Electrochemical oxidation and advanced oxidation processes using a 3D hexagonal Co 3 O 4 array anode for 4-nitrophenol decomposition coupled with simultaneous CO 2 conversion to liquid fuels via a flower-like CuO cathode.

A novel electrocatalytic system was developed to realize one-pot conversion of organic pollutants into liquid fuels such as methanol (CH ₃ OH) and ethanol (C ₂ H ₅ OH). The process combines the catalytic oxidation of organic pollutants with electrocatalytic reduction of CO ₂ . We first coupled the electrocatalytic process with SO ₄ ^•- -based advanced oxidation processes (AOPs) for the degradation of 4-nitrophenol (4-NP) using a 3D-hexagonal Co ₃ O ₄ anode. In this step, 4-NP was mineralized to CO ₂ , and then the CO ₂ was converted to CH ₃ OH and C ₂ H ₅ OH by electrocatalytic reduction using a flower-like CuO cathode. The experimental results show the destruction of 4-NP (60 mL, 10 mg/L) can be as high as 99%. In addition, the yields of CH ₃ OH and C ₂ H ₅ OH were 98.29 μmol/L and 40.95 μmol/L, respectively, which represents a conversion of 41.8% of 4-NP into liquid fuels; the electron efficiency was 73.1%. In addition, we found that 3D-hexagonal arrays of Co ₃ O ₄ with different morphologies can be obtained by adding different amounts of urea. We also investigated the formation mechanism of novel 3D-hexagonal Co ₃ O ₄ arrays for the first time. A mechanism was proposed to explain the electrocatalytic steps involved in the conversion of 4-NP to CH ₃ OH and C ₂ H ₅ OH and the synergetic effects between AOPs and electrocatalysis.
(Copyright © 2018 Elsevier Ltd. All rights reserved.)