CV pres - Electrochemical and photophysical study of a...

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David Grauer January 15, 2008 Electrochemical and photophysical study of a hydrogen evolving, photoactive iridium complex and cobalt electron relay
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Introduction Much time, energy and resource has been invested recently in alternative fuel sources. Among these fuels, hydrogen has emerged as a top competitor. While hydrogen is abundant, it is most typically bound to oxygen in water Objective is to efficiently reduce hydrogen, releasing it in its gaseous form, H 2 Many ways of accomplishing this reduction (e.g. electrolysis). This study focuses on a photocatalytic cycle using iridium and cobalt. Purpose is two fold: Discern electron transfer mechanisms and assess efficiency of three different Co electron relays (ER)
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Involved Complexes 1. [Co(bppy) 3 ] 2+ 2. [Co(dtb-bpy) 3 ] 2+ 3. [Co(trpy) 2 ] 2+ Electron Relays (ERs)
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General Mechanism H + ER - PS h PS * SR H ER PS - SR + SR H + ER - PS + SR + PS H ER PS * h Reductive Quenching Oxidative Quenching SR = Sacrificial Reductant
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Materials and Methods It was necessary to synthesize the three Co ERs and Ir complexes using tried and true techniques (Goldsmith et al., 2004). Sought to glean information about mechanism involved with function of ERs 1 and 2. ER 3 cannot produce H 2 and was used as a control. ERs went through three different studies to determine effectiveness and possible mechanisms and intermediates. Electrochemical (Cyclic Voltammetry), Photophysical (Quenching) and Photoreaction (Hyrdogen Production)
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Methods Continued Cyclic Voltammetry Performed only on the separate ERs (1,2 and 3). Voltammograms taken at scan rates between 30 and 30,000 mV/s. Results processed using Nicholson Shain analysis. Quenching Studies Measured lifetimes of the various ERs in the presence of the PS. Determine whether reductive or oxidative quenching dominates using Stern - Volmer analysis to quantify the various quenching constants. Hydrogen Production
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CV pres - Electrochemical and photophysical study of a...

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