Nobel Metal Modified Foam Electrode For Electrochemical Dehalogenation Of Organic Halogen Compounds

The catalytic activity and stability of electrodes are influenced by the composition of the electrodes. This paper focused on the preparation of silver-modified copper foam electrode (Ag/Cu foam electrode) and palladium-modified nickel electrode with an interlayer of silver (Pd/Ag/Ni foam electrode). Explore the activity of Ag/Cu foam electrode with respect to the debromination of mono-bromoacetic acid (MBAA). And the dechlorination activity of Pd/Ag/Ni foam electrode was evaluated by monitoring the dechlorination of2-Chlorobiphenyl (2-CB).To improve the effectiveness of debromination of organic bromine compounds, a series of Ag/Cu foam electrode was prepared via chemical deposition, using AgNO3as the precursor. The crystal structure and morphology of the electrodes were measured by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that zero-valence Ag particles dispersed finely on the Cu foam surface and their number increased with Ag loading. Electrocatalytic activity was evaluated by monitoring the debromination of MBAA. Ion chromatography (IC) analysis verified that acetic acid and bromine ion (Br-) were the main debromination products of MBAA. The Ag/Cu foam electrode exhibited higher debromination activity than Cu foam. The results showed that as the Ag loading increased, the removal of MBAA and the current efficiency (CE) increased. But after getting a level, any further increase in Ag loading would have only slight positive effects on the debromination of MBAA and current efficiency. With the current density increased, the removal of MBAA increased but the CE reduced. Higher or lower pH inhibited electrocatalytic activity. The variation of the current efficiency found the same trend. Synthesizing these findings, the best operational conditions were a silver loading of2.0mg/cm, applied current density of5.5mA/cm2, and pH7.0. After five successive cycles, the Ag/Cu electrode remained stable for the electrocatalytic debromination of MBAA. We suggest that the improved electrocatalytic activity of the Ag/Cu electrode is mainly attributable to a strong interaction between MBAA and the Ag particles on the surface of electrode.In order to enhance the activity and stability of the chemi-deposited palladium/nickel foam (Pd/Ni foam) electrode used in the electrochemical dechlorination process, the electrochemical deposition of silver or copper onto a nickel foam substrate (Ag/Ni foam or Cu/Ni foam) was applied before the chemical deposition of palladium. The physicochemical properties of the resultant material (Pd/Ag/Ni foam and Pd/Cu/Ni foam) were characterized by XRD and SEM. The results showed that the interlayer not only provides extremely larger specific surface than Pd/Ni foam electrode, but also makes Pd particles can deposit firmly on the surface.2-CB was selected as an indicator in dechlorination experiments to evaluate the effect of the interlayer. Quantitative analysis by high-performance liquid chromatography (HPLC) found that the main final product of2-CB dechlorination is biphenyl. Compared to the Pd/Ni foam electrode, Pd/Ag/Ni foam electrode and Pd/Cu/Ni foam electrode consistently had relatively higher electrocatalytic activity and current efficiency (CE). And the result indicated that Pd/Ag/Ni foam electrode exhibited better dechlorination activity than Pd/Cu/Ni foam electrode. Those demonstrated the enhancement of electrochemical dechlorination by the presence of silver interlayer. The effects of Ag loading, Pd loading and current density were investigated by using those Pd/Ag/Ni foam electrodes. The best dechlorination activity was obtained at an Ag loading of6.0mg/cm2, a Pd loading of1.78mg/cm2, and current density of5.0mA/cm2.