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

Ag-MnO2/graphene composite with mesoporous structure is prepared by an immersion-calcination method. The composite composed of Ag (similar to 6 nm) and MnO2 (similar to 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.