Bifunctional effect of reduced graphene oxides to support active metal nanoparticles for oxygen reduction reaction and stability

Highly active and stable Pt/reduced graphene oxide (RGO) electrocatalysts for the application of proton exchange membrane fuel cells were developed by tuning the O/C atom ratio of RGO supports. The results showed that Pt nanoparticles with a narrow distribution of particle sizes were well dispersed on RGO, and an increased conductivity and stability of RGO were achieved when the Pt/RGO was deoxidized with an increased graphitization degree of RGO during hydrogen reduction. The highest activity of oxygen reduction reaction (ORR) and stability of Pt/RGO was obtained by hydrogen heat treatment Pt/RGO for 1 hour, in which the O/C atom ratio was 0.14. However, with increment of the reaction time, the atom ratio of O/C decreased to 0.11, the performance dropped sharply due to the further removal of the oxygenated groups on RGO, resulting in a serious aggregation of Pt nanoparticles. This study strongly suggested a bifunctional effect of both graphitization and the oxygenated groups on the catalytic activity and stabilization of metal (such as Pt) nanoparticles on RGO. This will open a door to apply graphene in fuel cells and other fields.