Electrocatalytic Dechlorination of Chloroform in Aqueous Solution on Palladium/Titanium Electrode

Degradation Kinetics and Mechanism of Polychloromethanes Reduction at Co-MoS2/Graphite Felt Electrode

In this study, the electrochemical dechlorination of different polychloromethanes (CCl4, CHCl3, and CH2Cl2) on a Co-MoS2 graphite felt cathode was investigated. The Co-MoS2 electrocatalyst was prepared hydrothermally on a graphite felt support. The prepared catalyst’s characterization revealed the formation of hybridized CoSx and MoS2 nanosheets deposited on the pore structures of graphite. The influencing factor for the electro-dechlorination parameters such as applied current density, pH, and sample concentration on the dechlorination rate was optimized. A significant capacitive reduction current density peak of approximately 1 mA/cm2 was noted for CCl4 at a potential of −0.3 V (vs. AgCl). The dechlorination mechanism was attributed to the stepwise hydrogenolysis mechanism that involves the organochlorides bond cleavage by H* insertion. It was noted that the Co-MoS2 graphite felt electrode exhibited excellent catalytic activity toward the reduction of each of the chlorinated compounds with high selectivity toward the higher-order organochloride. Moreover, the dechlorination rates for each of the compounds were suited to the first-order kinetic model, and the estimated apparent rate constants showed the dechlorination in the following sequence CH2Cl2 (k3 = 9.1 × 10−5 s−1) < CHCl3 (k2 = 1.5 × 10−3 s−1) < CCl4 (k1 = 2.8 × 10−3 s−1).

Nucleophilic reactivity and electrocatalytic reduction of halogenated organic compounds by nickel o-phenylenedioxamidate complexes

Nickel(ii)-ate complexes supported by o-phenylenebis(N-methyloxamide) reacted with alkyl halides to form new imidate tautomers which were characterized by X-ray crystallography and FT-IR spectroscopy, and used for electroreduction of chloroform.

Electroreductive dechlorination of chlorophenols with Pd catalyst supported on solid electrode

Electroreductive dechlorination of chlorophenols with Pd catalyst supported on solidelectrode was studied. As solid electrodes, carbon cloth (CC), carbon felt (CF) and titanium mesh were used, and palladium was plated on solid electrodes by either electrolytic or electroless method. On each electrode with Pd, chlorophenols were qualitatively dechlorinated to phenol, while they were entirely intact on electrodes without Pd. Moreover, neither base electrode nor plating method significantly affected the activity of Pd as far as it was sufficiently loaded on the electrode. Based on the results in the experiments using one electrode repeatedly, Pd catalyst proved to possess a satisfactory duarability under the present condition. It was suggested that the reactive species responsinble for the dechlorination of chlorophenols could be formed during preliminary electrolysis. Thus, (Pd)x-H resulting from the adsorption of electrogenerated hydrogen on metallic Pd might be assumed most probable.

Electrocatalytic activity of Pd-loaded Ti/TiO2 nanotubes cathode for TCE reduction in groundwater

A novel cathode, Pd loaded Ti/TiO2 nanotubes (Pd-Ti/TiO2NTs), is synthesized for the electrocatalytic reduction of trichloroethylene (TCE) in groundwater. Pd nanoparticles are successfully loaded on TiO2 nanotubes which grow on Ti plate via anodization. Using Pd-Ti/TiO2NTs as the cathode in an undivided electrolytic cell, TCE is efficiently and quantitatively transformed to ethane. Under conditions of 100 mA and pH 7, the removal efficiency of TCE (21 mg/L) is up to 91% within 120 min, following pseudo-first-order kinetics with the rate constant of 0.019 min(-1). Reduction rates increase from 0.007 to 0.019 min(-1) with increasing the current from 20 to 100 mA, slightly decrease in the presence of 10 mM chloride or bicarbonate, and decline with increasing the concentrations of sulfite or sulfide. O2 generated at the anode slightly influences TCE reduction. At low currents, TCE is mainly reduced by direct electron transfer on the Pd-Ti/TiO2NT cathode. However, the contribution of Pd-catalytic hydrodechlorination, an indirect reduction mechanism, becomes significant with increasing the current. Compared with other common cathodes, i.e., Ti-based mixed metal oxides, graphite and Pd/Ti, Pd-Ti/TiO2NTs cathode shows superior performance for TCE reduction.