Reduced graphene oxide (rGO): supported NiO, Co3O4 and NiCo2O4 hybrid composite on carbon cloth (CC)-bi-functional electrode/catalyst for energy storage and conversion devices

In the present work, we have synthesized a series of composites with NiO, Co3O4, and NiCo2O4 and reduced graphene oxide (RGO). The hybrid composites were fabricated trough a single step hydrothermal approach with subsequent heat treatment. X-ray diffraction, Raman spectroscopy and Transmission Electron Microscopy analyses indicate the metal oxide nanoparticles were integrated well in the carbon cloth substrate with rGO support. The as-prepared materials were evaluated as the electrodes for energy storage and conversion devices. As the electrode for supercapatteries, rGO supported NiCo2O4 exhibits highest specific capacity of 333 C g(-1) at a specific current of 1 mA cm(-1) when compared to their monometallic oxides and also exhibits excellent cycling stability with 89% retention at 5 mA cm(-1) after 5000 cycles in a three-electrode system. Furthermore, we have investigated the electro-oxidation of methanol with these electrode in an alkaline medium. Compared to individual oxide composites, the NiCo2O4-rGO electrode shows excellent electro-catalytic activity towards methanol oxidation with low onset potential of similar to 0.3 V and high catalytic current density. The observed bi-functionality of rGO supported metal oxide composite could be attributed to the enhanced electrical conductivity and the well-integrated contact with carbon cloth back bone. Thereby it can be concluded that the design of hybrid composite electrode could be the better choice of electro-active materials for both energy storage and conversion applications.