Design and construction of core-shell heterostructure of Ni-V layered double hydroxide composite electrode materials for high-performance hybrid supercapacitor and L-Tryptophan sensor

Layered double hydroxide (LDH) is considered as a potential electrode material for supercapacitors (SCs) due to its excellent theoretical capacitance. However, the conductivity of LDH is not particularly ideal. The reasonable design of new electrode materials with core-shell structure is an effective strategy to improve the electrochemical performance. Herein, we prepared NiCo2S4@NiV-LDH/NF composite material with a core-shell nanostructure through a simple hydrothermal method. In addition, NiCo2S4@NiV-LDH/NF-1, NiCo2S4@NiV-LDH/NF-2, NiCo2S4@NiV-LDH/NF-3 were synthesized by adjusting the sulfur concentration. Benefited from the synergistic reaction of each component, the optimized NiCo2S4@NiV-LDH/NF-2 composite material has excellent electrochemical performance. The specific capacity is 1778.8 C g−1 (3557.6 F g−1) at 1 A g−1. In addition, a typical hybrid supercapacitor device was assembled with NiCo2S4@NiV-LDH/NF-2 composite material as the positive electrode and biochar (BC) as the negative electrode. Notably, under the condition of a power density of 749.98 W kg−1, the energy density of the NiCo2S4@NiV-LDH/NF-2//BC device is 120.81 Wh kg−1. In addition, NiCo2S4@NiV-LDH/GCE also showed excellent performance in the detection of tryptophan due to its superior catalytic performance. The low detection limit of NiCo2S4@NiV-LDH/GCE sensor is 0.46 μM, the wide linear range is 0.5–153 μM, and the highest sensitivity.