cm3012205_si_001.pdf (1.06 MB)
Electrodeposition of Crystalline Co3O4A Catalyst for the Oxygen Evolution Reaction
journal contribution
posted on 2012-09-25, 00:00 authored by Jakub
A. Koza, Zhen He, Andrew S. Miller, Jay A. SwitzerCrystalline films of Co3O4 are
deposited
by electrochemically oxidizing a tartrate complex of Co2+ in an aqueous, alkaline solution at elevated temperatures. The crystallinity
and stability of the films are a strong function of the deposition
temperature. Films deposited at temperatures from 50 to 90 °C
are amorphous, but films deposited from refluxing solution at 103
°C are crystalline. The crystalline films adhere strongly to
the substrate, whereas the amorphous films peel off of the substrate
when dried due to drying stresses. The crystalline films deposit with
the normal spinel structure, with a lattice parameter of 0.8097 nm
and crystallite size of 26 nm. The catalytic activity of Co3O4 for the oxygen evolution reaction (OER) of the crystalline
and amorphous films is compared by Tafel analysis in alkaline solution
at pH 14. The crystalline Co3O4 film has a Tafel
slope of 49 mV/decade and an exchange current density of 2.0 ×
10–10 A cm–2, whereas an amorphous
film deposited at 50 °C has a Tafel slope of 36 mV/decade and
an exchange current density of 5.4 × 10–12 A
cm–2. Because the films deposited from refluxing
electrolyte deposit directly as crystalline films, it is possible
to deposit them epitaxially on single-crystal Au(100). This opens
up the possibility to study the catalytic activity of different Co3O4 planes exposed to the electrolyte.