Controlled synthesis of ordered sandwich CuCo2O4/reduced graphene oxide composites via layer-by-layer heteroassembly for high-performance supercapacitors

A novel binary composite consisting of CuCo2O4 nanocrystals and reduced graphene oxide is synthesized via a self-assembly approach combined with subsequent annealing. Cu-Co layered double hydroxides and graphite oxide are firstly exfoliated to charged monomolecular nanosheets. Controlled assembly between positively charged Cu-Co layered double hydroxides nanosheets and negatively charged graphene oxide affords the formation of sandwich-like precursor. After subsequent annealing, Cu-Co layered double hydroxides in the precursor is transformed into CuCo2O4 nanoparticles, while graphene oxide is reduced into reduced graphene oxide simultaneously. The channel architecture formed between CuCo2O4 nanoparticles and alternating reduced graphene oxide nanosheets provides a fast diffusion access for reaction species. The resultant composite delivers an initial specific capacitance of 291 F g(-1) (or 40.4 mA h g(-1)) with potential ranging from 0.05 V to 0.55 V at 1Ag(-1). In Particular, the specific capacitance of the composite reaches 389 F g(-1) (or 54 mA h g(-1)) at 1200th cycle and maintains no decay after extending to 5600 cycles. CuCo2O4 in the composite achieves a high specific capacitance of 978 F g(-1) (or 136 mA h g(-1)) at 3Ag(-1) if the weight percentage of components is corrected. In addition, the crucial influence of microstructures of the composite on its capacitive behaviors is deeply investigated by corresponding characterizations.