Template free synthesis of vacancy tailored, highly mesoporous one-dimensional δ-MnO2 for energy storage applications

Abstract

This work involves the synthesis of highly conducting, ultra-thin, mesoporous manganese dioxide, nanotubes and nanowires, using a sol–gel technique. This is a template-free method for preparing mesoporous (3.3 to 5.4 nm) nanotubes and nanowires of 10–15 nm radius with surface area (221.19 m²/g-102.09 m²/g). In the MnO₂ lattice, oxygen and cationic vacancies are tailored by changing the reducing agent for improved energy storage. X-ray photoelectron spectroscopic studies are conducted to quantify the oxygen and cationic vacancies. The tailored one-dimensional δ-MnO₂ is used as an electrode material for symmetric and asymmetric supercapacitor designs. A non-toxic, less volatile aqueous neutral electrolyte is used for the supercapacitive measurement, giving a specific capacitance of 460.75 F g⁻¹ at 2 mV s⁻¹ with symmetric mode at 1 V. With activated carbon, this material can also produce asymmetric supercapacitors with a specific capacitance of 107.38 F g⁻¹ at 10 mV s⁻¹ at 1.7 V.