Localized growth of atomic-layer-deposited platinum catalysts on plasma-treated surface of carbon nanotubes

Platinum–carbon nanotube (CNT) catalysts were evaluated for use as the cathode catalyst in polymer electrolyte membrane fuel cells. Pt catalysts were fabricated by atomic layer deposition (ALD) on bare untreated or O₂ plasma treated CNTs. Pt formed as particles that uniformly covered both the bare and plasma-treated CNT supports. The Pt particles on the bare CNTs were relatively small, and the particle size increased with increasing number of ALD cycles. By contrast, Pt formed as sparsely deposited large particles on the plasma-treated CNTs. This morphological difference caused a clear difference in the electrochemical and fuel cell performance. Experiments confirmed that relatively high and stable power production can be obtained using the relatively large Pt catalysts grown on the plasma-treated CNTs. Factors other than electrochemical enhancement by the geometric features were also found to affect the fuel cell performance.