The accumulation of CO2 in the atmosphere is arguably humanity’s biggest challenge of the current century. Already, average global temperatures are nearly 1.5°C higher compared to the pre-industrial era. This is why transitioning to a society powered by 100% renewable energy should be a top priority for all stakeholders — but that might not be enough.
One of the reasons why CO2 accumulation is so menacing and tricky to solve is the fact that the greenhouse gas is notoriously difficult to reduce. This means that even by some miracle all fossil fuels were to disappear overnight, CO2 emitted yesterday can remain stable and warm the atmosphere for decades, perhaps centuries to come.
This vexing problem got Shaama Sharada, assistant professor at the University of Southern California, and colleague Kareesa Kron motivated to find a sustainable solution. In a first-of-its-kind computational study, the pair of researchers have found a chemical pathway that can convert CO2 into other molecules to produce useful materials, such as fuels and consumer products ranging from pharmaceuticals to even sustainable furniture.
The theoretical model that the researchers devised suggests that stimulating oligophenylene, an organic molecule, with ultraviolet (UV) light can turn it into a negatively charged anion. This would instantly shift electrons to the closest molecule, which can conveniently be CO2, making the greenhouse gas reactive and capable of being reduced and turned into different useful materials.
Typically, breaking down CO2 requires a lot of energy, which is just not economically feasible. However, the researchers believe UV rays from natural sunlight is enough to excite the catalyst molecule and kickstart the reduction of CO2.
“CO2 is notoriously hard to reduce, which is why it lives for decades in the atmosphere,” Sharada said. “But this negatively charged anion is capable of reducing even something as stable as CO2, which is why it’s promising and why we are studying it.”
“Most other ways to do this involve using metal-based chemicals, and those metals are rare earth metals,” said Sharada. “They can be expensive, they are hard to find and they can potentially be toxic.”
That being said, the method presented in the new paper is not without its own challenges and shortcomings. For instance, exciting the catalyst solely with sunlight can also be tricky, which is something that Sharada and colleagues are currently working on using quantum chemistry. Writing in The Journal of Physical Chemistry A, the authors claim systematic modifications to the oligophenylene catalyst meant to push electrons toward the center of the catalyst can speed up the reaction even further.
“One of those challenges is that, yes, they can harness radiation, but very little of it is in the visible region, where you can shine light on it in order for the reaction to occur,” said Sharada. “Typically, you need a UV lamp to make it happen.”