Effect of confined space reduction of graphite oxide followed by sulfur doping on oxygen reduction reaction in neutral electrolyte

Abstract

Graphite oxide was thermally reduced within the confined space of commercial silica gel, and then the matrix was removed. The modified graphite oxide was treated with hydrogen sulfide at 800 °C. The treatment applied results in a specific porous texture and high hydrophobicity of the surface. 3 at.% sulfur was introduced, mainly as thiophenic groups and sulfur in aromatic rings. The reduced GO and sulfur doped was evaluated as oxygen reduction catalysts in neutral electrolytes. Even though both materials show the strong catalytic activity, the results indicate that more electrons take part in oxygen reduction reaction on reduced GO than on its sulfur modified counterpart. The high activity of our materials is linked to oxygen and surface functional groups incorporated to the graphene structure, to the high degree of surface hydrophobicity and to the specific texture consisting of micro and mesopores (replicate of silica porosity).