Search

In recent times, transition-metal oxides have been recognized as highly promising candidates for supercapacitor applications. Nevertheless, their progress in diverse fields has been hindered by challenges such as poor electrical conductivity and a shortage of active reaction centers. Doping heteroatoms would overcome these drawbacks and enhance the supercapacitor properties in transition metal oxides. Herein, the phosphorous-doped 2D nanosheet assembled 3D Mn2V2O7micro flowers were grown on the Nickel foam using the hydrothermal method and successively phosphatized in a tube furnace, which was utilized as a binder-free supercapacitor electrode. The synthesis process involved varying the concentration of phosphorus (P), resulting in the successful formation of uniform P-decorated Mn2V2O7microflowers. The unique microflower structure and doping P into the Mn2V2O7material enhance the electrochemical properties with a specific capacity of 850C g−1(1545 F g−1) at 1 A g−1in a three-electrode cell. Moreover, the assembled Mn2V2O7–600/NF//AC device delivers a specific capacity of 258C g−1(211 F g−1) at 1 A g−1with a remarkable rate of 47 % at a high current density of 20 Ag −1. The device achieved a maximum energy density of 43.2 Wh kg−1at a power density of 604.7 W kg−1, and it maintained 91 % of initial capacity after 10,000 charge/discharge cycles at 20 A g−1. These results suggest that the P-doping 2D nanosheet assembled 3D Mn2V2O7could be promising electrode materials for supercapacitor applications.

Recent advances in using biological scaffolds for nanoparticle synthesis have proven to be useful for preparing various nanostructures with uniform shape and size. Proteins are significant scaffolds for generating various nanostructures partly because of the presence of many functional groups to recognize different chemistries. In this endeavor, cocosin protein, an 11S allergen, is prepared from coconut fruit and employed as a potential scaffold for synthesizing Mn3O4materials. The interaction between protein and manganese ions is studied in detail through isothermal calorimetric titration. At increased scaffold availability, the Mn3O4material adopts the exact hexamer structure of the cocosin protein. The electrochemical supercapacitive properties of the cocosin–Mn3O4material are found to have a high specific capacitance of 751.3 F g–1at 1 A g–1with cyclic stability (92% of capacitance retention after 5000 CV cycles) in a three-electrode configuration. The Mn3O4//Mn3O4symmetric supercapacitor device delivers a specific capacitance of 203.8 F g–1at 1 A g–1and an outstanding energy and power density of 91.7 W h kg–1and 899.5 W kg–1, respectively. These results show that cocosin–Mn3O4could be considered a suitable electrode for energy storage applications. Moreover, the cocosin protein to be utilized as a novel scaffold in protein–nanomaterial chemistry could be useful for protein-assisted inorganic nanostructure synthesis in the future.

The spinel structured materials (e.g., MnCo2O4.5) are good aspirants for supercapacitor electrode application due to their outstanding pseudocapacitor performance. However, due to the collapsing of the crystal and morphological structures during electrochemical analysis, inferior cyclic stability and low energy density problems are inevitable when the materials are used as supercapacitor electrodes. Alteration of intrinsic (diffusion-controlled) to extrinsic (surface-controlled) capacitive behavior is the effective solution to overcome these issues. Herein, the intrinsic capacitor behavior of the MnCo2O4.5material was altered into an extrinsic mechanism through the precipitation process with the aid of a deoxyribonucleic acid (DNA)-based structural engineering process. The MnCo2O4.5coated on nickel foam current collector delivered the specific capacity of 649C g−1at 1 A g−1and retained 97 % of its initial capacity after 5000 cycles at 20 A g−1in three-electrode configurations. Additionally, the MnCo2O4.5//Activated carbon asymmetric device showed a specific capacity of 93.8C g−1at 1 A g−1with energy and power densities of 33.4 Wh Kg−1and 681 W Kg−1at 1 A g−1, respectively. DNA-based structural engineering demonstrates the tuning of intrinsic to extrinsic capacitive behavior resulting in better supercapacitor properties in MnCo2O4.5material.

Mixed transition-metal oxides (MTMOs) are attracting tremendous attention as a battery-type electrode due to their high electrical conductivity and structural stability. However, utilizing these electrodes in practical applications is hindered by capacity degradation, especially during the long-term cycle. These limitations could be overcome by constructing electrodes by introducing the carbonaceous material into the MTMO matrix. Accordingly, in this work, a facile hydrothermal method is employed to develop nitrogen-doped carbon dots (NCDs)-integrated bismuth molybdenum oxide (Bi2MoO6; BMO) (NCD/BMO) composites, where the concentration of NCDs is varied, such as 2, 5, 10, and 15 wt %. The structural and chemical state analyses of the samples confirm the formation of the orthorhombic BMO system and the chemically integrated NCD/BMO composites. The morphology analysis revealed a brick-like structure for bare-BMO with an average size of ∼100 nm and a rod-like morphology for the NCD/BMO composites, which is attributed to the interaction of NCDs with growing BMO particles leading to the rod-like formation of the resultant composites. The electrochemical performance of the developed materials is studied in a three-electrode and symmetric assembly system. Among the composites, the 10 wt % NCD/BMO (BMO–C10) composite exhibited an enhanced specific capacity of 561 C g–1(155.8 mA h g–1) at a current density of 1 A g–1in 6 M KOH electrolyte. Besides, the assembled symmetric device achieved an energy density and a power density of 44.2 W h kg–1and 720 W kg–1, respectively, at a current density of 1 A g–1. In addition, the assembled symmetric device maintained excellent cyclic stability of ∼87.3% up to 10,000 cycles at 20 A g–1current density. The obtained results demonstrate that the NCD/BMO composite could be an efficient battery-type electrode material for promising supercapacitor applications.