The electrocatalytic hydrogenolysis of pentachlorophenol (PCP) was carried
out under galvanostatic control, in an aqueous 1 M NaOH solution in which P
CP is fully soluble, and on particles of palladium or rhodium supported on
alumina (Pd(5%)/Al2O3 or Rh(5%)/Al2O3) and entrapped in a reticulated vitre
ous carbon (RVC) electrode. On Pd/Al2O3 and at 75 degrees C, the conversion
was complete (>99%) after 16 mol of electrons per mol of substrate (16 F m
ol(-1)) were consumed, and phenol was the sole product formed in 98% yield
(61% current efficiency). On Rh/Al2O3 and 25 degrees C, 100% conversion was
reached after 24 F mol(-1), and cyclohexanol was obtained in 98% yield wit
h some 2% of cyclohexanone (62% current efficiency). The ease of electrocat
alytic hyrogenolysis was found to increase in the following order: PCP < 2,
6-dichlorophenol < 4-chlorophenol.