Redox Properties of the Water Oxidation Catalyst (bpy)2(H2O)RuORu(H2O)2(4+) in Thin Polymeric Films. Electrocatalytic Oxidation of C1- to C12

摘要

Chemically modified electrodes containing the ruthenium and osmium oxo-bridged dimers (BPY)2(H2O)MIII2O4+ (bpy = 2,2'-bipyridine) have been prepared by cation exchange into films of partially hydrolyzed-p-chlorosulfonated polystyrene deposited onto glassy carbon electrodes. Both similarities and differences appear in comparing solution and film redox and acid-base properties: (1) As in solution the dimers undergo an initial one-electron oxidation, but the charge-transfer processes leading to higher oxidation states are inhibited in the polymeric film. (2) Reduction of the dimer are less acidic than in solution. The catalytic oxidation of chloride ion by electrodes containing the Ru dimer has been studied in detail. Oxidation of a 1.0 M LiC1 solution occurs with an initial current density of 100 mA sq.cm, and 26000 turnovers/Ru site are obtained before deactivation of the catalyst occurs. Rotated-disk experiments show that the oxidation of Chloride is independent of rotation rate but linearly dependent on C1-. Deactivation of catalyst appears to occur by oxidatively induced a nation, possibly involving binding of sulfonate sites on the polymer to the dimer.