Heterogenous Superhydrophobicity where an air layer is trapped between the liquid and the solid surface. This air layer prevent water from touching the solid surface. The microsized papillae that contains billions of these nanosized branch like protrusion.
The oxygen reduction reaction in the cathode catalyst layer occurs at the triple phase boundary (TPB). The reaction occurs at TPB where air supply the oxygen, water supply protons and the solid platinum provides the electrons necessary for the reaction. O2 ---- 4 protons + 4 electrons + 2 water molecules. For a catalyst layer that has heterogenous Superhydrophobic structure , each nanosized branch like protrusion acts as a TPB site.