Degradation of 4-nitrophenol by electrocatalysis and advanced oxidation processes using Co3O4@C anode coupled with simultaneous CO2 reduction via SnO2/CC cathode

Abstract

Herein, we prepared novel three-dimensional (3D) gear-shaped Co3O4@C (Co3O4 modified by amorphous carbon) and sheet-like SnO2/CC (SnO2 grow on the carbon cloth) as anode and cathode to achieve efficient removal of 4-nitrophenol (4-NP) in the presence of peroxymonosulfate (PMS) and simultaneous electrocatalytic reduction of CO2, respectively. In this process, 4-NP was mineralized into CO2 by the Co3O4@C, and the generated CO2 was reduced into HCOOH by the sheet-like SnO2/CC cathode. Compared with the pure Co0.5 (Co3O4 was prepared using 0.5 g urea) with PMS (30 mg, 0.5 g/L), the degradation efficiency of 4-NP (60 mL, 10 mg/L) increased from 74.5%–85.1% in 60 min using the Co0.5 modified by amorphous carbon (Co0.5@C). Furthermore, when the voltage of 1.0 V was added in the anodic system of Co0.5@C with PMS (30 mg, 0.5 g/L), the degradation efficiency of 4-NP increased from 85.1%–99.1% when Pt was used as cathode. In the experiments of 4-NP degradation coupled with simultaneous electrocatalytic CO2 reduction, the degradation efficiency of 4-NP was 99.0% in the anodic system of Co0.5@C with addition of PMS (30 mg, 0.5 g/L), while the Faraday efficiency (FE) of HCOOH was 24.1 % at voltage of −1.3 V using the SnO2/CC as cathode. The results showed that the anode of Co3O4 modified by amorphous carbon can markedly improve the degradation efficiency of 4-NP, while the cathode of SnO2/CC can greatly improve the FE and selectivity of CO2 reduction to HCOOH and the stability of cathode. Finally, the promotion mechanism was proposed to explain the degradation of organic pollutants and reduction of CO2 into HCOOH in the process of electrocatalysis coupled with advanced oxidation processes (AOPs) and simultaneous CO2 reduction.