A comparative study on the effect of pH values and carbonic additives on the supercapacitive performance of LDH-derived Ni-Co-Al oxide

Abstract

The superb electrochemical properties of layered double hydroxides (LDHs) have not been properly investigated. High performance LDH-derived Ni-Co-Al oxide (NCL) has been proposed as a promising material for cathodic electrodes in supercapacitors. In this paper, a facile hydrothermal method was used to fabricate NCL electrodes at different pH values. LDH-derived Ni-Co-Al oxide nano-sheets were divergently grown at pH = 5.6. Then, composite electrodes with different amounts of graphene and carbon nano tube (CNT) were also synthesized. According to the results, the sample fabricated at pH = 8.6 (NCL3) showed the high capacitance of 1119.9 F g−1 at the high current density of 8 A g−1 and the capacitance retention of 89.2% after 2000 cycles. Moreover, its performance was compared with an NCL electrode containing 10 wt% CNT (NCLC). The effect of pH rate control on NCL electrodes and the effect of carbonic additives on the composite ones were examined by field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), Brunauer–Emmett–Teller (BET), thermogravimetric analysis (TGA), and electrochemical techniques. NCL3 (pH = 8.6) exhibited better capacitance stability at higher current densities up to 15 A g−1. Consequently, to improve high electrochemical properties, adjusting the pH value can be a suitable option in comparison with adding carbonic materials.