Experimental and DFT computation studies on NiMn₂O₄ nanoflake-based electrode for the monitoring of metformin in the aquatic environment

Transition metal oxides, particularly spinel nickel manganese oxide (NiMn₂O₄) nanomaterials, have shown promising electrochemical properties owing to their multiple oxidation states and tunable electronic properties. This study investigates the synthesis of NiMn₂O₄ nanoflakes (NFs) and their application as a sensor electrode for electrochemical sensing, aiming to detect Metformin (MET), a pharmaceutical pollutant. The morphological and phase analysis depicted the well-defined interconnected nanoflake (NFs) morphology and a typical cubic spinel crystalline phase. The computational studies, DFT calculations, revealed the interaction of MET and the surfaces of NiMn₂O₄, which evidenced that the adsorption process was thermodynamically favorable with an adsorption energy of −2.99 eV. As a sensing electrode, the NiMn₂O₄ NF-modified electrode exhibited a clear redox reaction with a high oxidation potential upon exposure to MET. A reproducible sensitivity of ∼17.8514 μA/μMcm² and a low detection limit of ∼19.876 μM with a correlation coefficient (R) of ∼0.9989 were recorded by the NiMn₂O₄ NF-modified electrode toward the detection of MET. This study provides a novel integration of experimental electrochemical sensing and DFT-based mechanistic insights, demonstrating the strong chemisorption-driven detection of MET on NiMn₂O₄ NFs. The combined structure to property to performance correlation establishes NiMn₂O₄ NFs as a promising platform for reliable pharmaceutical pollutant monitoring.