Thermodynamic driving force effects in the oxygen reduction catalyzed by a metal-free porphyrin

0380420 - ÚFCH JH 2013 RIV GB eng J - Článek v odborném periodiku
Trojánek, Antonín - Langmaier, Jan - Samec, Zdeněk
Thermodynamic driving force effects in the oxygen reduction catalyzed by a metal-free porphyrin.
Electrochimica acta. Roč. 82, SI (2012), s. 457-462. ISSN 0013-4686. E-ISSN 1873-3859
Grant CEP: GA ČR GAP208/11/0697
Výzkumný záměr: CEZ:AV0Z40400503
Klíčová slova: oxygen reduction * metal-free porphyrin * electrocatalysis
Kód oboru RIV: CG - Elektrochemie
Impakt faktor: 3.777, rok: 2012

Cyclic voltammetry and the stopped-flow kinetic measurements are used to investigate the thermodynamic driving force effects in the molecular oxygen reduction with the methyl (Me)-substituted ferrocenes MenFc (n = 0, 2, 4, 6, 8, 10) at the polarized water|1,2-dichloroethane (DCE) interface and in the homogeneous DCE phase, which is catalyzed by 5,10,15,20-meso-tetraphenylporphyrin (H2TPP) dissolved in DCE. Ferrocene derivatives are characterized by their reversible half-wave potentials View the MathML source which are inferred from cyclic voltammetric data, and by the coresponding formal potentials E′0(SHE,o) referenced to the standard hydrogen electrode in DCE. It is shown that the reduction of the activated oxygen with MenFc is the rate-determining step in both electrochemical and chemical catalytic cycles. Plots of the logarithm of the rate constant of the catalyzed, non-catalyzed and electrocatalyzed oxygen reduction vs. the reversible half-wave potential for the MenFc+/MenFc redox couples in DCE have approximately the same slopes. Their values correspond to the Brønsted coefficient of about 1/2, which is characteristic for reactions with the symmetric activation barrier. A comparison of rates of the catalyzed and non-catalyzed oxygen reduction points to the inhibitory effect of water in the former case. Observed difference between the rates of the catalyzed and electrocatalyzed oxygen reduction was ascribed to the inhibitory effect of the present counteranion.
Trvalý link: http://hdl.handle.net/11104/0215761