Improvement of electrochemical reductive dechlorination of 2,4-dichlorophenoxyacetic acid using palladium catalysts prepared by a pulsed electrodeposition method

A nickel-foam, supporting palladium particles (PE-Pd/foam-Ni), was fabricated by pulsed electrodeposition. The PE-Pd/foam-Ni was proven to be a promising electrode for electro-catalytic reductive dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous solution. Compared to the traditional chemical deposition of palladium on a foam-nickel electrode, the PE-Pd/foam-Ni exhibits markedly improved removal efficiency and current efficiency (CE) for the dechlorination of 2,4-D. The PE-Pd/foam-Ni electrode with 0.67   mg Pd loading could achieve a maximum 2,4-D removal efficiency of 98% and a CE of 14% after 3   h at a current density of 1.5   mA   cm −2 . Moreover, the PE-Pd/foam-Ni maintained stable performance throughout three successive recyclability tests. As supported by physical-chemical characterization, the palladium catalysts originated from pulse electrodeposition possess a higher percentage of exposed {111} facets and a higher number of low-coordinated (edge/corner) sites, associated with a smaller particle size, in comparison with catalysts obtained from chemical deposition. Since the palladium atoms located on the edge/corner sites facilitate the catalytic reaction and the exposed {111} facets favor the generation and stabilization of chemisorbed active hydrogen, the enhanced electrocatalytic dechlorination performance of PE-Pd/foam-Ni electrode can be ascribed to the improved intrinsic properties of the Pd catalyst.