Oxygen-defect-rich 3D porous cobalt-gallium layered double hydroxide for high-performance supercapacitor application

In this work, oxygen-defect-rich, three-dimensional (3D) cobalt-gallium layered double hydroxides (Co_0.50-Ga_0.50-LDH) assembled by porous and ultrathin nanosheets are prepared by a simple one-step strategy. Briefly, an aqueous solution containing Co²⁺ and Ga³⁺ is quickly pouring into the aqueous solution of hexamethylenetetramine, the state-of-the-art LDH was obtained followed by a mild and fast hydrothermal reaction. This mild and rapid synthesis strategy introduces a large number of pores into the ultrathin LDH nanosheets, resulting in a high concentration of oxygen vacancies in the Co_0.50-Ga_0.50-LDH, and the concentration of oxygen vacancies can be arbitrarily modulated, which has been corroborated by X-ray photoelectron spectroscopy and electron spin resonance measurements. The synergistic effect of the oxygen vacancy and the introduced Ga ions in the LDH nanosheets enhances the adsorption of the LDH nanosheets on OH^-, endowing Co_0.50-Ga_0.50-LDH with outstanding performance for the supercapacitor application. Co_0.50-Ga_0.50-LDH offers a high specific capacity (0.62C·cm^-2) at 10 mV·s^-1 and extraordinary cycling stability. An aqueous asymmetric supercapacitor (ASC) constructed with Co_0.50-Ga_0.50-LDH and activated carbon (AC) materials exhibits high energy density and a long lifespan. This result encourages the wide application of porous ultrathin LDH nanosheets in energy storage, catalysis and light response.