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Abstract

The Oxygen and nitrogen plasma treatment were applied to produce graphene with abundant edges, oxygen functional groups, and nitrogen doping. The plasma-etched graphene was then used as a metal-free electrocatalyst in a solid acid fuel cell. Scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy were used to characterize the graphene layers. Alternating-current impedance spectroscopy of a hybrid electrode containing the plasma-etched graphene and cesium dihydrogen phosphate as proton-conducting solid acid illustrated its remarkable catalytic activity under cathodic conditions. Thus, both O₂ and N₂ plasma treatment activated the material. While O₂ plasma was a more effective activator than N₂ plasma, it also resulted in higher degradation rates. A combination of density functional theory calculations and experimental results indicated that zigzag carbon was the most active site for the oxygen reduction reaction on both O₂ and N₂ plasma-etched graphene. Furthermore, the armchair carbons adjacent to the surface oxygen groups and doped heteroatoms were also important active sites for O₂ and N₂ plasma-etched graphene, respectively. The results of this study will guide future endeavors in the development of non-precious metal catalysts for use as fuel cell cathodes.