Mesoporous Quaternary Ce-Ni-Mn-Co Oxides as Electrodematerials forHighPerformance Flexible Solid-StateAsymmetric Supercapacitors

Enhanced electrochemical performance of MnNi2O4/rGO nanocomposite as pseudocapacitor electrode material and methanol electro-oxidation catalyst

Binary transition metal oxides with encouraging electrocatalyst properties have been suggested as electrode materials for supercapacitors and methanol oxidation. Hence, in this work, a binary mixed metal oxide based on nickel and manganese (MnNi₂O₄) and its hybrid with reduced graphene oxide were synthesized by a one-step hydrothermal method. After physical and morphological characterization, the potential of these nanostructures was investigated for use as supercapacitor electrodes and methanol electro-oxidation. The results of the electrochemical analysis showed a substantial effect of adding rGO to the MnNi₂O₄. The MnNi₂O₄/rGO hybrid electrode supercapacitor exhibited good stability of 93% after 2000 consecutive CV cycles and a specific capacitance of 575 F g^-1at the current density of 0.5 A g^-1. Furthermore, the application of this hybrid nanomaterial in the methanol electro-oxidation reaction (MOR) indicated its appropriate electrochemical efficiency and stability in methanol oxidation. Our results show that MnNi₂O₄/rGO can be considered as a promising electrode material for energy applications.

Boost of Charge Storage Performance of Graphene Nanowall Electrodes by Laser-Induced Crystallization of Metal Oxide Nanostructures

Major research efforts are being carried out for the technological advancement to an energetically sustainable society. However, for the full commercial integration of electrochemical energy storage devices, not only materials with higher performance should be designed and manufactured but also more competitive production techniques need to be developed. The laser processing technology is well extended at the industrial sector for the versatile and high throughput modification of a wide range of materials. In this work, a method based on laser processing is presented for the fabrication of hybrid electrodes composed of graphene nanowalls (GNWs) coated with different transition-metal oxide nanostructures for electrochemical capacitor (EC) applications. GNW/stainless steel electrodes grown by plasma enhanced chemical vapor deposition were decorated with metal oxide nanostructures by means of their laser surface processing while immersed in aqueous organometallic solutions. The pseudocapacitive nature of the laser-induced crystallized oxide materials prompted an increase of the GNW electrodes' capacitance by 3 orders of magnitude, up to ca. 28 F/cm³ at 10 mV/s, at both the positive and negative voltages. Finally, asymmetric aqueous and solid-state ECs revealed excellent stability upon tens of thousands of charge-discharge cycles.