Integrated plasma synthesis of efficient catalytic nanostructures for fuel cell electrodes

A single plasma process involving three consecutive steps has been developed for producing high gas flow catalytic nanostructures on the electrodes of proton exchange membrane (PEM) fuel cells (FC). Using a high density helicon radio frequency (13.56 MHz) plasma, nickel is sputtered onto a porous carbon support. Changing the background gas from argon to methane/hydrogen allowed 2 μm long, 37 nm diameter carbon nanofibres (CNFs) to be grown by diffusion through the nickel clusters in a ‘tip growth’ mechanism at the relatively low temperature of 400 ◦C. The third step involves plasma sputtering of platinum onto the CNFs, resulting in nanoclusters (3–8 nm) being formed on the periphery of the CNFs. Four FC cathodes were synthesized on carbon paper and PTFE/carbon loaded cloth (known as gas diffusion layer, GDL), both with and without CNFs, with the Pt/CNFs nanostructures grown on PTFE/carbon loaded cloth having the best FC performances. Compared with conventional FCs, the efficiency of sputtered platinum in the Pt/CNF based cathode is much higher than in a chemically deposited system over the entire range of operating current. This indicates that combination of different, simple, plasma techniques is an effective method for preparing highly efficient catalyst layers. (Some figures in this article are in colour only in the electronic version)