Palladium (Pd) has been considered as an excellent option to replace platinum-based electrocatalysts in formic acid oxidation owing to its superb catalytic activity to Pt and cheaper material price. However, unstable catalytic activity of Pd is the most critical obstacle in the development of Pd-based electrocatalysts for formic acid oxidation, and the fundamental understanding on Pd deactivation is still incomplete. In this study, the activity of deactivated Pd in a formic acid oxidation was recovered to 93% by applying a cathodic bias potential of -0.2V vs. RHE. Based on in-situ electrochemical extended X-ray absorption fine structure spectroscopy analysis we show that cathodic polarization of Pd/C electrode could remove the adsorption of poisoning species by increasing bond length of Pd-Pd and further discuss on the origin of reactivation mechanism of Pd. (C) 2014 Elsevier Ltd. All rights reserved.