Identification of Active Hydrogen Species on Palladium Nanoparticles for an Enhanced Electrocatalytic Hydrodechlorination of 2,4-Dichlorophenol in Water

Clarifying hydrogen evolution and identifying-the active hydrogen species are crucial to the understanding of the electrocatalytic hydrodechlorination (EHDC) mechanism. Here,.monodisperse palladium naimpartides (Pd NPs); are used as a model catalyst to demonstrate the potential-dependent evolutions of three hydrogen species, including adsorbed atomic hydrogen (H*ads), absorbed atomic hydrogen (H*abs), and molecular hydrogen (H-2) on Pd NPs, and then their effect-on-EHDC of 2,4-dichloropherrol Our reSultS shbw that H*ads,H*abs, and H-2 all emerge at -0.65 V (Vs AglAgcl) and have increased amounts at more negative potentials, except for H*ads that exhibits a reversed trend With the potential varying from -0.85 to-0.95 V. Overall, the concentrations of these three species evolve in an order of H*abs < < H-2 in the,potential range of -0.65 to 0:85-V,, H*acis < H*als < H-2 in -0.85 to -1.00 V, and H*ads' < H2 < H*'abs in-1.00 to 1.10 V. By correlating the evolution of each hydrogen species with 2,4-DCP EHDC kinetics and efficiency, we find that H*ads is the active species, H *abs is inert, while H-2 bubbles are detrimental to-the EHDC reaction. Accordingly, for an efficient EHDC reaction, a moderate potential is desired to yield sufficient H*ads and limit H2 negative, effect. Our work presents a systematic investigation,on the reaction mechanism of EHDC on Pd catatysts,,which should advance the application of EHDC technology in practical enviroimi:ental remediation. (GRAPHICS)