Effects of pore diameters on the pseudocapacitive property of three-dimensionally ordered macroporous manganese oxide electrodes

► We report a facile synthesis of 1.8 ± 0.2-nm MnO2 nanoparticles. ► MnO2 nanoparticles used as precursors for producing highly-ordered porous pseudocapacitors. ► Porous pseudocapacitors exhibit ultrahigh capacitance (765 F/g) due to faster ion transportation. ► Pseudocapacitive behavior of the porous pseudocapacitors depends on their pore sizes. ► Smaller pore diameter provides higher specific capacitance.