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

Abstract

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 In recent years, electrochemical advanced oxidation processes (EAOPs) have received increasing attention due their high effectiveness in the degradation of refractory organic pollutants via hydroxyl radicals (•OH) and superoxide radicals (O1-9 Brillas and coworkers have extensively reviewed the applications of EAOPs for the efficient degradation and mineralization of organic contaminants. [1][2][3][4] Among EAOPs, the electro-Fenton (EF) processes generally operate in two types of reactors, undivided cells and divided cells. The majority of studies have been performed in undivided electrochemical cells, 2 where the electrolysis requires a lower cell voltage because of the low voltage loss in the absence of separator. However, it is more difficult to discuss the oxidation mechanism of the EF process in an undivided cell due to the disturbance of reactive oxygen species and other weaker oxidants generated at the anodes.2 In comparison, divided cells are favorable for investigating the reaction mechanism of the EF process. Moreover, the current efficiency and H 2 O 2 yield are universally higher than those obtained in an undivided cell, 2,10 where the simultaneous anodic oxidation of the generated H 2 O 2 takes place.To overcome the defects of the homogeneous EF (Homo-EF) processes, heterogeneous electro-Fenton (Hetero-EF) processes have been developed over a wider applicable pH range. To date, three types of heterogeneous catalysts have been investigated in Hetero-EF system: (i) natural mineral, 11,12 (ii) supported transitional metal oxides, 13,14 [25][26][27][28] Of these, the polymorphs of FeOOH such as goethite (α-FeOOH), lepidocrocite (γ-FeOOH), akaganèite (β-FeOOH), and feroxyhyte (δ-FeOOH) have attracted great attention due to their outstanding catalytic properties, wide-operating pH range, ...

Electrochemical mineralization of sulfamethoxazole over wide pH range using FeIIFeIII LDH modified carbon felt cathode: Degradation pathway, toxicity and reusability of the modified cathode

“…4). The excellent mineralization of SMT achieved with Fe II Fe III LDH/CF at both acidic and basic pH can be attributed to surface catalyzed decomposition of H2O2 to produced • OH which can easily oxidized SMT and its oxidation intermediates [13,18].…”

“…Also, the need for post-treatment neutralization and formation of iron-rich sludge encounter in conventional EF system is completely eliminated with the use of solid catalyst. Based on literature, heterogeneous catalysts such as natural Fe minerals [15][16][17][18][19], supported transition metal/metal oxides [11,[20][21][22][23][24], and transition metals dopedcarbon aerogel [25][26][27][28] have been studied for degradation of the various class of organic pollutants. Excellent mineralization of organics as a result of both homogeneous and surface catalyzed process has been reported for iron containing minerals as heterogeneous catalysts in HEF especially at acid pH, however such system demonstrated low recyclability.…”

Enriched Photoelectrochemical Performance of Phosphate Doped BiVO4Photoelectrode by Coupling FeOOH and rGO

“…These peaks are assigned to Fe 2p 3/2 , the satellite peak (approximately 8.2 eV higher than the Fe 2p 3/2 main peak), and Fe 2p 1/2 in Fe 2 O 3 or FeOOH, respectively. 44,45 The increase in the surface-OH groups and the presence of Fe 3+ suggest that Fe species exist in the form of FeOOH in FeOOH/P:BiVO 4 and FeOOH/P:BiVO 4 /rGO.…”

Synthesis of Three-Dimensional Graphene-Based Hybrid Materials for Water Purification: A Review

“…The proposed 3D electrode was demonstrated to be capable of degrading pollutants much more efficiency than that of commercial carbon electrodes and traditional 2D electrodes. Other GBHMs that have been successfully applied as electrocatalysts and/or electrodes for the oxidative degradation of organic contaminants in wastewater can be found elsewhere [123,124,125,126,127].…”