Room temperature molten fluorohydrogenates for electrochemical systems

Abstract

Highly conductive room temperature molten salts (RTMSs), 1-ethyl-3-methylimidazolium fluorohydrogenates (EMIm(HF)nF) have been applied to electrolytes of an electrical double layer capacitors (EDLC) and a fuel cell (FCs). An EDLC using EMIm(HF)23F electrolyte and activated carbon electrodes in a non-metal cell exhibits a capacity of approximately 100 F g-1 -carbon at room temperature when the charge voltage is set at 2.2-2.4 V. A FC using EMIm(HF)23F electrolyte and platinum black electrodes exhibits a stable open circuit voltage of 1.1 V under the flow of hydrogen and oxygen gas of 1 atm at 298 K. The I-V behavior is comparable to that for the H2SO4 FC operating under the same condition. A new RTMS, N-ethyl-N-methylpyrrolidinium fluorohydrogenates (EMPyr(HF) 2,3F) exhibits ionic conductivity of 75 mS cm-1 and an electrochemical window of around 5 V.