Colloidal bimetallic PdRh nanoparticles (NPs) of controlled size and structure were synthesized and tested as catalysts models in aqueous phase hydrodechlorination (HDC) (303 K, 1 atm) using 4-chlorophenol (4-CP) as target compound. The colloidal bimetallic PdRh NPs were synthesized by chemical reduction, using methanol as reducing agent and poly(N-vinyl-2-pyrrolidone) (PVP) as capping agent. Two methods of synthesis (co-reduction, successive reduction) and three different Pd/Rh nominal molar ratios (0.2, 1, and 5) were used. The NPs were characterized by means of TEM, HAADF-STEM/EDS and XPS. High 4-CP conversion values (85-100%) were achieved at very low metal concentration (1.23 x 10(-3) g L-1). Phenol, cyclohexanone, cyclohexanol, and cyclohexene were the reaction by-products detected. Core-shell and cluster-in-cluster NPs structures were obtained by varying the method of synthesis and the Pd/Rh molar ratio. The activity was found to increase with the Pd/Rh ratio. Activity values up to 67.0 mmol g(-1) min(-1), which are significantly higher than those obtained in previous works with monometallic Pd (39.1 mmol g(-1) min(-1)) and Rh (29.4 mmol g(-1) min(-1)) under equivalent conditions, were achieved. Significant differences in activity and selectivity were found between the NPs with Pd/Rh ratios of 0.2-1 synthesized by co-reduction and successive reduction. The results indicate that the study of the performance of Pd/Rh bimetallic catalysts in HDC requires some consideration about the structure of the NPs, since the metal arrangement can determine an enhancement in the activity of the catalysts. (C) 2014 Elsevier B.V. All rights reserved.