Formic Acid Oxidation in a Polymer Electrolyte Fuel Cell: A Real‐Time Mass‐Spectrometry Study

The electro‐oxidation of formic acid was studied in a direct‐oxidation polymer‐electrolyte fuel cell at 170°C using real‐time mass spectrometry. The results are compared with those obtained for methanol oxidation under the same conditions. Formic acid was electrochemically more active than methanol on both Pt‐black and Pt/Ru catalysts. The polarization potential of formic acid oxidation was ca. 90 to 100 mV lower than that of methanol. The oxidation of formic acid was dependent on the water/formic acid mole ratio. The best anode performance was obtained using a water/formic acid mole ratio of ∼2. In addition, Pt/Ru catalyst was more active than Pt‐black for formic acid oxidation. The mass spectrometric results showed that is the only reaction product of formic acid oxidation. The results are discussed in terms of possible formic acid oxidation mechanisms.