Hydrothermally synthesized nickel cobalt layered double hydroxide for efficient oxygen evolution reaction and supercapacitor applications

Abstract

As fossil fuels deplete and the global population grows, the demand for multifunctional materials has increased significantly. Electrode materials based on nickel (Ni) and cobalt (Co) have attracted considerable attention as multifunctional materials due to their abundance in the Earth's crust, cost-effectiveness, and environmentally friendly properties. Herein, we have synthesized nickel cobalt layered double hydroxide (NiCo LDH) thin film on nickel foam (NF) via a facile one-step hydrothermal method at different reaction times of 4, 8 and 12 h. The NiCo LDH thin films synthesized at 120 °C for 12 h exhibited a highest specific capacitance of 1454 F/g at a current rate of 2 mA/cm² in 1 M KOH electrolyte. It also showed capacitance retention of 62 % after 1000 charge-discharge cycles. Moreover, in case of oxygen evolution reaction (OER) activity, the overpotentials of electrodes fabricated at 8 and 12 h are very close (259 mV and 280 mV, iR corrected) at low current density (10 mA/cm²) whereas it is deviated at higher current range. Thus, the lower Tafel slope of 23 mV/dec of the NiCo LDH fabricated at 12 h is superior to that of the electrode fabricated at 8 h (38 mV/dec) suggesting faster reaction kinetics. It has excellent electrochemical stability of 30 h in alkaline electrolyte without much deviation of overpotential. This result suggests that NiCo LDH can serve as a potential candidate as a multifunctional electrode material for devices like supercapacitors and water electrolyzers.