Honeycomb-like open-edged reduced-graphene-oxide-enclosed transition metal oxides (NiO/Co3O4) as improved electrode materials for high-performance supercapacitor

Abstract

• Honeycomb reduced graphene oxide (HOrGO) serves as an efficient conductive network. • The HOrGO/TMOs (NiO/Co 3 O 4 ) hybrids were synthesized via microwave-assisted method. • The micron-sized (~100 μm) open edges of HOrGO NSs hold the NiO/Co 3 O 4 nanoparticles. • The HOrGO/TMOs hybrids deliver specific capacitance 910 F/g at scan rate 20 mV/s. • The HOrGO/TMOs hybrids exhibited high retention with stabile performance. Honeycomb-like open edges reduced graphene oxide nanosheets (HOrGO NSs) filled with transition metal oxides (TMOs) as NiO/Co 3 O 4 nanoparticles (NPs) has been synthesized by a simple and cost-effective microwave irradiation method. The microwave irradiation assisted synthesized HOrGO filled with NiO/Co 3 O 4 NPs (HOrGO/TMOs) hybrids exhibits high specific capacitance with improved cycling stability as excellent electrode materials for supercapacitors (SCs). The HOrGO NSs contains high surface area (~570 m 2 g −1 ) due to highly exfoliated nanostructure comprising open edges enriched morphology. In HOrGO/TMOs hybrids, the several micron-sized (~100 μm) open edges of HOrGO NSs holds the NiO/Co 3 O 4 NPs with finely separated thin few-layer graphene NSs. The structural/ morphological analysis of synthesized HOrGO NSs and HOrGO/TMOs hybrids were extensively characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Raman spectra, thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET) surface area. The HOrGO/TMOs hybrids deliver high specific capacitance of 910 F g −1 and high robust cycling stability with capacitance retention as 89.9% after continuous 2000 cycles. The proposed mechanism explain the microwave irradiation assisted formation of HOrGO/TMOs hybrids and provides a general and low-cost approach to synthesized high quality graphene hybrids materials for SCs application.