Detailed optimization of multiwall carbon nanotubes doped microporous layer in polymer electrolyte membrane fuel cells for enhanced performance

Polymer electrolyte membrane fuel cell is a promising renewable energy technology. In order to further enhance the output performance improvement caused by the doping of multiwall carbon nanotubes in microporous layers, in this study, detailed optimization of microporous layers containing multiwall carbon nanotubes is accomplished. The synergy effects of carbon powder types, contents and diameters of multiwall carbon nanotubes, and microporous layer loadings are considered for the first time. The optimal composition under different humidity is obtained. It is found that among the four factors, carbon powder types have the greatest impact on the performance. The fuel cells containing thick multiwall carbon nanotubes exhibit more stable performance with the change of humidity. Microporous layers with large content of multiwall carbon nanotubes (15 wt%) promise better performance. The performance of microporous layer with the carbon powder of XC-72 is the worst due to inferior mass transfer and increased ohm resistance. The fuel cell with the optimized microporous layer exhibits excellent performance, under the temperature of 80 degrees C and 0.8 bar back pressure, the current density at 0.6 V is up to 1900 mA/cm(2), and the max power density reaches 1180 mW/cm(2). The significant improvement of performance can be attributed to favorable porous structure along with enhanced mass transfer and improved conductivity.