FeOOH-Catalyzed Heterogeneous Electro-Fenton System upon Anthraquinone@Graphene Nanohybrid Cathode in a Divided Electrolytic Cell: Catholyte-Regulated Catalytic Oxidation Performance and Mechanism

The aim of the present work was to illuminate the catholyte-regulated catalytic oxidation performance and mechanism of the FeOOH-catalyzed heterogeneous electro-Fenton (Hetero-EF) system operating in a divided electrolytic cell. Depending on pH evolution with electrolysis time, the effect of the catholyte type on the H 2 O 2 yield and current efficiency was investigated on an anthraquinone@electrochemically reduced grapheme oxide nanohybrid cathode. Based on the physicochemical characterization of the supported FeOOH nanoparticles, it was found that the Hetero-EF system exhibits the synchronous role of coupled adsorption and electrocatalytic oxidation for rhodamine B (RhB) degradation, with a higher apparent rate constant in MgSO 4 catholyte and a higher mineralization rate in Na 2 SO 4 catholyte. The catholyte-regulated catalytic oxidation mechanism was proposed according to radical scavenging experiments. In MgSO 4 catholyte, the Hetero-EF process follows a classic Haber-Weiss mechanism mediated by the dissolved iron ions and surface iron species to generate •OH, while in Na 2 SO 4 catholyte, the catalytic decomposition of H 2 O 2 by surface iron species and the deactivation of ≡Fe III -OH·H 2 O 2 complex to form HO • 2 (O 2 • − ), •OH and ferryl species (≡Fe IV = O). X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy measurements revealed the desirable stability of Hetero-EF system after multiple reutilizations.