Electron Transfer Dynamics in Semiconductor鈥揅hromophore鈥揚olyoxometalate Catalyst Photoanodes

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• 作者：Xu Xiang ; John Fielden ; William Rodr铆guez-C贸rdoba ; Zhuangqun Huang ; Naifei Zhang ; Zhen Luo ; Djamaladdin G. Musaev ; Tianquan Lian ; Craig L. Hill
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：January 17, 2013
• 年：2013
• 卷：117
• 期：2
• 页码：918-926
• 全文大小：394K
• 年卷期：v.117,no.2(January 17, 2013)
• ISSN：1932-7455

文摘

Triadic photoanodes have been prepared based on nanoporous films of the metal oxides ZrO₂, TiO₂, and SnO₂, sensitizer [Ru(bpy)₂(dpbpy)]²⁺ (P2), and polyoxometalate water oxidation catalyst [{Ru₄O₄(OH)₂(H₂O)₄}(纬-SiW₁₀O₃₆)₂]^{10鈥?/sup> (1) and investigated for their potential utility in water-splitting dye-sensitized photoelectrochemical cells. Transient visible and mid-IR absorption spectroscopic studies were carried out to investigate the charge separation dynamics of these systems, indicating that electron transfer from photoexcited P2 to TiO₂ and SnO₂ is still the main excited state quenching pathway in the presence of 1. Furthermore, the accelerated recovery of the P2 ground state bleach in the presence of 1 results from ultrafast (nanosecond) electron transfer from catalyst to oxidized dye. Catalyst loading appears to depend largely on the point of zero charge of the supporting oxide and as such is significantly lower on SnO₂ than on TiO₂: nonetheless, the rate of recovery of the ground state bleach is similar in both TiO₂-P2-1 and SnO₂-P2-1 films. Spectral evidence for the formation of long-lived charged separated states is provided by the observation of signals persisting beyond 0.5 渭s which are attributed to Stark effect induced change of the P2 spectrum and/or formation of oxidized 1. Photoelectrochemical measurements on TiO₂-P2 and TiO₂-P2-1 photoanodes under visible light irradiation indicate a ca. 100% photocurrent enhancement in the presence of 1, suggesting light-driven water oxidation by the TiO₂-P2-1 system with an internal quantum efficiency of ca. 0.2%. The fast formation and long lifetime of the photo-oxidized catalyst suggest that photoanodes of this type may reward further optimization through the introduction of faster catalysts and stabilization of the binding of the dye to the electrode.}