Ruthenium metallopolymer: Dawson polyoxomolybdate α-[Mo18O54(SO4)2]4- adduct films: sensitization for visible photoelectrocatalysis.
Thin films of the adduct formed from the electrostatic association of the metallopolymer, [Ru(bpy)(2)(PVP)(10)](2+), and the Dawson polyoxomolybdate α-[Mo(18)O(54)(SO(4))(2)](4-), POMo, have been formed on ITO electrodes using an alternate immersion approach. The Ru/POMo ratio is 4.5:1, which exceeds the 2:1 ratio expected on the basis of the charges of the Ru(2+) and POMo(4-) building blocks. This behavior arises because of the polymeric character of the cation. In the presence of a substrate that has an abstractable proton such as benzyl alcohol, these ruthenium-sensitized polyoxomolybdate films generate significant photocurrents under visible irradiation. Significantly, increasing the surface coverage of the adduct from 1.4 × 10(-10) to 8.1 × 10(-10) mol cm(-2) does not measurably increase the photocurrent observed. Scan-rate-dependent cyclic voltammetry reveals that the rate of homogeneous charge transport through the film is slow, which most likely results in only a fraction of the film thickness being active for photoelectrocatalysis. The photocurrent increases markedly when the driving force for the oxidation of POMo(5-), created by the photoelectrocatalytic oxidation of benzyl alcohol, is increased. This result is consistent with the dynamics of heterogeneous electron transfer being centrally important to the regeneration of the photoelectrocatalyst. A system in which the surface coverage and applied overpotential are optimized produces a photocurrent density of 190 ± 18 nA cm(-2) under 480 ± 5 nm irradiation.
School of Chemical Science, Dublin City University, Dublin, Ireland.
Jie
J
Zhu
James J
JJ
Walsh
Alan M
AM
Bond
Tia E
TE
Keyes
Robert J
RJ
Forster