Finding the best dopant to detect carbon dioxide with graphene

Carbon dioxide gas sensors, which adsorb CO₂ molecules, have potential applications in addressing global warming. Graphene-based CO₂ gas sensors can be operated under ambient conditions and at room temperature, but they must be doped with other materials because the chemical inertness of pure graphene limits how much CO₂ it can adsorb. Yuan Cai and Xuan Luo searched for a suitable dopant for graphene-based CO₂ gas sensors.

Originally, the authors tried doping the graphene sheet with boron, nitrogen and aluminum, without success. After discovering success with a MN₄ doped graphene sheet, where M is scandium, titanium, vanadium, chromium, manganese, cobalt, nickel, copper and zinc, they performed first-principles calculations using density functional theory to characterize the CO₂ gas sensing performance of graphene doped with these nine structures.

The authors calculated the adsorption energy, band structure, density of states, and charge transfer for MN₄. They found that the TiN₄ doped 4×4 graphene sheet had the strongest adsorption capability and the highest charge transfer with CO₂ molecules, making it the most suitable dopant for graphene sheets used in a CO₂ gas sensor.

“The next step will be to develop TiN₄ doped graphene into actual gas sensors,” said author Yuan Cai. “Once CO₂ is detected in certain areas, the sensors will be able to alert administrators of that area so they can respond to CO₂ emissions and help slow global warming.”

In addition to detecting locations that emit large amounts of CO₂, these gas sensors could also be used to monitor fermentation, aerobic respiration, photosynthesis and other processes that consume or produce CO₂.

Source: “First-principles investigation of carbon dioxide adsorption on MN₄ doped graphene,” by Yuan Cai and Xuan Luo, AIP Advances (2020). The article can be accessed at https://doi.org/10.1063/5.0029724 .