Synergistic electrocatalytic performance of nano-sized 1D Pd-MOF/NF for urea oxidation in alkaline media

Urea is widely recognized as a promising energy source due to its abundance in the environment. Its electrooxidation offers a sustainable pathway for hydrogen generation and wastewater treatment. In this work, a nano-sized one-dimensional palladium metal-organic framework (1D Pd-MOF) was synthesized via a chemical route and drop-cast onto nickel foam (NF), serving as an efficient catalyst promoter for the electrooxidation of urea. The fabricated electrodes were characterized using SEM coupled with EDX and elemental mapping, ICP-OES, XRD, and XPS. Electrochemical evaluations revealed a substantial enhancement in urea oxidation current density, achieving 43 mA cm −2 on the 1D Pd-MOF/NF electrode, compared to 10 mA cm −2 on bare NF. Repeated cyclic voltammetry and chronoamperometry tests confirmed the enhanced stability of the 1D Pd-MOF/NF electrode under operating conditions. Furthermore, the heterogeneous rate constant for urea oxidation was significantly higher on the 1D Pd-MOF/NF electrode (1.73 × 10 5 mol −1 cm 3 s −1 ) than on NF (2.5 × 10 4 mol −1 cm 3 s −1 ). Anodic Tafel slope values of 136 and 113 mV dec −1 for NF and 1D Pd-MOF/NF, respectively, indicate facile urea oxidation at the 1D Pd-MOF/NF electrode. However, the significantly lower charge-transfer resistance of 1.84 Ω cm 2 on the 1D Pd-MOF/NF electrode highlights its superior charge-transfer kinetics and overall electrocatalytic performance for urea oxidation. The CV and EIS results indicate that urea electrooxidation proceeds via a mixed kinetic mechanism, involving both surface-confined and diffusion-controlled processes.