Tuesday, July 27, 2010

Membrane Fuel Cell Electrodes Incorporated With Carbon Nanomaterial-Supported Electrocatalysts

The Atomic Energy Council (Taoyuan, TW) garnered U.S. Patent 7,763,374 for fuel cell electrodes that are fabricated on electrode base substrates. The electrode substrates can be evenly and uniformly covered with electrocatalysts, which are supported on carbon nanomaterials, and ionomers by means of filtration and pressing. The electrodes can be used as anodes or cathodes for membrane fuel cells, such as DMFC and PEMFC, according to inventors Su-hsine Lin, Shean-du Chiou, Wan-min Huang and King-tsai Jeng.

The Atomic Energy Council’s method for fabricating electrodes, having electrochemical nano-catalysts supported on carbon nanomaterials, for use in membrane fuel cells comprising the steps of: (a) Adding an electrochemical nano-catalyst synthesized on a carbon nanomaterial with an ionomer solution and a solvent together in a container; (b) Obtaining a well-mixed electrocatalyst mixture through a supersonic oscillation and a speedy stirring; (c) Depositing an electrode base substrate on a funnel of a filtering device and pouring said electrocatalyst mixture on the electrode base substrate for filtering out an electrocatalyst layer and thus obtaining a filtrate; (d) Re-filtering the filtrate for several times until obtaining a limpid liquid; (e) Obtaining said coated electrode base substrate to be covered with a plastic film and then to be pressed under a pressure at a room temperature; and (f) Drying the electrode substrate to obtain an electrode for a membrane fuel cell (MFC). 

A membrane fuel cell (MFC) can be a direct methanol fuel cell (DMFC) or a hydrogen proton exchange membrane fuel cell (PEMFC), which is an electrochemical energy conversion, or power generation, device using a proton exchange membrane (PEM), e.g., Nafion 117, as a solid polymer electrolyte (SPE). Such a fuel cell belongs to an acid-type membrane fuel cell, which needs to use corrosion-resistant electrocatalysts of platinum group, e.g., Pt (platinum) and Pt--Ru (platinum-ruthenium). Also, there is an alkaline-type membrane fuel cell incorporated with an anion exchange membrane (conducting OH.sup.--), e.g., AHA membrane of Tokuyama, Japan, as an SPE, which is able to use low-cost electrocatalysts of non-platinum group, such as Fe--Ni (iron-nickel) and Fe--Co--Ni (iron-cobalt-nickel), under a less corrosive environment. 

The main purpose of  the Atomic Energy Council’s invention is to fabricate electrodes using electrochemical nano-catalysts supported on carbon nanomaterials, and the electrodes are used as anodes or cathodes of acid-type, or alkaline-type, membrane fuel cells according to the compositions of the electrochemical nano-catalysts.

To achieve the above purpose, the inventors devised methods for fabricating  fuel cell electrodes using various electrocatalysts supported on a variety of carbon nanomaterials. These electrode fabrication methods comprise common steps for each method, including: (a) adding a carbon nanomaterial-supported electrochemical nano-catalyst, an ionomer solution, and a solvent together; (b) obtaining a well-mixed electrocatalyst mixture through a supersonic oscillation and a high-speed stirring; (c) depositing an electrode base substrate on a funnel of a filtering device and pouring the electrocatalyst mixture into the funnel for filtering out the electrocatalyst on the electrode base substrate and, at the same time, obtaining a filtrate; (d) re-filtering the collected filtrate for several times until obtaining a clear liquid; (e) obtaining the electrode base substrate to be covered with a plastic film and then to be pressed under room temperature; and (f) drying the electrode substrate in air to obtain an electrode for a membrane fuel cell. The method for fabrication of an electrode with a uniform catalyst layer containing a carbon nanomaterial-supported electrocatalyst and an ionomer is obtained. 


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