Novel multiphase composite electrode decorated with Pd nanoparticles for electrochemical determination of herbicides

This study investigates the electrochemical determination of dicamba (3,6-dichloro-2-methoxybenzoic acid, DIC) and 2,4-D-dichlorophenoxyacetic acid (2,4-D) using a palladium (Pd)-decorated multiphase composite electrode (TiN/Ti_1.886O₃/MgTiO₃/Mg₂TiO₄) denoted as Pd@MPC. The synergistic coexistence and contact between these phases improved the electrochemical performance of the material and provided complementary properties such as electrical conductivity (from TiN and Pd), chemical stability (of MgTiO₃), and surface reactivity (of Ti_1.86O₃ and Pd), which are crucial for efficient electroanalytical applications. The electrode material was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM), which confirmed the successful incorporation of Pd nanoparticles and significantly improved the catalytic properties. Pd, which is known for its excellent electrocatalytic activity, especially in oxidation reactions, facilitates the electrochemical detection of pesticides such as DIC and 2,4-D. The Pd nanoparticles likely serve as active sites for the oxidation of pesticides and improve the sensitivity and selectivity of the sensor. Voltammetric analyses showed that the Pd@MPC/GC electrode exhibited significantly better electrocatalytic activity compared to a commercially available glassy carbon electrode. The results showed that pH strongly influenced the signal-to-noise ratio, with optimal analytical performance achieved at pH 2.0. The developed method showed linearity within a concentration range of 4.99 to 53.82 ng/mL, with correlation coefficients of r = 0.998 for DIC and r = 0.990 for 2,4-D, and a detection limit of 3.03 ng/mL. Recovery tests in river water samples showed a recovery rate of 101%, which is consistent with the results of the HPLC/DAD method used as a comparative method. These results underline the effectiveness of the Pd@MPC/GC electrode for environmental monitoring applications.