Researchers at École Polytechnique Fédérale de Lausanne (EPFL) have developed advanced atom-thin graphene membranes with pyridinic-nitrogen at pore edges, showing unprecedented performance in CO2 capture. This research represents a major step toward more efficient carbon capture technologies. The study was published in the journal Nature Energy.
A schematic of porous graphene hosting pyridinic N (shown as purple spheres) at the pore edges. The resulting membrane is highly selective to CO2. Image Credit:Kuang-Jung Hsu (EPFL)
The global fight against climate change has made it more important than ever to develop effective and affordable carbon capture technologies. As such, researchers are looking into various novel approaches to significantly cut industrial carbon emissions.
Among these efforts, carbon capture, utilization, and storage (CCUS) has emerged as an essential technology that lowers carbon dioxide (CO2) emissions from industrial sources that are difficult to mitigate, like waste incinerators, power plants, cement factories, and steel mills. However, the energy-intensive processes used in the current capture methods make them expensive and unsustainable.
The current focus of research is to create membranes that can efficiently and selectively capture CO2, which will lower the energy and financial costs related to CCS. However, the selectivity and CO2 permeance of even cutting-edge membranes, like polymer thin films, are constrained, which reduces their scalability.
Therefore, the challenge is to develop membranes that can provide high selectivity and CO2 permeance at the same time, which is essential for efficient carbon capture.
Scientists at EPFL, under the direction of Kumar Varoon Agrawal, have now achieved a significant advancement in this field by creating membranes that exhibit remarkable CO2 capture capabilities through the addition of pyridinic nitrogen to the graphene pores' edges. The membranes exhibit great promise for a range of industrial applications due to their exceptional balance of high CO2 permeance and selectivity.
The first step for the researchers was to create single-layer graphene films on copper foil by chemical vapor deposition. By carefully oxidizing graphene with ozone to create oxygen-atom functionalized pores, the researchers were able to introduce pores into the material. The researchers then discovered how to react room-temperature ammonia with oxidized graphene to add nitrogen atoms at the pore edge in the form of pyridinic N.
Using a variety of methods, including scanning tunneling microscopy and X-ray photoelectron spectroscopy, the researchers verified the effective incorporation of pyridinic nitrogen and the creation of CO2 complexes at the pore edges. The binding of CO2 on graphene pores was significantly enhanced by the addition of pyridinic N.
The resultant membranes had an average CO2/N2 separation factor of 53 for a gas stream containing 20 % CO2, which was high for CO2/N2 separation factors. Surprisingly, streams containing less than 1 % CO2 had separation factors above 1000 due to the pyridinic nitrogen-mediated competitive and reversible binding of CO2 at the pore edges.
Additionally, the scientists demonstrated the scalability of the membrane preparation procedure by creating high-performing membranes at the centimeter scale. This is essential for real-world uses, allowing the membranes to be used in extensive industrial environments.
The high performance of graphene membranes in capturing CO2, even from dilute gas streams, can significantly lower the costs and energy requirements of carbon capture processes. This breakthrough could lead to more affordable and environmentally friendly CCUS solutions by creating new opportunities in the field of membrane science.
The uniform and scalable chemistry used in creating the membranes allows for imminent scale-up. The team is now aiming to produce these membranes through a continuous roll-to-roll process. The versatility and efficiency of these membranes have the potential to revolutionize industrial emission management and significantly contribute to a cleaner environment.
EPFL, GAZNAT, Swiss National Science Foundation, European Research Council, EPFL-Taiwan Ph.D. Scholarship program provided funding for the study.
Journal Reference:
Züttel, A., et al. (2024) Graphene membranes with pyridinic nitrogen at pore edges for high-performance CO2 capture. Nature Energy. doi.org/10.1038/s41560-024-01556-0