Self-assembled hierarchical porous layered double hydroxides by solvothermal method and their application for capacitors

In this paper, for the first time, Ni/Al layered double hydroxides (LDHs) with high specific surface area and high porosity were developed via a facile and environmentally friendly solvothermal approach. The obtained Ni/Al LDHs have a diameter of 1-10 μm, which are self-assembled by 15 nm-sized primary particles and 200 nm size secondary particles. The BET surface area of the sample is determined to about 300 m² g⁻¹, which is about three times than that prepared by conventional hydrothermal route. The average pore size is 3.97 nm. Notedly, the specific capacitance of this hierarchical porous Ni/Al LDHs reaches 477 F g⁻¹ at a current density of 2.5 A g⁻¹, which is nearly double that of Ni/Al LDHs synthesized by conventional hydrothermal procedure. The capacitance loss is less than 5% after 400 charge-discharge cycles, suggesting the high potential as electrode materials in electrochemical capacitors. The formation mechanism of self-assembled hierarchical porous Ni/Al LDHs through solvothermal method was also proposed.