Ruthenium Oxide Nanofiber Network Boosts Power for Fuel Cells and Supercapacitors Say Korea Institute of Science and Technology Researchers

Korean scientists have created a new nanofabrication process to more easily produce nanometer ruthenium oxide fibers for fuel cells, supercapacitors and electrodes for waste water treatment. 

U.S. Patent Application 20100002357, FIG. 5b shows a scanning electron microscope (SEM) image of a Korea Institute of Science and Technology (KIST) ruthenium oxide (RuO₂₎ nanofiber at times.150,000.  The material improves electrode performance for a wide range of applications.

Korea Institute of Science and Technology (KIST) (Seoul, KR) have found a simpler way to produce nanometer ruthenium oxide for fuel cell catalysts, electrodes for  wastewater treatment, conductive electrodes an d super capacitors.

In KIST scientists Il Doo Kim, Jae-Min Hong, Seong Mu Jo and Dong Young Kim relates to a porous conducting metal oxide electrode prepared by depositing a porous conducting metal oxide film comprised of a conducting metal oxide film layer with a network structure of nanofibers.  The network is comprised of nanograins or nanoparticles.

The nanoparticles are deposited on the surface of a current collector through the constant current method or the cyclic voltammetric method.  The process results in a high-speed charge/discharge and ultrahigh-capacity supercapacitor using the porous conducting metal oxide electrode.

Ruthenium oxide (RuO₂), a conducting metal oxide, is a transition metal oxide with a tetragonal rutile structure.  It has especially good thermal and chemical resistance and superior electrical conductivity in spite of being an oxide.  It has been widely used as an alternative for a metal electrode, a sensor, a catalyst, and the like.

Recently, research has been actively carried out on the electrochemical wastewater treatment utilizing electrolytic oxidation of insoluble oxide catalyst electrodes as DSA (dimensionally stable anode).  To improve the efficiency of pollutant oxidation, researches have been focused on the use of an anode prepared by forming a ruthenium-tin or iridium-tin oxide layer on titanium. 

Further, research on the application of electrochemical capacitors has been also carried out actively with the intent of increasing the power of high-density, high-output energy storage systems.  

A process enabling a simple large-scale production of ruthenium oxide with a network structure of ultrafine nanograins and/or nanoparticles having a size of 5 to 30 nanometers is becoming more and more important, say the KIST researchers.

If it is possible to increase specific surface area of ruthenium oxide (RuO₂) having superior electrical conductivity through such a simple process, superior characteristics can be attained in in various applications, including:  electrode of supercapacitor, catalyst for DMFC, sensor, insoluble oxide catalyst electrode, conductive electrode, and the like.

This can be attained with any conducting metal oxide having superior conductivity. That is, ruthenium oxide as well as conductive electrode materials having a conductivity of >0.1 S/cm. (IrO_x, NiO_x) may be utilized as electrode material for conductive electrodes and supercapacitors.

To this end, it is important to attain a nanofiber network structure of a metal oxide, including ruthenium oxide, IrO_x and NiO_x to significantly increase specific surface area and realize a porous structure. 

FIG. 1 schematically shows a process of preparing  ruthenium oxide having a network structure of nanograins and nanoparticles according to KIST inventors. 

FIG. 2 schematically shows an electrospinning apparatus used developed by KIST scientists.

FIG. 3a shows a scanning electron microscopic (SEM) image of a RuO₂/PVAc composite fiber prepared by electrospinning a mixture solution of a precursor capable of forming RuO₂ (ruthenium oxide) via heat treatment and PVAc (polyvinyl acetate, molecular weight=1,000,000) on a current collector, and FIG. 3b shows an enlarged view of the RuO.sub.2/PVAc composite fiber of FIG. 3a (FIG. 3a at .times.2,000 magnification.    

FIG. 4a shows an SEM image of a RuO₂ nanofiber prepared by heat treating the RuO₂/PVAc composite fiber at 450.degree. C. without heat compressing, in accordance with the and FIG. 4b shows an enlarged view of the RuO₂ nanofiber (FIG. 4a at .times.10,000 magnification

FIG. 5a  shows SEM images of a RuO₂ nanofiber prepared by heat treating the RuO₂/PVAc composite fiber at 450.degree. C. without heat compressing (FIG. 5a at .times.80,000 magnification.