Nanoscale zero valent iron (nZVI) particles, prepared by an in situ chemical reduction method, were employed for 2,4-dichlorophenoxyacetic acid (2,4-D) hydrodechlorination combined with the electro-chemical method using a palladium/nickel foam (Pd/Ni foam) electrode. The nZVI particles were characterized by X-ray diffraction and high-resolution transmission electron microscopy. Whereas the chemi-deposited catalytic electrode was further characterized using X-ray diffraction, scanning electron microscopy and Energy dispersive X-ray. More rapid hydrodechlorination rate was observed using synergistic technology and almost all of the 2,4-D were degraded in 4 h, which was 12.5% higher than that obtained in the independent electrochemistry system. Furthermore, the reaction mechanism was discussed in terms of the mutual effect between electrochemistry and nZVI. Both of the removal efficiency and the current efficiency depended on several factors including palladium loading, nZVI dosage and current density. Small amount of nZVI dosage not only effectively improved the efficiencies but also substantially reduced the processing cost. Palladium loading and current density had a greater effect on the efficiencies. Phenoxyacetic (PA), o-chlorophenoxyacetic acid (o-CPA) and p-chlorophenoxyacetic acid (p-CPA) have been identified as transformation products in reactive medium. (C) 2013 Elsevier B.V. All rights reserved.