A new method for one-step hydrothermal synthesis of nickel cobalt selenide electrode material for supercapacitor

In this work, nickel cobalt selenide (NiCoSe 2 ) electrode material was successfully prepared on nickel foam by one-step hydrothermal method using cetyltrimethylammonium bromide as surfactant and ascorbic acid (AA) as reducing agent. Characterization measurement shows that selenium ion was reduced because of the addition of AA, and NiCoSe 2 was successfully prepared when the amount of AA increased to a certain level. When the dosage of AA was 2 mmol, small-grained NiCoSe 2 electrode was obtained, which exhibits a relatively high areal capacitance of 1600.7 mF cm −2 at a current density of 2 mA cm −2 in three-electrode system, and correspondingly, the inherent resistance and transfer resistance are 0.9502 Ω and 1.314 Ω, respectively. Furthermore, an asymmetric supercapacitor was constructed on the basis of prepared NiCoSe 2 and activated carbon to discuss the performance in practical application. It shows a high energy density of 0.116 mWh cm −2 and a power density of 1.619 mW cm −2 , as well as long cyclic stability of 83.7% after 4000 cycles. Further increase of AA may result in the change of microstructure of NiCoSe 2 from small grains to fiber, with a great deterioration in the electrochemical properties.