Electrochemical synthesis of a nanohybrid film consisting of stacked graphene sheets and manganese oxide as oxygen evolution reaction catalyst
A new electrochemical process yielded a thin film consisting of stacked graphene (GR) sheets and manganese oxide. The process involved anodic deposition of manganese oxide nuclei on an electrode substrate and on the surface of GR sheets through electrolysis of aqueous Mn2+ ions in the presence of cationic GR colloids modified with poly(diallydimethylammonium) (PDDA+ followed by extraction of the PDDA. The catalytic activity of Mn oxide for the oxygen evolution reaction in an alkaline electrolyte was dramatically enhanced by hybridizing it with GR; an onset overpotential of 335 mV and a Tafel slope of 58 mV per decade were observed with excellent stability. These results can be attributed to a synergistic effect of the catalytic activity of nanosized Mn oxide deposits and the ability of GR to transfer electrons from the catalysts.