Cathode catalyst layer with stepwise hydrophobicity distribution for a passive direct methanol fuel cell

A novel cathode catalyst layer with discontinuous hydrophobicity gradient distribution is designed and fabricated for passive direct methanol fuel cells (DMFCs). The stepwise hydrophobicity distribution is beneficial to the oxygen diffusion inside the cathodic catalytic layer and to the water removal from the cathode, thus improving the performance and stability of the DMFC. The DMFC with the above-mentioned novel cathodic catalytic layer structure presents a maximum power density of 33.5 mW cm ^-2 at a temperature of ca. 25 °C, while the DMFC with a conventional structure only gives 27.4 mW cm ^-2 under the same operating conditions. The enhanced performance of the DMFC with such a novel cathode structure might be attributed to a decreased charge-transfer resistance for the oxygen reduction reaction on the cathode.