Graphene-Wrapped Nanoporous Nickel-Cobalt Oxide Flakes for Electrochemical Supercapacitors

A novel approach for hybridizing nanoporous NiCo oxide flakes with graphene sheets is reported. Positively charged cyano-bridged CoNi coordination polymer flakes (CoNi-CP) are mixed with graphene (G) suspension with negatively charged surface. Due to effective electrostatic interaction, both the materials are hybridized to form CoNi-CP/G composite. The as-prepared CoNi-CP/G composite is thermally treated in air, to remove the organic components without affecting the integrity of the parent G sheets. Through the thermal treatment, the CoNi-CP flakes wrapped into G sheets are converted to NiCo oxide, resulting in a new composite consisting of NiCo oxide flakes and G sheets. The NiCo-oxide/G composite shows the high specific capacitance (similar to 199 F g-1) at 5 mV/s, and features the good capacitance retention of similar to 68% at 100 mV(similar to 135 F g(-1)).