Operation of the Alkaline Direct Formate Fuel Cell in the Absence of Added Hydroxide

Abstract

AbstractThe direct formate fuel cell (DFFC) has recently been demonstrated as a viable alkaline direct liquid fuel cell (DLFC) that does not require addition of hydroxide to the fuel stream for operation. In this work, we report that the DFFC can produce significant power at low temperatures without added hydroxide, especially when compared with other alkaline DLFCs powered by alcohols. Using oxygen at the cathode, the DFFC powered by 1 M HCOOK achieves a maximum power density of 106 mW cm–2 at 50 °C and 64 mW cm–2 at 23 °C. Using air at the cathode, the same DFFC achieves a maximum power density of 76 mW cm–2 at 50 °C and 27 mW cm–2 at 23 °C. These power densities were achieved without addition of hydroxide to the fuel stream. Constant current operation demonstrates that the maximum power density can be maintained at least for several hours of operation. Finally, we use electrochemical analysis to demonstrate that the formate oxidation reaction is not dependent on pH between 9 and 14, which permits the use of formate fuel without added hydroxide in the DFFC. An alkaline DLFC that does not require added hydroxide is promising for safe and practical operation.