Scalable Synthesis of Triple-Core–Shell Nanostructures of TiO₂@MnO₂@C for High Performance Supercapacitors Using Structure-Guided Combustion Waves

Core–shell nanostructures of metal oxides and carbon-based materials have emerged as outstanding electrode materials for supercapacitors and batteries. However, their synthesis requires complex procedures that incur high costs and long processing times. Herein, a new route is proposed for synthesizing triple-core–shell nanoparticles of TiO₂@MnO₂@C using structure-guided combustion waves (SGCWs), which originate from incomplete combustion inside chemical-fuel-wrapped nanostructures, and their application in supercapacitor electrodes. SGCWs transform TiO₂ to TiO₂@C and TiO₂@MnO₂ to TiO₂@MnO₂@C via the incompletely combusted carbonaceous fuels under an open-air atmosphere, in seconds. The synthesized carbon layers act as templates for MnO₂ shells in TiO₂@C and organic shells of TiO₂@MnO₂@C. The TiO₂@MnO₂@C-based electrodes exhibit a greater specific capacitance (488 F g⁻¹ at 5 mV s⁻¹) and capacitance retention (97.4% after 10 000 cycles at 1.0 V s⁻¹), while the absence of MnO₂ and carbon shells reveals a severe degradation in the specific capacitance and capacitance retention. Because the core-TiO₂ nanoparticles and carbon shell prevent the deformation of the inner and outer sides of the MnO₂ shell, the nanostructures of the TiO₂@MnO₂@C are preserved despite the long-term cycling, giving the superior performance. This SGCW-driven fabrication enables the scalable synthesis of multiple-core–shell structures applicable to diverse electrochemical applications.