Synergistic oxygen vacancy-rich CuO/visible light activation of peroxymonosulfate for degradation of rhodamine B: fast catalyst synthesis and degradation mechanism

This work outlines the synthesis of copper oxide nanoparticles (CuO-SC) loaded with a number of oxygen vacancies by a fast sodium citrate assisted precipitation method with no need of calcination. X-ray diffraction, scanning electron microscopy, UV-Vis diffuse reflectance spectroscopy, time-resolved fluorescence lifetime and electrochemical impedance spectra were used to characterize the as-synthesized nanocomposites. The results indicated that the CuO-SC nanoparticles had regular fusiform shape with high surface area, wide light harvesting window, fast charge transport and high carrier concentration. As a result, the catalytic activity of the CuO-SC/peroxymonosulfate (PMS)/visible light (Vis) system for the degradation of rhodamine B (RhB) was much higher than that of as-prepared CuO nano powder in the absence of sodium citrate. Almost 98.0% of the initial RhB dyes was decomposed in 20 min with 0.12 g L-1 PMS and 0.3 g L-1 catalyst. Meantime, it exhibited high catalytic stability with little deactivation after four runs and a wide application range of pH. Moreover, RhB can be readily degraded with backgrounds of Cl-, NO3-, SO42-, HCO3- and low concentration of humic acid in a CuO-SC/PMS/Vis system. Combined with the results of electron spin resonance paramagnetic spectroscopy, X-ray photoelectron spectroscopy and radical quenching experiments, holes, superoxide radicals and a small amount of sulfate radicals, hydroxyl radicals and singlet oxygen were involved in the CuO-SC/PMS/Vis system. Furthermore, a possible degradation mechanism based on the synergistic effect of radical reaction and non-radical reaction was proposed based on the above results.

Automated summary

This work presents the synthesis of copper oxide nanoparticles (CuO-SC) with oxygen vacancies using a fast sodium citrate assisted precipitation method. The as-synthesized CuO-SC nanoparticles exhibit a regular fusiform shape, high surface area, wide light harvesting window, fast charge transport, and high carrier concentration. The CuO-SC/peroxymonosulfate (PMS)/visible light (Vis) system shows higher catalytic activity for the degradation of rhodamine B (RhB) compared to CuO nano powder without sodium citrate. The system also demonstrates high catalytic stability and wide pH range. The degradation mechanism involves holes, superoxide radicals, sulfate radicals, hydroxyl radicals, and singlet oxygen.