Growth of Ni3Se2 nanosheets on Ni foam for asymmetric supercapacitors

We present a facile one-step hydrothermal method to in situ grow nickel selenide (Ni3Se2) nanosheets on nickel (Ni) foam (Ni3Se2/Ni) by using SeO2 as selenide source, Ni foam as nickel source and NaBH4 as reducing agent. The mole ratio of NaBH4/SeO2 is optimized as 4:1. An asymmetric supercapacitor (ASC) is fabricated by using as synthesized Ni3Se2/Ni as positive electrode and activated carbon (AC) as negative electrode. The synthesized materials and assembled devices are measured and characterized by a field emission scanning electron microscopy, powder X-ray diffraction, cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The results shows that the as-synthesized Ni3Se2/Ni electrode possesses a high specific capacitance of 854 F g(-1) at 1 A g(-1). The ASC can steadily operate with a high voltage of 1.6 V in 3 M KOH electrolytes, and possesses a superior energy density of 23.3 W h kg(-1) at a power density of 398.1 W kg(-1). In addition, the Ni3Se2//AC ASC shows excellent charge/discharge stability, after 5000 cycles the capacitance retention reaches 91.11%. The excellent performance of Ni3Se2/Ni electrode is mainly due to the pseudo-capacitive by Ni3Se2 and the 3D structure of Ni foam.