A Noble-Metal-Free, Tetra-nickel Polyoxotungstate Catalyst for Efficient Photocatalytic Hydrogen Evolution

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• 作者：Hongjin Lv ; Weiwei Guo ; Kaifeng Wu ; Zheyuan Chen ; John Bacsa ; Djamaladdin G. Musaev ; Yurii V. Geletii ; Sarah M. Lauinger ; Tianquan Lian ; Craig L. Hill
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：October 8, 2014
• 年：2014
• 卷：136
• 期：40
• 页码：14015-14018
• 全文大小：288K
• ISSN：1520-5126

文摘

A tetra-nickel-containing polyoxotungstate, Na₆K₄[Ni₄(H₂O)₂(PW₉O₃₄)₂]路32H₂O (Na₆K₄-Ni₄P₂), has been synthesized in high yield and systematically characterized. The X-ray crystal structure confirms that a tetra-nickel cluster core [Ni₄O₁₄] is sandwiched by two trivacant, heptadentate [PW₉O₃₄]^{9鈥?/sup> POM ligands. When coupled with (4,4鈥?di-tert-butyl-2,2鈥?dipyridyl)-bis(2-phenylpyridine(1H))-iridium(III) hexafluorophosphate [Ir(ppy)₂(dtbbpy)][PF₆] as photosensitizer and triethanolamine (TEOA) as sacrificial electron donor, the noble-metal-free complex Ni₄P₂ works as an efficient and robust molecular catalyst for H₂ production upon visible light irradiation. Under minimally optimized conditions, Ni₄P₂ catalyzes H₂ production over 1 week and achieves a turnover number (TON) of as high as 6500 with almost no loss in activity. Mechanistic studies (emission quenching, time-resolved fluorescence decay, and transient absorption spectroscopy) confirm that, under visible light irradiation, the excited state [Ir(ppy)2(dtbbpy)]+* can be both oxidatively and reductively quenched by Ni₄P₂ and TEOA, respectively. Extensive stability studies (e.g., UV鈥搗is absorption, FT-IR, mercury-poison test, dynamic light scattering (DLS) and transmission electron microscopy (TEM)) provide very strong evidence that Ni₄P₂ catalyst remains homogeneous and intact under turnover conditions.}