Ru/polypyrrole/foam Ni composite electrodes were electrochemically deposited for application to electrocatalytic hydrodechlorination of pentachlorophenol (PCP) in aqueous solution. We characterized the Ru/polypyrrole/foam Ni composite electrode by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry. The polypyrroles were uniformly distributed on the nickel foam and Ru particles in the size range of 5-8 nm formed an amorphous layer on the polypyrrole/foam Ni composite surface. Compared with the crystalline electrodes of the Ru/foam Ni electrode, the Ru/polypyrrole/foam Ni composite electrodes showed better electrocatalytic dechlorination efficiency and greater stability. At a Ru loading of 0.06 mg/cm(2), cathode potential of -1.2 V, and H2SO4 concentration of 0.2 mol/L, the degradation efficiency of PCP reached 94.3% with a dechlorination efficiency of 88%. This performance was well maintained after 8 cycles of reuse. (C) 2018 Elsevier Ltd. All rights reserved.