Triphenylphosphine Oxide-Derived Anolyte for Application in Nonaqueous Redox Flow Battery

Journal Article · 06 January 2025 · Journal of the American Chemical Society

DOI: https://doi.org/10.1021/jacs.4c07750 · OSTI ID:2497356

Mahoney, Emily R. ^[1]; Boudjelel, Maxime  ^[1]; Shavel, Henry ^[1]; Krzyaniak, Matthew D.  ^[2]; Wasielewski, Michael R.  ^[2]; Malapit, Christian A.  ^[2]

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1. Northwestern University, Evanston, IL (United States)
2. Northwestern University, Evanston, IL (United States); Paula M. Trienens Institute of Sustainability and Energy at Northwestern, Evanston, IL (United States)

Recent advances in redox flow batteries have made them a viable option for grid-scale energy storage, however they exhibit low energy density. One way to boost energy density is by increasing the cell potential using a nonaqueous system. Molecular engineering has proven to be an effective strategy to develop redox-active compounds with extreme potentials but these are usually challenged by resource sustainability of the newly developed redox materials. Here, we investigate the utility of phosphine oxides as anolytes with extremely negative potentials. Specifically, we found that cyclic triphenylphosphine oxide (CPO), has a highly negative potential (–2.4 V vs Fc/Fc⁺). Importantly, CPO is synthesized from triphenylphosphine oxide, a common industrial chemical waste with no commercial value. Structural and electrochemical characterization of the reduced radical anion showed that enhanced stability is due to cyclization or extended pi-conjugation. Importantly, mechanistic investigation into the decomposition of CPO under various solvents and electrochemical conditions allowed us to utilize an acetonitrile/DMF binary solvent system to enable a long-lived anolyte which exhibited no fade over 350 cycles. In conclusion, this work led to the development of a waste-derived cyclic phosphine oxide that exhibits excellent cycling stability making it an ideal anolyte toward the development of energy-dense RFBs.

• Research Organization: Northwestern University, Evanston, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: FG02-99ER14999
• OSTI ID: 2497356
• Journal Information: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 2 Vol. 147; ISSN 0002-7863
• Publisher: American Chemical Society (ACS)Copyright Statement
• Country of Publication: United States
• Language: English