NSF Award
2120452
Per- and polyfluorinated alkyl substances (PFAS) are a group of chemicals that have been widely used for decades. As additives in numerous consumer products, PFAS have many desirable properties, including exceptional chemical resistance. However, this property makes them very difficult to remove from water using current treatment processes. The chemical stability also makes PFAS persist in the environment, causing significant concerns for human and ecological health. One promising way to treat PFAS in water to benign end products is electrochemical oxidation. Scientists and engineers have been exploring various strategies to enhance performance, including employing nanotechnology enabled catalysts. However, expensive metals are often required in this approach, and selective destruction of PFAS in the water that contains various other organic compounds has been challenging. The proposed research addresses these drawbacks through the development of next-generation catalysts that can selectively bind with and destroy PFAS even when the water contains many other compounds. This goal will be pursued by manipulating palladium (Pd) and nickel (Ni) catalysts to be atomically dispersed, a process known as ‘single-atom catalysis’ (SAC). SAC is the theoretical limit of downsizing materials, and represents the state-of-science advancement beyond nanotechnology. The outcomes of this research project will include development of a laboratory-scale prototype SAC electrochemical reactor tested with PFAS contaminated water. Results will be disseminated through reports, scientific journals, conferences, and lectures. This project will train graduate and undergraduate students at two universities to perform interdisciplinary research under a highly collaborative environment. High school students will be recruited via summer research internship and outreach courses, increasing scientific literacy and developing the Nation’s STEM workforce. <br/><br/>The overarching objective of the proposed project is to develop an innovative electrocatalytic process that can oxidatively destroy PFAS in complex water matrices to benign end products. This project is one of the first studies to explore SAC – the theoretical limit of material downsizing – as the target electrocatalyst architecture to achieve highly selective and efficient anodic destruction of PFAS. The focus of this research is on Pd and Ni catalysts based on their proven performance for PFAS degradation at nano-scale. The SAC configuration has numerous advantages over existing catalysis technology. SAC allows tunable metal-ligand interactions and coordination environments that are essential for i) selective binding of the metal catalytic centers to functional groups of PFAS, and ii) direct electron transfer from PFAS to the anode. In addition, extremely low consumption of raw materials and low-cost synthesis procedures for SAC alleviate or possibly eliminate cost concerns when using noble metals like Pd. Finally, SACs are likely much more stable than metallic clusters, an important consideration for reactor implementation. The research is based on the underlying hypothesis that SAC architecture eliminates metal-metal interactions that are inherent in metallic, crystalline nanoclusters, resulting in PFAS degradation kinetics enhanced to the maximum extent possible. This hypothesis will be tested through characterization of the synthesized materials using state-of-the-science EXASF, XANES, HAADF-STEM, and in-situ FTIR techniques. Reaction products will be identified using advanced chemical analytical techniques to correlate material property and PFAS degradation pathways. The successful completion of this project will advance understanding of SAC synthesis, SAC-driven electrocatalysis, and establish new strategies for PFAS destruction. The collaborative team consisting of two research groups at two institutions with complimentary specialties will provide unique multidisciplinary, collaborative training opportunities to participating graduate and undergraduate students. Summer courses focusing on fluorine chemistry and electrochemistry will be developed for high school students and teachers. The project team is committed to recruiting underrepresented students for all outreach and training activities to diversify the Nation’s STEM workforce and promote an inclusive culture for research and learning.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
