Surfactant-Free Synthesis of Nb2O5 Nanoparticles Anchored Graphene Nanocomposites with Enhanced Electrochemical Performance for Supercapacitor Electrodes.

Nb2O5/graphene nanocomposites without any surfactant are synthesized by an in situ microwave irradiation technique. Structural and morphological studies revealed that the prepared composites were composed of Nb2O5 nanoparticles intercalated into the graphene sheet. The thermal stability of graphene oxide, Nb2O5, and Nb2O5/graphene nanocomposite was studied by the TGA. The electrochemical properties are assessed by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy analyses. The specific capacitance of Nb2O5/graphene nanocomposites is greater (633 Fg-1) than pure Nb2O5 nanoparticles (221 Fg-1) and graphene (290 Fg-1) at a current density of 1 Ag-1. The long-term cyclic measurement confirms higher cyclic stability of the nanocomposite with capacitance retention of 99.3% after 5000 cycles without performance degradation. The composites exhibit higher electrochemical conductivity and allow effective ions and charge transport over the entire electrode surface with aqueous electrolyte. The electrochemical study suggests that Nb2O5/graphene nanocomposites have the potential to be an effective electrode for superior performance supercapacitor applications.

Enhanced electrochemical performance of α-MoO3/graphene nanocomposites prepared by an in situ microwave irradiation technique for energy storage applications.

Nanoparticles of α-molybdenum oxide (α-MoO3) are directly grown on graphene sheets using a surfactant-free facile one step ultrafast in situ microwave irradiation method. The prepared α-MoO3 and α-MoO3/G nanocomposites are analysed by different characterization techniques to study their structural, morphological and optical properties. Transmission electron microscope images reveal the intercalation of three dimensional (3D) α-MoO3 nanoparticles into 2D graphene sheets without any agglomeration. The electrochemical results exhibit improved performance for the α-MoO3/G composite electrode compared to pristine α-MoO3 owing to its structural superiority. The specific capacitance (C s) values of the α-MoO3/G composite and pristine α-MoO3 are measured to be 483 and 142 F g-1 respectively at a current density of 1 A g-1. The α-MoO3/G composite maintains a very strong cyclic performance after 5000 cycles. The capacitance retention of the composite electrode shows stable behavior without any degradation confirming its suitability as an enduring electrode material for high-performance supercapacitor applications.

Freestanding flexible, pure and composite form of reduced graphene oxide paper for ammonia vapor sensing.

Metal oxides based graphene nanocomposites were used for ammonia vapour sensing. The self-assembly process was adopted to prepare freestanding flexible pure rGO, CeO2-rGO and SnO2-rGO composite papers. The structural studies confirmed the formation of rGO composite papers. The ammonia vapor sensing was demonstrated using an impedance analyzer at different humidity levels as well as concentration. The CeO2-rGO composite paper achieved a sensitivity of 51.70 ± 1.2%, which was higher than that of pure rGO and SnO2-rGO composite paper. Both the surfaces (top and bottom) of the papers are active in efficiently sensing ammonia, which makes the present work unique. The results reveal that metal oxide/rGO papers can be effectively utilized in real time sensor application.