Three-dimensional functional carbon nanotube architecture as a highly efficient and active indirect catalyst for degradation of 4-chlorophenol

Abstract

Electro-Fenton (EF) is a promising and green technology for environmental remediation. However, traditional EF often suffers from iron sludge production, leading to poor pH adaptation and secondary pollution. In this work, we synthesized a three-dimensional (3D) carbon nanotube architecture containing nitrogen and oxygen heteroatoms on carbon fibre paper (3D-NOCNTs/CFP) as an indirect catalyst for a metal-free EF process for the removal of 4-chlorophenol (4-CP). The dependence of the content and the type of the functional groups in the carbon plane on the pyrolysis temperature was studied through XPS measurements. This binder-free electrode has been identified as a bifunctional catalyst that can catalyze a high H2O2 yield process and a subsequent in-situ generation of ⋅OH via an O2 reduction reaction (ORR). Thus the generated ⋅OH radicals can directly participate in the oxidative degradation of 4-CP and the utilization of iron can be avoided in the EF process. The optimized electrode could remove 99.3 % 4-CP in 120 min and exhibits a broad suitability upon pH, an excellent capability, and a prominent stability for the degradation of 4-CP. The mechanism was explained by density function theory (DFT) calculations and the controlled experiments. Such a metal-free EF process features a promising green technology for the oxidative degradation of organic pollutants.