Performance improvement in direct formic acid fuel cells (DFAFCs) using metal catalyst prepared by dual mode spraying

In the present study, we investigate performance of direct formic acid fuel cells (DFAFCs) consisting of membrane electrode assembly (MEA) prepared by three different catalyst coating methods - direct painting, air spraying and dual mode spraying. For the DFAFC single cell tests, palladium (Pd) and platinum (Pt) are used as anode and cathode catalyst, respectively, and four different formic acid concentrations are provided as a fuel. In the measurements, dual mode spraying shows the best DFAFC performance. To overhaul how difference in coating method influences DFAFC performance, several characterization techniques are utilized. Zeta potential and TEM are used for evaluating anodic Pd particle distribution and its size. Cyclic voltammogram (CV) is measured to calculate electrochemical active surface (EAS) area in anode electrode of the DFAFCs, while charge transfer resistance (R_ct) is estimated by electrochemical impedance spectroscopy (EIS). As a result of the characterizations, Pd prepared by dual mode spraying induces the most uniform particle distribution and the smallest size, the highest EAS area and the lowest R_ct, which are matched with the DFAFC performance result. Conclusively, by adoption of the dual mode spraying, DFAFC can get the maximum power density as high as 240 mW cm^-2 at 5 M formic acid.