Highly effective CuO catalysts synthesized by various routes for discoloration of methylene blue

A series of CuO catalysts were fabricated through hydrothermal process, thermal decomposition of the precursors of CuC2O4 synthesized by soft reactive grinding route and oxalate-gel co-precipitation method, respectively. The discoloration of methylene blue in the presence of H2O2 was selected as the activity test model reaction. The as-prepared catalysts were characterized by powder X-ray diffraction, scanning electron microscopy, infrared diffuse reflectance spectrum, and N2-adsorption analysis. The CuO obtained from calcination of dry-grinding-derived oxalate precursor has better catalytic performance than those prepared by conventional wet-chemical method. Examination of the structural characterization shows that the small particle size and relatively high surface area are the main reasons for its excellent activity. Moreover, the pseudo-first-order kinetics model was also employed to understand the discoloration behavior of grinding-derived CuO and the activation energy was calculated to be 56.5 kJ mol−1. The current preparation mechanism of solid-state synthetic technique was also proposed by tracking the precursor structure.