Porous electrodes based on Ti, Zr and Co oxides for electrochemical oxygen sensors
Advancing the chemical engineering fundamentals
Electrochemical Engineering (T2-14P)
Keywords: Oxygen electroreduction, Electrochemical oxygen sensors, Ti, Zr, Co oxides nanoparticles
Porous electrodes based on Ti, Zr and Co oxides
for electrochemical oxygen sensors
G.Ya. Kolbasov, V.S. Vorobetz , N.D. Ivanova, O.A. Stadnik
Institute of General & Inorganic Chemistry,
32-34 prospekt Palladina, 03680 Kiev 142, Ukraine,
The porous electrodes based on Ti, Zr and Co oxides were obtained. TiO2 nanoparticles were produced by sol-gel method on a Ti substrate from solutions containing titanium chloride. The nanoparticles of mixed TiO2 - ZrO2 oxides were produced by sol-gel method on a Ti substrate from solutions containing titanium and zirconium tetraisopropoxides. The electrodes were annealed in air at 350-4500C. The cobalt oxide compounds of nonstoichiometric composition were obtained on a Ni anode by the electrooxidation of Со2+ ions from an electrolyte containing СоSO4 and NH4F. The cobalt oxide compounds had the composition СохОу(ОН)z, where х=0.65–0.71, у=1.34–1.79, z=1.3–1.52. The average size of nanoparticles on the Ti surface depended on the deposition conditions, and was no more thаn 10 nm, the average thickness of the deposited layers was 300 – 1500 nm. The cobalt oxide particles size was 80-120 nm; the coating thickness was 2-3 μm.
Catalytic properties of electrodes were investigated in the processes of oxygen electroreduction in physiological solution of NaCl (0,9%) and in blood plasma. The polarization curves for all electrodes exhibited one current wave, which corresponded to oxygen reduction limiting current. We have found that the overall O2 reduction process involves two electrons, and that the reaction proceeds without hydrogen peroxide formation. It has been found for the TiO2 - ZrO2 oxides that the potential of oxygen reduction shifts more negative values with increasing ZrO2 content. The layers which contained 5-10% ZrO2 were most stable in time. For the Co oxides, increasing the NH4F content of the starting solution from 20 to 40 g/l enhanced the electrocatalytic properties of the electrodes, reducing by ≈200 mV the oxygen reduction overpotential as against that at the Ni substrate.
The relative change in conduction band potential and valence band potential of TiO2-ZrO2 electrodes has been determined from photoelectrochemical measurements [1] depending on the film composition . It has been found that the conduction band potential of electrodes did not vary, but the valence band potential increased in anodic region with increasing ZrO2 content, which accounts for the improvement of their oxidative properties. The shift of the oxygen reduction potential to cathodic region for the electrodes with high ZrO2 content we associate with a change in their catalytic activity.
The electrodes investigated were distinguished by a high sensitivity to dissolved oxygen ((4-5)∙10-6 g/l) and high reproducibility of characteristics in long-time cycling. These electrodes promise much as reusable electrode materials in electrochemical sensors for the determination of oxygen concentration.
Keywords: Oxygen electroreduction, Electrochemical oxygen sensors,
Ti, Zr, Co oxides nanoparticles
Reference:
[1] N. Smirnova, Y. Gnatyuk, A. Eremenko, G. Kolbasov, 8th International Conference on
Solar Energy and Applied Photochemistry, 20 – 25 February 2005, Luxor, Egypt. Book
of Abstracts, p. 100-101
Presented Wednesday 19, 13:30 to 15:00, in session Electrochemical Engineering (T2-14P).
