Fabrication of ternary NiCoMoO _x 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 NiCoMoO_x 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 NiCoMoO_x 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 NiCoMoO_x 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.