Dechlorination of Chlorobenzene on Single Crystal Electrodes of Platinum and Silver

抄録

Structural effects on the rate of the dechlorination of chlorobenzene have been studied using the low index planes of platinum and silver in acetonitrile solution. Chlorobenzene is electrolyzed on platinum electrodes using naphthalene as a mediator at -2.94 V vs. Ag/Ag⁺. The main product is benzene. A reaction via a mediator does not depend on electrodes in general, because it is a homogeneous catalytic reaction. Surface structure, however, affects the partial current density of benzene (j_C6H6) on platinum electrodes: Pt(111)<Pt(110)∼Pt(100). On silver electrodes, j_C6H6 shows no structural effect in the electrolysis using naphthalene. Electrolysis without naphthalene gives the same structural effect as that with naphthalene on platinum electrodes, whereas no silver electrode reduces chlorobenzene at -2.94 V vs. Ag/Ag⁺ without naphthalene. Therefore, the anomalous structural effect on the electrolysis with naphthalene is attributed to the existence of a direct reduction of chlorobenzene on platinum electrodes. Silver electrodes reduce chlorobenzene to benzene at more negative potential -3.17 V vs. Ag/Ag⁺ without naphthalene. The value of j_C6H6 depends on the surface structure: Ag(110)∼Ag(111)<Ag(100). The flat (100) terrace has the highest activity for the dechlorination of chlorobenzene.