Tunable Biomimetic Chalcogels with Fe4S4 Cores and [SnnS2n+2]4–(n = 1, 2, 4) Building Blocks for Solar Fuel Catalysis
2013
Shim, Yurina | Yuhas, Benjamin D. | Dyar, Scott M. | Smeigh, Amanda L. | Douvalis, Alexios P. | Wasielewski, Michael R. | Kanatzidis, Mercouri G.
Biology sustains itself by converting solar energy in a series of reactions between light harvesting components, electron transfer pathways, and redox-active centers. As an artificial system mimicking such solar energy conversion, porous chalcogenide aerogels (chalcogels) encompass the above components into a common architecture. We present here the ability to tune the redox properties of chalcogel frameworks containing biological Fe₄S₄ clusters. We have investigated the effects of [SnₙS₂ₙ₊₂]⁴– linking blocks ([SnS₄]⁴–, [Sn₂S₆]⁴–, [Sn₄S₁₀]⁴–) on the electrochemical and electrocatalytic properties of the chalcogels, as well as on the photophysical properties of incorporated light-harvesting dyes, tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺). The various thiostannate linking blocks do not alter significantly the chalcogel surface area (90–310 m²/g) or the local environment around the Fe₄S₄ clusters as indicated by ⁵⁷Fe Mössbauer spectroscopy. However, the varying charge density of the linking blocks greatly affects the reduction potential of the Fe₄S₄ cluster and the electronic interaction between the clusters. We find that when the Fe₄S₄ clusters are bridged with the adamantane [Sn₄S₁₀]⁴– linking blocks, the electrochemical reduction of CS₂ and the photochemical production of hydrogen are enhanced. The ability to tune the redox properties of biomimetic chalcogels presents a novel avenue to control the function of multifunctional chalcogels for a wide range of electrochemical or photochemical processes relevant to solar fuels.
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