Synthesis and characterization of a layered double hydroxide as a novel, stable, and regenerable electrocatalyst for methylene blue elimination

Abstract

This study aimed to create an affordable and effective electrocatalyst for removing methylene blue (MB). CuZnCr-layered double hydroxide was successfully prepared by a simple co-precipitation method. It was examined using various techniques including X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), X-ray fluorescence (XRF), Energy dispersive X-ray (EDX), and Thermogravimetric analysis (TGA), and then utilized for the electro-oxidation of MB. A UV–visible spectrophotometer was used to examine the impact of different operating parameters. The experimental findings revealed that the optimal applied potential, sodium chloride concentration, and operating time for complete discoloration of MB solution (10 mg.L⁻¹) at neutral pH are 5 V, 0.05 M, and 30 min, respectively. As the initial MB concentration decreased and the chloride concentration increased, the degradation reaction kinetics accelerated, and followed the pseudo-first-order model. Significant removal efficiency was achieved at various pH values but lower pH was more favorable because of the inhibition of the oxygen evolution reaction. It is worth highlighting that CZC-LDH facilitates Cl adsorption for the ClOR (Chloride Oxidation Reaction) leading to the production of active chlorine contributing to indirect oxidation of MB. An increase in the production rate of active chlorine improved the oxidation process by increasing the applied potential. Enhancing the dye degradation was accomplished by combining electrochemical oxidation with solar photolysis. According to the results, the CZC-LDH electrode demonstrated good reusability and stability. Compared with previously published studies, this LDH electrode is low-cost, easy to prepare, and efficient.