Development of restacking inhibited graphene-based cathode catalysts for polymer electrolyte membrane fuel cells

Abstract

Graphene with a two-dimensional layer structure of $sp_2-hybridized$ carbon has enabled considerable progress of energy conversion and storage technologies. In polymer electrolyte membrane fuel cells (PEMFCs), however, graphene layers are easily restacked and agglomerated to graphite. In terms of catalysis, re-stacking of graphene inhibits efficient transport of reactants between the graphene layers. Thus, further development of graphene technology should be pursued for applications related to catalysts. Herein, a $MnO_2$-polyaniline/reduced graphene oxide (M-PANI/rGO) was synthesized via a chemical oxidative polymerization of aniline by addition of $MnO_2$. The $MnO_2$ as a self-sacrificial template was introduced to prevent the re-stacking of GO. For comparison, polyaniline/reduced graphene oxide (PANI/rGO) was prepared by conventional polymerization using $(NH_4)_2S_2O_8$ as the oxidant. Physical characterizations reveal that the M-PANI/rGO effectively disturbs re-stacking of graphene layers, which induced facile transport of reactants on the graphene basal plane. When these two samples were applied as oxygen reduction reactions (ORRs) catalyst for PEMFCs, the onset potential of M-PANI/rGO is measured to be 0.88 V, while that of PANI/rGO is 0.70 V. We anticipate that, in the fields of fuel cell, this work can provide several insights to application of the catalysts to be in the graphene-based design for ORRs.