Enhanced Creatinine Adsorption Kinetics on Defective Polyhedral Morphology of Cu 2 O‐CuO@Pt ( 3d‐2p‐5d ) Nanohybrids for Electrochemical Sensing Application and DFT Investigation

In this study, the defective polyhedral Cu₂O-CuO@Pt-X (where X represents different Pt loading concentrations ranging from 0.005 to 0.25 m or 2-10 mg) was synthesized through a hydrothermal method combined with ultrasonic techniques. The concrete evidence from EPR, XPS, and HR-TEM confirms that the Cu₂O-CuO@Pt-X polyhedral structure exhibits remarkable defective sites (OV_s and screw dislocation), heterointerfaces, and Pt cluster formation compared to different Pt dopings. Furthermore, the modified electrode surface achieves a broad linear range of 0.01-500 µm and a detection limit as low as 0.0015 µm in 0.05 m PBS for the detection of creatinine (Crt). Based on the DFT study, the adsorption energies of Crt-NH₂ (∼ -1.3551 eV), Crt-NHOH (∼ -1.896 eV), and Crt-NO (∼ -1.2041 eV) were calculated at the different metal cation sites on the Cu₂O-CuO@Pt surfaces. The CV and DPV measurements also reveal that the oxime group (─NHOH) exhibits significantly higher adsorption energy, as evidenced by its lower onset potential and earlier oxidation behavior. Besides, the d-band center (Ɛ_d) can be calculated by the PDOS data, such as Cu₂O-CuO@Pt (-0.5316 eV), Cu₂O-CuO (-2.6095 eV), Cu₂O (-1.7189 eV), CuO (-2.4178 eV), and Pt (-0.3599 eV), respectively. These findings suggest that the higher attraction of Cu₂O-CuO@Pt for Crt-NH₂ adsorption at the electrode interface is made due to its reduced d-band center energy, robust orbital hybridization, and increased electron cloud density. Ultimately, this work schematically illustrates the generation of OV_s within the crystal lattice, the heterointerface between Cu₂O and CuO, and the labile electron transfer mechanism in the defective polyhedral Cu₂O-CuO@Pt-X.