Preparation of microalgae-based carbon materials with Ni(OH)2 doping and their electrochemical performance

Supercapacitors are a new type of energy storage devices with many advantages. In this study a novel composite material named NiC were synthesized to improved their electrochemical performance in supercapacitors. It was composite of Ni(OH)2 and microalgae-based N-doped activated carbon materials. Activated carbon material prepared from defatted microalgae was excellent electrode material because of their nitrogen-rich characterization and porous structure. The Ni(OH)2 as a metallic material could provide considerable pseudo-capacitance for capacitors. In this study, Ni(OH)2 was successfully doped into carbon materials using a hydrothermal method at a temperature of 150 °C for 4 h. The flower-like structure of metallic materials was observed in SEM images and two forms of elemental Ni ions (Ni3+ and Ni2+) were detected in XPS. The porosity of the composite materials NiC was retained to some extent (specific surface area of 502 m2/g for sample NiC10). Moreover, the specific capacitance value of composite material NiC20 was increased by 190 % compared to its parent carbon material, indicating that the capacitive performance of the composite materials was significantly improved. The capacitance retention of NiC20//NiC20 in a two-electrode system was up to 75.29 % over 5000 cycles. This research will provide necessary information for high-performance electrochemical materials based on microalgae-based carbon materials. [Display omitted] •Microalgae based N-doped activated carbons were obtained by pyrolysis and activation.•Composite of Ni(OH)2 and activated carbon was synthesized by hydrothermal method.•Composite materials NiC presented high specific capacitance.•Excellent electrochemical properties of composite materials were obtained.