Insights into the removal of chloramphenicol by electrochemical reduction on Pd/NiFe-MOF/foam-Ni electrode: Performance and mechanism

To effectively improve the particle dispersion of the catalytic metal and catalytic activity of the palladium electrode, a new type of efficient Pd/NiFe-MOF/foam-Ni composite electrode was prepared. The results showed that the reaction rate constant of chloramphenicol (CAP) by Pd/NiFe-MOF/foam-Ni was three times that of Pd/foam-Ni. X-ray absorption fine structure (XAFS) results showed that palladium on Pd/NiFe-MOF/foam-Ni had a lower oxidation state than that on Pd/foam-Ni. The Pd nanoparticles were uniformly dispersed on the composite electrode and had a small particle size. The electrode had good resistance to sulfites and the electrocatalytic activity was hardly affected in the presence of Cl^-, NO₃^-, HCO₃^-, CO₃^2- and Ca²⁺ in wastewater. Besides, the introduction of nickel-iron bimetallic organic framework (NiFe-MOF) increased the electron density of Pd, improved the dispersion and electrochemical active surface area (ECSA) of Pd. The reaction pathway of CAP was proposed, and the ecotoxicity of CAP and its products was evaluated by the Ecological Structure Activity Relationships (ECOSAR) model. Combined experimental data and density functional theory (DFT) analysis enable us to propose the hydrodechlorination mechanism of CAP on the Pd/NiFe-MOF/foam-Ni electrode. The Pd/NiFe-MOF/foam-Ni composite electrode has good application prospects in the treatment of organic pollutants in wastewater and other environmental remediation applications.