Carbon nitride compounds (CN) complexed with the in-situ-produced Cu(II) on the surface of CuAlO substrate (CN-Cu(II)-CuAlO) is prepared via a surface growth process for the first time and exhibits exceptionally high activity and efficiency for the degradation of the refractory pollutants in water through a Fenton-like process in a wide pH range. The reaction rate for bisphenol A removal is ∼25 times higher than that of the CuAlO. According to the characterization, Cu(II) generation on the surface of CuAlO during the surface growth process results in the marked decrease of the surface oxygen vacancies and the formation of the C-O-Cu bridges between CN and Cu(II)-CuAlO in the catalyst. The electron paramagnetic resonance (EPR) analysis and density functional theory (DFT) calculations demonstrate that the dual reaction centers are produced around the Cu and C sites due to the cation-π interactions through the C-O-Cu bridges in CN-Cu(II)-CuAlO. During the Fenton-like reactions, the electron-rich center around Cu is responsible for the efficient reduction of HO to OH, and the electron-poor center around C captures electrons from HO or pollutants and diverts them to the electron-rich area via the C-O-Cu bridge. Thus, the catalyst exhibits excellent catalytic performance for the refractory pollutant degradation. This study can deepen our understanding on the enhanced Fenton reactivity for water purification through functionalizing with organic solid-phase ligands on the catalyst surface.
The application of the classical Fenton reaction has long been limited by several problems, such as metallic sludge and narrow pH range, which derived from the metal components in the catalyst. Developing a metal-free Fenton catalyst may efficiently address these problems. Here, we firstly perform a density functional theory (DFT) study to explore the possibility of developing the 4-phenoxyphenol moleculedoped reduced graphene oxide nanocomposite (rGO-4-PP Nc) as a metal-free Fenton-like catalyst by tuning the electron distribution. The theoretical calculation results reveal that rGO-4-PP Nc can act as an efficient Fenton-like catalyst for H 2 O 2 activation and pollutant degradation through formation of electron-rich O and electron-deficient C centers on the C-O-C bridge. The actual rGO-4-PP Nc is also prepared via a surface complexation and copolymerization process. The experimental evidence, such as that gained from XRD, FIIR and EPR analysis, confirm the theoretical models and the dual-reactioncenter Fenton-like mechanism. This work provides a basis for theoretical calculation to guide the actual synthesis and prediction of catalytic activity of the Fenton-like catalysts, and also offers a creative perspective to develop new generation metal-free Fenton catalysts by tuning the electron distribution using organic polymers.
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