In this study, stabilized Pd, Pt and Au nanoparticles were successfully prepared in aqueous phase using sodium carboxymethyl cellulose （CMC） as a capping agent. These metal nanoparticles were then tested for catalytic hydrodechlorination toward two classes of organochlorinated compounds （vinyl polychlorides includ- ing trichloroethylene （TCE）, tetrachloroethylene （PCE）, and alkyl polychlorides including 1,1,1-trichloroethane （1,1,1-TCA）, and 1,1,1,2-tetrachloroethane （1,1,1,2- TeCA）） to determine the rate-limiting steps and to explore the reaction mechanisms. The surface area normalized reaction rate constant, ksA, showed a systematic depen- dence on the electronic structure （the density of states at the Fermi level） of the metals, suggesting that adsorption of organochlorinated reactants on the metal catalyst surfaces is the rate-limiting step for catalytic hydrodechlorination. Hydrodechlorination rates of 1,1,1-TCA and 1,1,1,2-TeCA agreed with the bond strength of the first （weakest） dissociated C-C1 bond, suggesting that C-C1 bond cleavage, which is the first step for dissociative adsorption of the alkyl polychlorides, controlled the catalytic hydro- dechlorination rate. However, hydrodechlorination rates of TCE and PCE correlated with the adsorption energies of their molecular （non-dissociative） adsorption on the noble metals rather than with the first C-C1 bond strength, suggesting that molecular adsorption governs the reaction rate for hydrodechlorination of the vinyl polychlorides.
