Preparation of a Ag–MnO2/graphene composite for the oxygen reduction reaction in alkaline solution

Abstract

Ag–MnO₂/graphene composite with mesoporous structure is prepared by an immersion-calcination method. The composite composed of Ag (∼6 nm) and MnO₂ (∼4 nm) nanoparticles is distributed evenly on the graphene sheets. The oxygen reduction peak of the Ag–MnO₂/graphene catalyst in a 0.1 M KOH solution is tested at −0.15 V, which is more positive than that of 20% Pt/C (−0.19 V). The onset potential of Ag–MnO₂/graphene (0.068 V) is close to Pt/C (0.079 V). The oxygen reduction reaction limiting current density for the Ag–MnO₂/graphene catalyst is approximately 5.62 mA cm⁻², which is similar to that for Pt/C (5.83 mA cm⁻²). The onset potential of the Ag–MnO₂/graphene is close to that of Pt/C. The introduction of Ag nanoparticles between the MnO₂ nanoparticles on graphene sheets can significantly improve the catalytic activation, because of the increase in conductivity and abundant active sites provided during the ORR process.