Table 1.

Preparation of MnO₂ Nanomaterials

Methods		Preparation details	Advantages	Disadvantages
Chemical precipitation		The metal salts dissolved in aqueous solution are converted into insoluble compounds or hydrated oxides by adjusting the reaction conditions, and then precipitated out, and nanomaterials are obtained after further treatment.	Low reaction temperature, simple operation and low cost	Poor homogeneity, agglomerative
Template method	Flexible template method	Use surfactants, flexible organic molecules and block polymers to form micellar templates with different morphologies, and utilize the effects of electrostatic forces, hydrogen bonding and van der Waals forces to obtain nanomaterials with different morphologies.	Simple and inexpensive	Difficult for uniformity and size, difficult to remove surfactants
	Rigid template method	Manganese dioxide nanomaterials are obtained by using polymers such as silica, carbon nanotubes and polystyrene as templates, and manganese dioxide is grown on their surfaces.	High stability and easy for uniformity and size	High production cost and low efficiency
Hydrothermal method		The preparation method of generating specific products by reacting between reactants under the pressure of a solution with water as solvent under closed conditions at a certain temperature.	High purity, good dispersion, complete crystal shape and controllable grain size	Dangerous for high temperature and pressure
Sol-gel method		Synthesis method to hydrolyze and condense metal-alcohol salts or inorganic salts and gradually turn them into gels, and then obtain powder materials after corresponding treatment	Uniform dispersion of chemical scale and high purity	Long reaction cycles and agglomeration during calcination
Solid phase synthesis		The synthesis method of generating manganese dioxide NPs by solidification reaction at lower temperature, the reaction process is mainly through the solid reactants high-speed ball milling.	Simple experimental method, less environmental pollution, high yield of products, good reaction selectivity	Not suitable for single-crystal nanoscale products