Kinetic and Mechanistic Studies of the Electrocatalytic Reduction of O2 to H2O with Mononuclear Cu Complexes of Substituted 1,10-Phenanthrolines

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• 作者：Charles C. L. McCrory ; Xavier Ottenwaelder ; T. Daniel P. Stack ; Christopher E. D. Chidsey
• 刊名：Journal of Physical Chemistry A
• 出版年：2007
• 出版时间：December 13, 2007
• 年：2007
• 卷：111
• 期：49
• 页码：12641 - 12650
• 全文大小：289K
• 年卷期：v.111,no.49(December 13, 2007)
• ISSN：1520-5215

文摘

Mononuclear Cu complexes with a 1,10-phenanthroline-based ligand adsorbed onto an edge-plane graphiteelectrode act as electrocatalysts for the 4-electron reduction of O₂ to H₂O. A mechanism is proposed for theelectrocatalytic O₂ reduction that accounts for the observed redox and kinetic dependences on coordinatinganions and proton donors in the buffer. Systematic increases of ligand electron-withdrawing properties and/or the steric demands near the Cu center increase the E⁰ of the Cu catalysts but decrease the rate of O₂reduction. The kinetic rate of O₂ reduction at E⁰, reported as kinetic current divided by catalyst redox charge,decreases as E⁰ increases: from 16 s^-1 measured at E⁰ in air-saturated solutions for adsorbed Cu(phen) to 0.4s^-1 for Cu(2,9-Et₂-phen). The maximum value of E for which catalytic activity can be attained is estimatedto be +350 mV vs NHE. Near E⁰, the kinetic current deviates from that expected if O₂ binding were the solerate-limiting step. This indicates that one or more of the electrochemical reduction steps are rate limiting atpotentials near E⁰.