Synergetic activation of H2O2 by photo-generated electrons and cathodic Fenton reaction for enhanced self-driven photoelectrocatalytic degradation of organic pollutants

Abstract

In this work, a self-driven photocatalytic fuel cell (PFC) system was constructed, which consisted of a noble metal-free Cu2O/CuO photocathode and a semi-transparent BiVO4 photoanode. The proposed PFC system was used for the degradation of phenol and the removal efficiency of phenol using BiVO4-Cu2O/CuO system was higher than the PFC using Pt cathode (BiVO4-Pt, 67.3%) and bare Cu2O cathode (BiVO4-Cu2O, 84.6%). The short circuit photocurrent of the BiVO4- Cu2O/CuO system was 0.30 mA cm−2, which was higher than the sum of photocurrents generated by the other two photoelectrodes. This could be attributed to the self-driven bias induced by the good match of Fermi levels (EFs) between the BiVO4 and the heterojunction Cu2O/CuO electrode. The addition of 5 mM H2O2 to the PFC system greatly enhanced the degradation process, with the pseudo-first-order kinetic rate constant increased from 0.136 to 2.568 h-1 after the addition of H2O2. Compared with traditional Fenton and Cu-based Fenton-like process, the PFC-H2O2 system has advantages of the broad working pH range (4–7), zero formation of ferric hydroxide sludge and less copper leaching. The X-ray photoelectron spectroscopy (XPS) analysis confirmed the cycle between Cu(I) and Cu(II) on the surface of Cu2O/CuO photocathode, indicating that a Fenton-like reaction had occurred on Cu2O/CuO photocathode. The H2O2 was activated by both the photo-generated electrons and the Cu2O/CuO cathode, which further increased the degradation efficiency of phenol. Furthermore, a high stability was exhibited by the H2O2-PFC system.