Closing the greenhouse gap: turning harmful gas into useful fuel
In order to simultaneously combat the effect of carbon dioxide on the atmosphere and extend the search for a new source of fuel, a number of Harvard fellows discovered a method to transform carbon dioxide — the harmful gas behind much of global warming — into carbon monoxide a compound that can be used in industrial processes.
Haotian Wang, a fellow at the Rowland Institute at Harvard, spearheaded the research that made it possible to transform carbon dioxide into this usable fuel, which was published on Nov. 8 in a relatively new journal called Joule, a title under Cell Press. The idea, as Wang suggests, is to “connect these devices with coal-fired power plants or other industry that produces a lot of CO2 ... and combine it with clean electricity, [so that] we can potentially produce useful chemicals out of these wastes in a sustainable way, and even close part of that CO2 cycle.”
Wang had previously published the forefather of this idea in a 2017 paper in Chem, another title under Cell Press. The original idea involved using nickel atoms and a model similar to graphene, which would enter a chamber filled with water and carbon dioxide. The mixture of the nickel atoms and the model in a water solution allowed for the release of one of the oxygens atoms of the carbon dioxide, CO2, resulting in the production of carbon monoxide, CO, and oxygen.
There were two major issues that this method ran into that the newer one took into consideration and aimed to resolve.
The first was the use of the graphene-like model. Though this was fine to use chemically and served its purpose artfully at the atomic level, it proved to be extremely cost-ineffective. The answer that Wang and his team found in response to the extravagant cost of the graphene was the commercial product carbon black, which is thousands of times cheaper, according The Harvard Gazette, and serves the same function in this setting as something that can react with nickel atoms to produce a reduction agent to reduce the carbon dioxide in the water.
As an added bonus, the product of the reaction between the nickel atoms and the carbon black is highly selective for carbon dioxide reduction, meaning that it would be easier in the new method for the reduction of the carbon dioxide into carbon monoxide and oxygen to actually occur.
The second issue was a slightly larger issue to combat. The initial method involved the use of very little carbon dioxide dissolved in a lot of water, resulting in 1 percent of the solution being carbon dioxide that can be converted into carbon monoxide for fuel and 99 percent water.
The new solution the team found was to use water vapor instead of water itself.
Using water in the gaseous form instead of the liquid form allowed for the initial concentration of the mixture before the catalyst is introduced to be up to 97 percent carbon dioxide and only 3 percent water vapor.
With these two new changes in place, the system can not only produce more carbon monoxide to use as fuel but can also do it for extraordinarily cheap as compared to the proposed idea from previous research. There are still obstacles to overcome before they can start to use it enough to make an environmental and economic impact, Wang said. Wang specified that “it needs to have a continuous operation of thousands of hours ... but right now, we can do this for tens of hours, so there’s still a big gap.”
Ultimately, Wang maintains hope as to the direction that the research concerning converting carbon dioxide into usable fuel is going in. Eventually, he said, “the day may come when industry will be able to capture the CO2 that is now released into the atmosphere and transform it into useful products.” He’s also trying along with his group in order to produce copper-based catalysts in order to reduce carbon dioxide into more valuable products.