Electrochemical CO2 reduction to formic acid on a Pd-based formic acid oxidation catalyst

The electrochemical reduction of CO2 is a reaction of much current interest as a possible reaction for energy storage. In this paper, we show that on electrodeposited palladium on platinum, a good formic acid oxidation catalyst, the onset potential for CO2 reduction to formic acid is dramatically reduced in comparison to bulk palladium. Two different reaction pathways are observed; a pathway at low overpotential in which formic acid is produced from either direct bicarbonate reduction or from the reduction of CO2 generated from bicarbonate near the surface, and a pathway at more negative potentials where formic acid is produced from direct CO2 reduction. Furthermore, we show that reversible formic acid oxidation and CO2 reduction is possible on this catalyst, although unfortunately the processes are hindered by poisoning of the catalyst, most likely by CO.