Standard Reduction Potentials for Oxygen and Carbon Dioxide Couples in Acetonitrile and N,N-Dimethylformamide

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• 作者：Michael L. Pegis ; John A. S. Roberts ; Derek J. Wasylenko ; Elizabeth A. Mader ; Aaron M. Appel ; James M. Mayer
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：December 21, 2015
• 年：2015
• 卷：54
• 期：24
• 页码：11883-11888
• 全文大小：343K
• ISSN：1520-510X

文摘

A variety of next-generation energy processes utilize the electrochemical interconversions of dioxygen and water as the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Reported here are the first estimates of the standard reduction potential of the O₂ + 4e^{鈥?/sup> + 4H+ 鈬?2H₂O couple in organic solvents. The values are +1.21 V in acetonitrile (MeCN) and +0.60 V in N,N-dimethylformamide (DMF), each versus the ferrocenium/ferrocene couple (Fc+/0) in the respective solvent (as are all of the potentials reported here). The potentials have been determined using a thermochemical cycle that combines the free energy for transferring water from aqueous solution to organic solvent, 鈭?.43 kcal mol鈥? for MeCN and 鈭?.47 kcal mol鈥? for DMF, and the potential of the H+/H₂ couple, 鈥?0.028 V in MeCN and 鈭?.662 V in DMF. The H+/H₂ couple in DMF has been directly measured electrochemically using the previously reported procedure for the MeCN value. The thermochemical approach used for the O₂/H₂O couple has been extended to the CO₂/CO and CO₂/CH₄ couples to give values of 鈭?.12 and +0.15 V in MeCN and 鈭?.73 and 鈭?.48 V in DMF, respectively. Extensions to other reduction potentials are discussed. Additionally, the free energy for transfer of protons from water to organic solvent is estimated as +14 kcal mol鈥? for acetonitrile and +0.6 kcal mol鈥? for DMF.}