Enhanced Nonenzymatic Glucose-Sensing Properties of Electrodeposited NiCo₂O₄–Pd Nanosheets: Experimental and DFT Investigations

Here, we report the facile synthesis of NiCo₂O₄ (NCO) and NiCo₂O₄–Pd (NCO–Pd) nanosheets by the electrodeposition method. We observed enhanced glucose-sensing performance of NCO–Pd nanosheets as compared to bare NCO nanosheets. The sensitivity of the pure NCO nanosheets is 27.5 μA μM^–1 cm^–2, whereas NCO–Pd nanosheets exhibit sensitivity of 40.03 μA μM^–1 cm^–2. Density functional theory simulations have been performed to qualitatively support our experimental observations by investigating the interactions and charge-transfer mechanism of glucose on NiCo₂O₄ and Pd-doped NiCo₂O₄ through demonstration of partial density of states and charge density distributions. The presence of occupied and unoccupied density of states near the Fermi level implies that both Ni and Co ions in NiCo₂O₄ can act as communicating media to transfer the charge from glucose by participating in the redox reactions. The higher binding energy of glucose and more charge transfer from glucose to Pd-doped NiCo₂O₄ compared with bare NiCo₂O₄ infer that Pd-doped NiCo₂O₄ possesses superior charge-transfer kinetics, which supports the higher glucose-sensing performance.