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Revisiting the Redox Properties of Hydrous Iridium Oxide Films in the Context of Oxygen Evolution

Patrick Steegstra ; Michael Busch ; Itai Panas (Institutionen för kemi- och bioteknik, Oorganisk miljökemi) ; Elisabet Ahlberg
Journal of Physical Chemistry C (1932-7447). Vol. 117 (2013), 40, p. 20975-20981.
[Artikel, refereegranskad vetenskaplig]

The electrochemistry of hydrous iridium oxide films (HIROF) is revisited. Cyclic voltammograms of HIROFs display two reversible redox couples commonly assigned to the Ir(III)/Ir(IV) and Ir(IV)/Ir(V) transitions, respectively. However, compared to the first, the second redox couple has significantly less charge associated to it. This effect is interpreted as partial oxidation of Ir(IV) as limited by nearest neighbor repulsion of resulting Ir(V) sites. Thus, the redox process is divided into two steps: one preceding and one overlapping the oxygen evolution reaction (OER). Here, the ``super-nernstian'' pH dependence of the redox processes in the HIROF is used to expose how pH controls the overpotential for oxygen evolution, as evidenced by the complementary increased formation of Ir(V) oxide. A recently formulated binuclear mechanism for the OER is employed to illustrate how hydrogen bonding may suppress the OER, thus implicitly favoring Ir(V) oxide formation above the thermodynamic onset potential for the OER at low pH.



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Denna post skapades 2013-09-12. Senast ändrad 2016-12-05.
CPL Pubid: 183149

 

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Institutioner (Chalmers)

Institutionen för kemi och molekylärbiologi (GU)
Institutionen för kemi- och bioteknik, Oorganisk miljökemi (2005-2014)

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Energi
Materialvetenskap
Nanovetenskap och nanoteknik
Materialkemi
Elektrokemi
Kvantkemi
Nanoteknik

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