1. Schematic illustration for the two-step preparation process of MnO₂ hollow polyhedrons nanostructures assembled on carbon cloth^[13]

2. SEM images of nanostructured MnO₂ fabricated by using Sol-Gel and template methods with (a) AAO template A and (b) AAO template B^[23]

3. (a) FESEM, (b, c) TEM and (d) HRTEM images of MnO₂ assembled nanosheets with inset in (d) showing the corresponding SAED pattern ^[28]

4. Capacitance retention of δ-MnO₂ at current density of 2.1 A/g in 1 mol/L Na₂SO₄ electrolyte with inset showing the corresponding charge-discharge curves^[16]

5. UV-Vis transmittance spectra of (a) PANI, (b) MnO₂, and (c) PANI/MnO₂ at different potentials with insets in (c) showing the photos of PANI/MnO₂ hybrid film electrodeposited on ITO/glass at bleached (upper, light greenish yellow) and colored state (lower, dark bluish green), and (d) switching curves comparison between PANI, MnO₂, and PANI/MnO₂ hybrid films at λ_{680 nm} (-0.4 V/+0.4 V, 60 s/cycle)^[47]

6. (a) SEM images of rod-like α-MnO₂, wire-like α-MnO₂, tube-like α-MnO₂, and flower-like Mn₂O₃; (b) Toluene conversion as a function of reaction temperature over the catalysts under the conditions of a toluene concentration of 10^-3, toluene/ O₂ = 1/400 (mol/mol), and a space velocity of 20000 mL/(g⋅h)^[51]

7. Measurement of FP following the addition of various concentrations of Ag⁺ in the presence of MnO₂ nanosheets (80 μg/mL) with inset showing the linear relationship between ΔFP and Ag⁺ concentration^[52]