Fig xA Polarization and power
Fig. 4. Polarization and power density plots at 70 °C of the PEMFCs using: the 50 wt% Pt–carbon black cathode (0.2 mg Pt/cm2) (curve a), the 50 wt% Pt–graphene/MWCNT composite cathode (0.13 mg Pt/cm2) (curve b) and the 50 wt% Pt–graphene cathode (0.13 mg Pt/cm2) (curve c).Reproduced with permission from .Figure optionsDownload full-size imageDownload as PowerPoint slide
In  the authors showed that the Pt–graphene/MWCNT composite cathode could be used instead of the Pt–carbon black cathode in PEMFCs. However, as is presented in Fig. 4 the power density for PEMFCs with Pt–graphene/MWCNT composite cathode was slightly lower than for fuel PRT 062607 without graphene/MWCNT in the cathode. On the other hand for PEMFCs with Pt–graphene cathode (see Fig. 4 curve c) the power density was significantly lower than for PEMFCs with Pt–carbon black and Pt–graphene/MWCNT composite cathode.
Relevant conclusions may be found in Park’s work  where catalyst ink was fabricated by ultrasonication of particular substrates and solvents, i.e. carbon black, Nafion solution, water and methanol. In this case the ESA for Pt nanoparticles dispersed on graphene sheets was increased with a higher content of carbon black. The same observation was seen for mass activity and performance, as immunoglobulins are ca. 3.9 times and 65% better, respectively, based on polarization curves. As the authors summarized, highly wrinkled and rearranged graphene sheets with the addition of carbon black improve the Pt utilization for ORR .