Ultrafast O2 activation by copper oxide for 2,4-dichlorophenol degradation: The size-dependent surface reactivity

This study demonstrated interesting ultrafast activation of molecular O₂ by copper oxide (CuO) particles and very rapid elimination of aqueous 2,4-dichlorophenol (2,4-DCP) within reaction time of 30 s. Electron paramagnetic resonance (EPR) characterization indicated that OH, Cu³⁺, ¹O₂ and O₂⁻ were generated in the CuO/O₂ systems, wherein O₂⁻ would be the main reactive species responsible for 2,4-DCP degradation. It was further found that the catalytic ability of CuO for O₂ activation was highly size dependent and nano-CuO was far reactive than micro-CuO. H₂ temperature-programmed reduction (H₂-TPR), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM) analyses revealed that both the quantity and the reactivity of the surface reaction sites (surface Cu⁺ and O₂) could determine the catalytic ability of CuO affecting efficient Cu⁺-based molecular oxygen activation. Moreover, the O₂ activation ability of CuO would depend on not only the dimension, but also crystalline factors, for example, the exposed facets.