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

Abstract

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.