Fabrication of ternary NiCoMoOx with yolk-shell hollow structure as a positive electrode material for high-performance electrochemical capacitor applications.

Although the fabrication of hollow nanostructures from single and binary transition metal oxides has been accomplished effectively, there still exists a significant challenge in creating advanced hollow morphologies comprising mixed transition metal oxides such as ternary and quaternary compositions. In this context, we have adopted an alternative approach by employing a straightforward self-templating method to synthesize ternary metal molybdate nanomaterials. These materials possess the chemical composition of NiCoMoOx and exhibit a unique nanoporous yolk-shell hollow structure. Commencing with mixed metal-glycerate solid spheres, we have successfully guided the formation of this chemical composition and distinctive yolk-shell hollow sphere architecture through meticulous thermal treatment control. The consistency of our results is confirmed through SEM images. Thanks to their robust structural integrity, advanced internal morphology, and increased surface area, these hierarchical hollow spheres demonstrate remarkable electrochemical performance when utilized as advanced electrode materials for supercapacitors. When serving as electrode materials in supercapacitors, these nanoporous NiCoMoOx yolk-shell hollow spheres deliver a specific capacitance of 1125 F g-1 at a current density of 0.5 A g-1, maintaining an impressive cycling stability of 91.48% even after 5000 cycles. In a hybrid device configuration wherein activated carbon (AC) functions as the negative electrode and NiCoMoOx yolk-shell hollow spheres serve as the positive electrode, exceptional performance is observed. This configuration achieves a substantial specific energy density of 44.67 W h kg-1, alongside a maximum power density of 8000 W kg-1, and exceptional cycling stability of 93.03% even after 5000 cycles.

Natural sensitizer extracted from Mussaenda erythrophylla for dye-sensitized solar cell.

In this study, a natural dye from the flowers of Mussaenda erythrophylla extracted separately in ethanol and de-ionized water was employed as a photosensitizer in DSSCs. The quantitative phytochemical analyses were performed on both extracts. The existence of flavonoids (anthocyanin) and chlorophyll a pigments in the ethanol extract of the dye was confirmed by the UV-Visible spectroscopy. The stability study performed on the said ethanol extract confirmed that the dye extracted in ethanol was stable in the dark and did not degrade for nearly 50 days. The presence of the dye molecules and uniform adsorption of them on the P25-TiO2 surface were confirmed by fourier transform infrared spectroscopy and atomic force microscopy, respectively. Moreover, the influence of dye concentration and pH on the optical properties of the dye was also studied. The natural dye extracted in ethanol was employed in DSSCs, fabricated by utilizing the said dye sensitized P25-TiO2 photoanodes, [Formula: see text]/[Formula: see text] electrolyte, and Pt counter electrode. Photovoltaic performances of the fabricated devices were determined under simulated irradiation with the intensity of 100 mWcm-2 using AM 1.5 filter. The device fabricated with the P25-TiO2 photoanode sensitized by the dye extracted in ethanol at pH = 5 exhibited the best power conversion efficiency (PCE) of 0.41% with the JSC of 0.98 mAcm-2 which could be attributed to the optimum light absorption in the visible region of solar spectrum by the chlorophyll a and anthocyanin molecules in the extracted natural dye.

Hierarchical Cube-in-Cube Cobalt-Molybdenum Phosphide Hollow Nanoboxes Derived from the MOF Template Strategy for High-Performance Supercapacitors.

The design of hierarchical hollow nanostructures with complex shell architectures is an attractive and effective way to obtain a desirable electrode material for energy storage application. Herein, we report an effective metal-organic framework (MOF) template-engaged method to synthesize novel double-shelled hollow nanoboxes, in terms of chemical composition and structure complexity, for supercapacitor application. Starting from cobalt-based zeolitic imidazolate framework (ZIF-67(Co)) nanoboxes as the removal template, we developed a rational preparation approach to synthesize cobalt-molybdenum-phosphide (CoMoP) double-shelled hollow nanoboxes (donated as CoMoP-DSHNBs) through (i) ion-exchange reaction, (ii) template etching, and (iii) phosphorization treatment, respectively. Notably, despite the previously reported works, the phosphorization was simply done using the facile solvothermal method, without employing annealing and high-temperature conditions, which can be considered as one of the merits of the current work. CoMoP-DSHNBs showed excellent electrochemical properties owing to their unique morphology, high surface area, and optimal elemental composition. In a three-electrode system, the target material showed a superior specific capacity of 1204 F g-1 at 1 A g-1 with a remarkable cycle stability of 87% after 20000 cycles. The hybrid device formed of activated carbon (AC) as the negative electrode and CoMoP-DSHNBs as the positive electrode exhibited a high specific energy density of 49.99 W h kg-1 and a maximum power density of 7539.41 W kg-1 with a great cycling stability of 84.5% after 20,000 cycles.