Accumulation of Multiple Oxidative Equivalents at a Single Site by Cross-Surface Electron Transfer on TiO2

作者：Song Wenjing; Ito Akitaka; Binstead Robert A; Hanson Kenneth; Luo Hanlin; Brennaman M Kyle; Concepcion Javier J; Meyer Thomas J^*

来源：Journal of the American Chemical Society, 2013, 135(31): 11587-11594.

DOI：10.1021/ja4032538

The photodriven accumulation of two oxidative equivalents at a single site was investigated on TiO2 coloaded with a ruthenium polypyridyl chromophore [Ru(bpy)(2)((4,4'-(OH)(2) PO)(2)bpy)](2+) ((RuP2+)-P-II, bpy = 2,2'-bipyridine, ((OH)(2)PO)(2)-bpy = 2,2'-bipyridine-4,4'-diyldiphosphonic acid) and a water oxidation catalyst [Ru(Mebimpy) 4,4'-(OH)(2)PO-CH2)(2)bpy)(OH2)](2+) ((ROH22+)-O-II, Mebimpy = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine, (4,4'-(OH)(2)PO-CH2)(2)bpy) = 4,4'-bis-methlylenephosphonato-2,2'-bipyridine). Electron injection from the metal-to-ligand charge transfer (MLCT) excited state of -(RuP2+)-P-II (-RuIIP2+*) to give -(RuP3+)-P-III and TiO2(e(-)) was followed by rapid (<20 ns) nearest-neighbor -(RuOH22+)-O-II to -(RuP3+)-P-III electron transfer. On surfaces containing both -(RuP2+)-P-II and -(RUOH23+)-O-III (or -(RuOH2+)-O-III), -(RuOH22+)-O-II was formed by random migration of the injected electron inside the TiO2 nanoparticle and recombination with the preoxidized catalyst, followed by relatively slow (mu-ms) non-nearest neighbor cross-surface electron transfer from -RuIIOH22+ to -(RuP3+)-P-III. Steady state illumination of coloaded TiO2 photoanodes in a dye sensitized photoelectrosynthesis cell (DSPEC) configuration resulted in the buildup of -(RuP3+)-P-III, -(RuOH2+)-O-III, and -Ru-IV=O2+, with -Ru-IV=O2+ formation favored at high chromophore to catalyst ratios.

• 出版日期2013-8-7