Functionalized Carbon Nanotube Dispersion in a Nation Composite Membrane for Proton Exchange Membrane Fuel Cell Applications

摘要

Functionalized multiwalled carbon nanotube (f-MWCNT) reinforced Nation nanocomposite membranes were prepared and characterized for proton exchange membrane (PEM) fuel cell applications. To enhance the carbon nanotube dispersion in a Nation membrane, oxidized MWCNTs (ox-MWCNTs) and sulfonated MWCNTs (s-MWCNTs) were prepared via chemical reactions, using 60% nitric acid for the ox-MWCNTs and 98% sulfuric acid for the s-MWCNTs, respectively. Then 1 wt.% ox-MWCNTs or s-MWCNTs, based on Nation polymer weight, were added in the Nation solution. In the solution casting procedure, a certain amount of deionized (DI) water within the range of 10-60% content was intentionally added to the ox-MWCNT/Nafion or s-MWCNT/Nafion solution to enhance the f-MWCNT dispersion in the nanocomposite membranes. The degree of dispersion of the ox-MWCNTs and s-MWCNTs in the Nation nanocomposite membranes was dramatically enhanced by increasing the water content in the solution-casting procedure. For the ox-MWCNT dispersion, the ox-MWCNT/Nafion solution with over 60% water content produced well-dispersed ox-MWCNT/Nafion nanocomposite membranes, and for the s-MWCNT dispersion, the s-MWCNT/Nafion solution with over 40% water content produced well-dispersed s-MWCNT/Nafion nanocomposite membranes. The additional water, 10-60% content, in the f-MWCNT/Nafion solution could prevent the self-assembly of the f-MWCNTs in the solution-casting procedure by adjusting the evaporation rate of the solvent in the solution. Then the well-dispersed f-MWCNT/Nafion nanocomposite membranes were prepared. The prepared well-dispersed f-MWCNT/Nafion nanocomposite membranes showed enhanced thermal properties within the range of 30-300℃ as well as lower methanol uptake values without changing their ion exchange capacity.