Direct formation of porous MnO2/Ni composite foam applied for high-performance supercapacitors at mild conditions

Here, a novel three dimensional Ni foam-supported porous MnO2 film (porous MnO2/Ni composite foam) was successfully synthesized by the simple hydrothermal method using Ni foam as substrate. The porous MnO2 film had closely coated on the backbones of the Ni foam without assistant of surfactant at mild conditions. At the same time, the pore size of porous MnO2/Ni composite foam was easily controlled by the reaction temperature. Furthermore, it was found that the capacitive properties of porous MnO2/Ni composite foam were related to the pore size of MnO2 film. It showed smaller pore size, and it exhibited better capacitive behavior for the electrode, in which the porous MnO2/Ni composite foam with pore size of ca.50.0∼150.0 nm showed high rate capability of 1086.0 F/g at 10.0 A/g and good cycle stability with capacitance retention of 98.0% after 500 cycles. The high capacitive properties was due to the active materials MnO2 grown on the the backbone of the Ni foam and porous structure of MnO2 materials, resulting in the reduce of resistance and enhancement of active surface area. Our work not only demonstrates the controlled synthesis of high-quality porous MnO2/Ni composite foam at mild conditions on a large scale, but also provides a universal route for the rational design of supercapacitors with high performance.