Low energy plasma treatment of a proton exchange membrane used for low temperature fuel cells

A low energy (∼30 V) plasma treatment of Nafion, a commercial proton exchange membrane used for low temperature fuel cells, is performed in a helicon radiofrequency (13.56 MHz) plasma system. For argon densities in the 10 ⁹-10¹⁰ cm^-3 range, the water contact angle (hydrophobicity) of the membrane surface linearly decreases with an increase in the plasma energy dose, which is maintained below 5.1 J cm^-2, and which results from the combination of an ion energy dose (up to 3.8 J cm ^-2) and a photon (mostly UV) energy dose (up to 1.3 J cm ^-2). The decrease in water contact angle is essentially a result of the energy brought to the surface by ion bombardment. The measured effect of the energy brought to the surface by UV light is found to be negligible.