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 CH₂ Cl₂) on a Co-MoS₂ graphite felt cathode was investigated. The Co-MoS₂ electrocata-lyst 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 capac-itive 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 CH₂ Cl₂ (k₃ = 9.1 × 10⁻⁵ s⁻¹) < CHCl₃ (k₂ = 1.5 × 10⁻³ s⁻¹) < CCl₄ (k₁ = 2.8 × 10⁻³ s⁻¹).