Effects of Nafion ionomer content on the performance of membraneless direct formate fuel cells

Abstract

Herein, the performance of alkaline, membraneless, and direct formate fuel cells (DFFCs) in a particular configuration was measured and investigated at various fuel concentrations ranging from 1 to 5 M and fuel flow rates ranging from 1 to 5 mL/min, with anode Nafion ionomer contents of 3.73, 2.49, and 1.87 mg/cm2, at cell temperatures ranging from room temperature to 60℃. An anolyte solution containing potassium formate (HCOOK) and potassium hydroxide (KOH) was fed into the flow field sandwiched between the anode and cathode catalyst layers, while air was forced into the airflow field at a 100-sccm flow rate as the oxidant. Both Pd and Pt are used as the anode and cathode catalysts, respectively, of the DFFCs with 2-mg/cm2 identical loading. The results showed that both the open circuit voltage and the maximum power density of the DFFCs were enhanced by reducing the Nafion ionomer content. Besides, feeding the DFFCs with the anolyte containing 3-M HCOOK in 3-M KOH yielded the highest cell output. As the DFFCs were fed with the anolyte containing 3-M HCOOK in 3-M KOH at 3 mL/min with anode Nafion ionomer content of 1.87 mg/cm2, the peak power density values of the fuel cells at room temperature and 60℃ were 66.24 and 85.60 mW/cm2, respectively.