density. Previously, we were operating at about ten milliamps-per-centimeter squared, but today we can easily ramp up to 100 milliamps.”

Despite all these findings, Wang acknowledged that the system still needs improvement, particularly in terms of stability, as we move forward with it. He expressed hope that ultimately the day will come when the industry will be able to capture the Carbon Dioxide and transform it into useful products.

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