Tuning dehydrogenation behavior of formic acid on boosting cell performance of formic acid fuel cell at elevated temperatures

In high-temperature formic acid fuel cell (HT-FAFC), the dehydrogenation behavior of formic acid plays a significant role in boosting cell output performance by leading to a favorable and powerful hydrogen oxidation reaction (HOR) on the anode side instead of the direct formic acid oxidation reaction (dFAOR). The formic acid dehydrogenation mechanism of HT-FAFC at 200 °C is investigated by regulating concentration and flow rate. As a competitive path of dehydrogenation, unfavorable dehydration occurs simultaneously accompany by carbon monoxide (CO) release. It is found that high formic acid concentration is conducive to the dehydrogenation to produce more hydrogen, however, the reduction of water vapor content may promote the dehydration reaction and result in the inhibition of dehydrogenation. As the non-preferable alternative, the dehydration-caused total CO release remains under CO maximum tolerance (3%) of Pt catalyst at 200 °C which is unlikely to affect the power output of HT-FAFC. The permeation of formic acid can be considered as a barrier when the high concentration exceeds 12 mol L−1 or the flow rate exceeds 1 mL min−1. These findings may deepen understanding of formic acid consuming behavior of HT-FAFC anode, which helps to formulate strategies to improve cell performance in general. •Dehydrogenation behaviors of formic acid under HT-DFAFC at 200 °C have been studied.•The dehydrogenation pathways are determined by the ratio of formic acid to water.•Performance of DFAFC at 200 °C is controlled by hydrogen consumption for HOR.•The optimal performance of the HT-FAFC we may achieve is 203 mW cm−2 under 200 °C.