Substantially Enhanced Power Output and Durability of Direct Formic Acid Fuel Cells at Elevated Temperatures

Development of direct formic acid fuel cell (DFAFC) is significantly constrained by low output performance and poor durability because of the sluggish formic acid oxidation reaction (FAOR) and the poisoning by CO ads intermediate on the Pt-based electrocatalyst at low operating temperatures. By operating DFAFCs at elevated temperatures, the peak power density (PPD) of the cell based on the Pt/C catalyst increases significantly. For example, the PPD of DFAFC reaches 198 mW cm −2 at 240 °C, eight times higher than that of the DFAFC at 70 °C. The study shows the surprising transition in power performance of DFAFCs at elevated temperatures. The increase of PPD for DFAFC against temperature is 121 mW cm −2 /100 °C at temperatures above 115 °C, almost three times higher than the 45 mW cm −2 /100 °C obtained at lower temperatures. The fundamental reason for the substantially enhanced power output and durability is the gradual transformation of the reaction kinetics from sluggish direct FAOR at low temperatures to fast H 2 oxidation reaction at elevated temperatures due to the increased in situ decomposition of formic acid on Pt/C catalysts at temperatures above 100 °C. This study demonstrates that operation at temperatures above 160 °C is most effective to promote performance and durability of DFAFCs.