Revisiting the Redox Properties of Hydrous Iridium Oxide Films in the Context of Oxygen Evolution
Journal article, 2013

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.

Author

Patrick Steegstra

University of Gothenburg

Michael Busch

University of Gothenburg

Itai Panas

Chalmers, Chemical and Biological Engineering, Environmental Inorganic Chemistry

Elisabet Ahlberg

University of Gothenburg

Journal of Physical Chemistry C

1932-7447 (ISSN) 1932-7455 (eISSN)

Vol. 117 40 20975-20981

Areas of Advance

Nanoscience and Nanotechnology (2010-2017)

Energy

Materials Science

Subject Categories

Materials Chemistry

Theoretical Chemistry

Nano Technology

DOI

10.1021/jp407030r

More information

Created

10/7/2017