Photoelectrochemical kinetics of eosin y-sensitized zinc oxide films investigated by scanning electrochemical microscopy.
Eosin Y is used as a sensitizer for nanoporous zinc oxide films for prospective applications in photoelectrochemical solar cells. The kinetics of the reduction of the intermittently formed photo-oxidized dye molecules by iodide ions in the electrolyte phase was investigated by using the feedback mode of scanning electrochemical microscopy (SECM). The bulk solution phase contained triiodide as electron transfer mediator, from which the ultramicroelectrode-generated iodide ions acted as electron donors for photo-oxidized Eosin Y molecules (D(+) (ads)) at the zinc oxide sample. Effective rate constants for the dye regeneration could be extracted from the SECM approach curves. The effective rate constants at different triiodide concentrations could be related to the rate constant for the reaction of the dissolved donor with photo-oxidized Eosin Y bound to ZnO, as well as to the overall rate of the photosensitization process. For the reaction D(+) (ads) + 1.5 I(-)-->D(ads) + 0.5 I(3) (-) a rate constant of k(ox) = (1.4+/-0.8)x10(8) cm(9/2) mol(-3/2) s(-1) was determined.
Shen
Yan
Y
Institut für Reine und Angewandte Chemie und Institut für Chemie und Biologie des Meeres, Fakultät für Mathematik und Naturwissenschaften, Carl-von-Ossietzky University Oldenburg, 26111 Oldenburg, Germany.
Nonomura
Kazuteru
K
Schlettwein
Derck
D
Zhao
Chuan
C
Wittstock
Gunther
G