Abstract
This article describes the development of a high power density Direct Formate Fuel Cell (DFFC) fed with potassium formate (KCOOH). The membrane electrode assembly (MEA) contains no platinum metal. The cathode catalyst is FeCo/C combined with a commercial anion exchange membrane (AEM). To enhance the power output and energy efficiency we have employed a nanostructured Pd/C-CeO2 anode catalyst. The activity for the formate oxidation reaction (FOR) is enhanced when compared to a Pd/C catalyst with the same Pd loading. Fuel cell tests at 60 °C show a peak power density of almost 250 mW cm−2. The discharge energy (14 kJ), faradic efficiency (89%) and energy efficiency (46%) were determined for a single fuel charge (30 mL of 4 M KCOOH and 4 M KOH). Energy analysis demonstrates that removal of the expensive KOH electrolyte is essential for the future development of these devices. To compensate we apply for the first time a polymeric ionomer in the catalyst layer of the anode electrode. A homopolymer is synthesized by the radical polymerization of vinyl benzene chloride followed by amination with 1,4-diazabicyclo[2.2.2]octane (DABCO). The energy delivered, energy efficiency and fuel consumption efficiency of DFFCs fed with 4 M KCOOH are doubled with the use of the ionomer.
Highlights
Direct Formate Fuel Cells (DFFCs) are attractive power sources because as a fuel formate salts have specific advantages compared to alcohols like methanol and ethanol [1]
Industrial production involves fossil fuel derived precursors, formic acid can be obtained by renewable means such as the electrochemical reduction or catalytic hydrogenation of CO2 [3,4,5,6,7]
We have recently reported a study of the energy efficiency of Pt-free DFFCs (Pd/C anode, FeCo/C cathode and anion exchange membrane (AEM))
Summary
Direct Formate Fuel Cells (DFFCs) are attractive power sources because as a fuel formate salts have specific advantages compared to alcohols like methanol and ethanol [1]. Worldwide production of its precursor formic acid is around. Industrial production involves fossil fuel derived precursors, formic acid can be obtained by renewable means such as the electrochemical reduction or catalytic hydrogenation of CO2 (the energy or hydrogen used in such processes must be derived from renewable energy sources) [3,4,5,6,7]. DFFCs operate under alkaline conditions, which is advantageous as both the formate. Under basic conditions non-platinum catalysts can be used in the electrodes [8]. At high pH, the FOR does not pass through poisoning intermediates such as CO that can quickly passivate catalyst metal surfaces
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