In addition, the distribution of ionomer on the surfaces both of Pt particles and carbon particles is another key point for the design of high performance cathode CLs, because the transport of species such as O2 and protons (Hþ) related to the ORR is controlled by the thickness of the ionomer on the catalyst surface, as well as the continuity of the ionomer and gas networks in the CL, with the transport of electrons being related to the continuity of the carbon particle network [6,7].