Research On Structure And Performance Of Special-shaped Direct Methanol Fuel Cell

DMFC(Direct methanol fuel cell) is considered as the most promising substitute of small portable power sources. Planar DMFC does not have the characteristic of self-storage fuel, and its fuel is supplied by complex external piping equipment; While special-shaped DMFC has the characteristics of self-storage fuel, suitable for making small power source units, and high volume power density. But presently only tubular structure DMFC has been reported, and has the difficulty in molding process.In order to overcome the current difficulty in molding tubular structure DMFC, a group of novel structure for MEA(Membrane electrode assemble) was put forward, including the U-MEA(“U” shaped cross section MEA), C-MEA(“C” shaped cross section MEA), and V-MEA(“V” shaped cross section MEA); The structural parameters of special-shaped MEA were identified. The special-shaped MEA was made up of six layers, anode Ti(titanium) mesh, anode catalyst layer, Nafion membrane, cathode catalyst layer, cathode gas diffusion layer and cathode Ti mesh; Then, three structure designs of special-shaped DMFC were finished, including U-DMFC(“U” shaped cross section DMFC), C-DMFC(“C” shaped cross section DMFC) and V-DMFC(“V” shaped cross section DMFC), which were composed of the base body, special-shaped MEA, sealing components, top body, head cover, plug and so on.Planar Ti mesh-based MEA was chosen as the research object, which was for the study of the effect about molding process conditions and work environment on the Ti mesh-based MEA performance. When the MEAs were molded by hot-pressing at 135 for 180 s with different pressure℃ s of 0 MPa, 2.5 MPa, 5 MPa, 7.5 MPa and 10 MPa, respectively, the maximum power density of Ti mesh-based MEA increases firstly, after the first peak, it gradually decreases along with the increase of molding pressure conditions, the maximum power density value appears at the molding pressure of 2.5 MPa under the condition of room temperature, and at the molding pressure of 5 MPa under the condition of 60℃; When the MEAs were molded by hot-pressing under 5 MPa for 180 s with different temperatures of 115℃, 135 and ℃155℃, respectively, the maximum power density of Ti mesh-based MEAs increases firstly, after the first peak, it gradually decreases along with the increase of molding pressure conditions, also, and the maximum power density appears at the molding temperature of 135℃; When the anode was supplied with 40 mL 1 mol·L-1 methanol & 0.5 mol·L-1 sulfuric acid aqueous solution under condition of air-breathing at room temperature, the Ti mesh-based MEA was discharged with constant current density of 10 mA·cm-2 by home-made experimental equipment for 45 hours steadily and continuously, whose Faraday efficiency can reach 33.46%.After being compared and analysed, the molding condition of special-shaped MEA was attained at 5 MPa for 180 s at 135℃. Then three kinds of special-shaped MEA were prepared by home-designed & home-made mold. Three kinds of special-shaped DMFC prototype were assembled with the home-designed & home-made shell together, whose performance was studied with anode electrolyte of 1mol·L-1 methanol & 0.5mol·L-1 sulfuric acid aqueous solution. The maximum power density of U-DMFC, C-DMFC and V-DMFC prototype is 6.48 mW·cm-2, 8.26 mW·cm-2 and 9.50 mW·cm-2 respectively under the condition of 0.1 MPa and 100 mL·min-1 oxygen at 60℃.