Improving the specific capacitance of Ni(OH)2-based supercapacitors by tailoring its porous structures and particle size

•A higher specific capacitance of Ni(OH)2-based supercapacitors.•Structure-directing reagents (PAM, CTMAB) were added in the hydrothermal synthesis of Ni(OH)2.•Its porous structures and particle size have been tailored.•The specific capacitance has been improved from 113 to 1200 F g−1.

Ni(OH)2 samples were synthesized by hydrothermal process, accompanied with poly(acrylamide) (PAM) or cetyltrimethylammonium bromide (CTMAB) as structure-directing reagents. Under the effects of PAM and CTMAB, both of the Ni(OH)2 samples show wider pore size distribution, especially more mesopores. Besides, Ni(OH)2-PAM presents fluffy wadding, and Ni(OH)2-CTMAB looks like pompon sphere. The Ni(OH)2-PAM and Ni(OH)2-CTMAB based electrodes have a specific capacitance of 1200 and 757 F g−1, respectively at the discharge current density of 1 A g−1, much higher than that of Ni(OH)2 with no structure-directing reagent (only 113 F g−1). Therefore, appropriate structure-directing reagents are necessary to improve the electrochemical performance of electrode materials.