Rational design of dual-functional MOF/layered double hydroxide/Prussian blue analogue heterostructures for enhanced energy storage and electrocatalytic performance

Layered double hydroxide (LDH) is considered an ideal electrode material for both energy storage and catalysis due to its excellent theoretical capacitance and electrocatalytic activity. However, LDH exhibits poor conductivity and is prone to agglomeration. Therefore, the rational design of heterogeneous electrode materials with a core-shell structure is an effective strategy for enhancing electrochemical performance. Herein, a bifunctional heterostructure composite (NiCo MOF/LDH/PBA) for supercapacitors and glucose sensors is synthesized by sequentially modifying LDH and then Prussian blue analogue (PBA) onto the surface of NiCo metal organic framework (MOF) via a sequential solvothermal method. The designed heterostructure significantly enhances electron transfer rate of MOF/LDH, endowing it with outstanding electrochemical energy storage and glucose catalytic capabilities. The optimized electrode material (NiCo MOF/LDH-A/PBA) exhibits a specific capacitance of 2546.7 F g⁻¹ at 0.5 A g⁻¹. The assembled NiCo MOF/LDH-A/PBA//AC asymmetric supercapacitor exhibits an energy density of 31.97 Wh kg⁻¹ at 733.05 W kg⁻¹ and a capacitance retention rate of 80.16% after 6000 cycles at a current density of 5 A g⁻¹. Additionally, the NiCo MOF/LDH-A/PBA heterostructure electrode exhibits a high sensitivity (2321 μA mM⁻¹ cm⁻²), a low detection limit (0.99 μM, S/N = 3), a broad linear range (6.67 μM-11.8 mM), excellent interference resistance, and good stability for glucose detection. This work provides new insights into the application of heterostructure electrodes in energy storage/catalytic bifunctional devices.