Effects of Surface Structures and Hydrophobic Species on the Oxygen Reduction Reaction Activity of Pt 3 Fe Single-Crystal Electrodes

The oxygen reduction reaction (ORR) on the low-index planes of Pt 3 Fe in O 2 -saturated 0.1 M HClO 4 is studied using the hanging-meniscus rotating-disk electrode method. The ORR activity increases as follows: Pt 3 Fe (100) < Pt 3 Fe (110) < Pt 3 Fe (111). The ORR activity of Pt 3 Fe (111) is 20 times higher than that of Pt (111). The ORR activities on the low-index planes of Pt 3 Fe are improved by modifying the electrodes with hydrophobic species, such as the tetra- n -hexylammonium (THA + ) cation, melamine, and the protonic ionic liquid [7-methyl-1,5,7-triazabicyclo[4.4.0] dec-5-ene] [bis(pentafluoroethylsulfonyl)imide]. The ORR activity of melamine-modified Pt 3 Fe (111) is 1.4 times higher than that of bare Pt 3 Fe (111). Graphical abstract