The alarming rise in Earth’s temperatures due to global warming is projected to have devastating effects on all life on the planet. The main culprit: the rise in carbon dioxide (CO2), 36 billion tons of which were emitted in 2019 alone.
One way to mitigate or potentially even reverse the effects of climate change is to capture CO2 from the air. Unfortunately, while burning fossil fuels is easy, re-capturing CO2 released into the atmosphere is not. Despite the obvious increase in CO2 levels, the gas still makes up only a small fraction of the air. On top of this, CO2 is one of the most stable molecules in air, making it difficult to absorb chemically.
“While carbon capture technologies exist, they are costly and do not perform well at low concentrations of CO2,” said Sing Yang Chiam, Deputy Executive Director of A*STAR’s Institute of Materials Research & Engineering (IMRE). “Capturing CO2 directly under ambient conditions is even more difficult.”
In the present study, first author Mohammad Tanhaei, a graduate student working at IMRE, turned to defect engineering to develop a material that can efficiently capture CO2. Although defects are regarded as undesirable in most situations, intentionally added defects can improve a material’s properties and performance. However, defects are often introduced using post-processing techniques, which are hard to control and require additional time and cost.
Instead, the researchers directly introduced defects while forming a thin film of molybdenum (Mo) oxide, a material with multiple stable oxidative states that can interact with the highly stable CO2.
In doing so, the team boosted the material’s ability to capture CO2 to about 23 mmol/g under standard conditions, which, Chiam notes, is one of the best-reported performances to date. An additional benefit of using molybdenum oxide in a thin film format instead of a powder, as is usually the case for sorption applications, is that there will be lower toxicity and contamination risks, he added.
“We were pleasantly surprised that the material on a supporting substrate had superior sorption performance, which we attributed firstly to the lack of ‘dead mass’ that exists in powders and secondly to reactive meta-stable defects,” Chiam said.
The researchers expect that the material can be developed to capture CO2 in industrial settings or used as a coating on the walls of buildings and tunnels to remove CO2 indoors.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research & Engineering (IMRE).