A Flourinated Ionic Liquid as a High-Performance Fuel Cell Electrolyte

Abstract

This is the first report of a fuel cell with a proton-conducting ionic liquid (pIL) electrolyte that outperforms one with aqueous concentrated (85%) phosphoric acid over all current densities. The new pIL, 2-fluoropyridinium triflate (2-FPTf), is a fluorinated pIL that was made by mixing equimolar amounts of 2-fluoropyridine and triflic acid. A Pt-catalyzed fuel cell fed dry hydrogen and oxygen gases was stable at 80°C with neat 2-FPTf as the electrolyte. The polarization curve showed more than 15% improvement in performance (> 0.1 V cell voltage gain) compared to an identical fuel cell except with aqueous 85% phosphoric acid as the electrolyte. The stability of the fuel cell with 2-FPTf is attributed to it being a fluorinated electrolyte that does not wet Teflon. The improved fuel cell performance is attributed to low water-activity of the electrolyte leading to suppression of oxide formation on Pt and improved cathode performance. This was supported by the voltammetry of Pt in 2-FPTf electrolyte equilibrated with oxygen, which showed oxygen reduction begins near the thermodynamic limit of 1.2 V versus RHE at 80°C.

Oxygen Reduction Reaction in Ionic Liquids: Fundamentals and Applications in Energy and Sensors

“…In another study, Thomson et al used 2-fluoropyridinium trifluoromethanesulfonate [FPy]­[TfO] as proton conducting electrolyte for a fuel cell. Under the same conditions, the performance of [FPy]­[TfO]-based fuel cell was found to be 15% better than that with 85% phosphoric acid electrolyte.…”

“…However, the fuel cell performance of the composite membrane made of a sulfonated polyimide and [empa][NfO] is slightly inferior to the composite membrane made of [dema][TfO]. The higher cell performance of [dema][TfO]-based composite membrane is attributed to the superior bulk properties of [dema][TfO].In another study, Thomson et al138 used 2-fluoropyridinium trifluoromethanesulfonate [FPy][TfO] as proton conducting electrolyte for a fuel cell. Under the same conditions, the performance of [FPy][TfO]-based fuel cell was found to be 15% better than that with 85% phosphoric acid electrolyte.…”

Physicochemical properties of phosphonium-based and ammonium-based protic ionic liquids

“…11 PILs prepared from oxoacids tend to exhibit low overpotentials for H 2 oxidation and O 2 reduction. 4,26,27 Among the oxoacids, triflic acid (CF 3 SO 3 H) is a superacid with a pK a of around À14. 28 Appleby and Baker 29 reported that the oxygen reduction reaction at a Pt surface in 1.1 mol L À1 CF 3 SO 3 H solution showed apparently greater kinetics than that in 85% H 3 PO 4 solution at 1 atm and ordinary temperature.…”

The Synthesis of Poly(Vinyl Alcohol) Grafted with Fluorinated Protic Ionic Liquids Containing Sulfo Functional Groups

“…Therefore, ProticILs have a great potential in proton exchange membranes elaboration for fuel cells application [ 26 , 27 ]. Fluorinated ionic liquids have attract special attention owing to the high oxidative stability enabling the suppression of oxide formation on Pt and improved cathode performance [ 28 ]. Thomson et al [ 28 ] reported the 2-fluoropyridinium triflate (2-FPTf), proton-conducting ionic liquid, as a more efficient electrolyte compared to the commonly used aqueous concentrated (85%) phosphoric acid.…”

“…Fluorinated ionic liquids have attract special attention owing to the high oxidative stability enabling the suppression of oxide formation on Pt and improved cathode performance [ 28 ]. Thomson et al [ 28 ] reported the 2-fluoropyridinium triflate (2-FPTf), proton-conducting ionic liquid, as a more efficient electrolyte compared to the commonly used aqueous concentrated (85%) phosphoric acid. However, the main drawback of the polymeric membrane materials possessing the ionic liquids is the gradual and uncontrollable leaching out of ionic liquid from the membrane structure during the exploitation [ 29 ].…”