CTAB-assisted synthesis of porous cuboid NiCo2O4 powders for high-performance supercapacitor

NiCo2O4 powders with columnar-, rod-, porous cuboid-, and octahedral-like morphologies were prepared by hydrothermally treatment of oxalate precipitates in the presence of various amounts of cetyltrimethylammonium bromide (CTAB) surfactant. The structural, microstructural, and electrochemical properties of NiCo2O4 powders were characterized by X-ray diffractometry, scanning electron microscopy, cyclic voltammetry, and galvanostatic charge/discharge techniques. Because of agglomeration of NiCo2O4 nanoparticles, the specific surface areas decreased from 36.3 to 14 m(2) g(-1) with CTAB content. The porous cuboid-like NiCo2O4 powders showed the highest specific capacitance of 1353 F g(-1) at 1 A g(-1), decreasing to 1021 F g(-1) at 10 A g(-1). The analyzed contribution of various storage mechanisms showed that a mixture of capacitive and diffusion-controlled processes was necessary for obtaining the highest specific capacitance. The porous cuboid-like NiCo2O4 powders// activated carbon hybrid capacitor showed the comparable performance of electrochemical energy storage, including energy density of 23.3 Wh kg(-1) at power density of 1398 W kg(-1).