Hitachi Maxell, Ltd. (TSE: 6810) has announced development of a new catalyst used for oxygen-reduction reactions at the cathode of a polymer electrolyte fuel cell (PEFC). The new catalyst is gold-platinum (AuPt) nano-particle 2 to 3 nm in size and can generate approximately 4.8 times the oxygen-reduction current per unit area than commercial platinum catalysts.
PEFCs are a promising clean-energy source for automobiles, homes, and mobile devices. Platinum is commonly used as the catalyst for the oxygen-reduction reaction in PEFCs, but platinum is an extremely expensive precious metal, so reducing material cost for PEFCs by minimizing the amount of platinum used, while improving its catalytic effect is an important R&D topic.
Increasing the surface area of the catalyst by reducing particle size is an effective way of improving catalytic activity. It has also been reported that the addition of base metals such as iron, cobalt and nickel to platinum also improves the oxygen-reduction reaction rate, but these kinds of base metals dissolve easily in the acidic environment of a PEFC where the catalyst is working, which is a problem.
Maxell has developed a new catalyst for oxygen-reduction reactions in PEFCs. The new catalyst is a composition of platinum and gold and is resistant to acidic environments. It was difficult to synthesize gold particles smaller than 5 nm due to its relatively low melting point, but by applying a proprietary nano-level particle synthesizing technology, Maxell has succeeded in developing a high-activity structure in which the gold and platinum are not fully alloyed for the new catalyst. Using citric acid as a reducing agent, AuPt catalyst particles 2 to 3 nm in size were synthesized at 373 K. Compared with platinum catalysts, this new AuPt catalyst achieves approximately 4.8 times higher oxygen-reduction current per unit area. X-ray diffraction analysis revealed that the gold and platinum are not fully alloyed and it is supposed that this structure results in the improved the oxygen-reduction reaction activity.
This success represents a large step closer to fuel cells that are practical for applications requiring large current, such as automobiles and homes.
Maxell presented this new technology for synthesizing a highly-active AuPt catalyst at the 101st catalysis conference held March 29 at the Tower Hall Funabori in Tokyo.
Maxell will continue nano-technology research and development towards practical applications in polymer-electrolyte and direct-methanol fuel cells.
About Hitachi Maxell
Since its foundation in 1960, Hitachi Maxell, Ltd. (TSE: 6810) has led the electronics industry at home and abroad in the fields of memory and mobility. Maxell is a leading manufacturer of information storage media products including magnetic tapes, optical disks, and battery products including lithium ion rechargeable batteries, micro batteries and dry cell batteries.