KOH-mediated controllable synthesis of NiSe/Ni3Se2 composites for high-performance supercapacitors

Constructing multiphase composites is an effective approach to optimizing the performance of electrode materials. This work innovatively proposes a facile synthesis method that utilizes nickel foam solely as both the current collector and nickel source, eliminating the need for additional nickel sources. Through a one-step, highly efficient hydrothermal selenization process, a NiSe/Ni 3 Se 2 composite through with the same elemental composition is successfully constructed on the surface of nickel foam. The uniqueness of this method lies in the precise control of the composition ratio and morphology of NiSe and Ni 3 Se 2 components by meticulously adjusting the concentration of KOH in the hydrothermal system. The resulting material comprises solely Se and Ni, highlighting a high degree of chemical purity and structural tunability. The obtained NiSe/Ni 3 Se 2 composite exhibits a remarkable specific capacitance of 13.2 F cm −2 at a current density of 5 mA cm −2 , with a capacitance retention rate of 90 % after 10,000 cycles. When the NiSe/Ni 3 Se 2 composite electrode is assembled into an asymmetric supercapacitor (ASC) with activated carbon as the negative electrode, it demonstrates a high specific capacitance of 4.96 F cm −2 at a current density of 5 mA cm −2 . After 10,000 cycles, the capacitance retention rate remains as high as 99.3 %. This work not only enriches the synthesis strategies for composite with the same elemental composition but also provides new insights and material foundations for the design and development of high-performance supercapacitors, portending broad application prospects for such materials in the field of energy storage. • Preparation of NiSe/Ni 3 Se 2 composites by one-step hydrothermal method. • KOH concentration controls the composition and morphology of NiSe/Ni 3 Se 2 . • NiSe/Ni 3 Se 2 electrode exhibits specific capacitance of 13.2 F cm −2 at 5 mA cm −2 .