photoelectro-Fenton Process Research Articles

Replacing carbon cloth by nickel mesh as substrate for air-diffusion cathodes: H2O2 production and carbenicillin degradation by photoelectro-Fenton

The development of air-diffusion electrodes (ADEs) that electrocatalytically produce H2O2 for its decomposition by Fenton’s reaction is gaining relevance. However, attention has been paid to improve the catalytic layer using standard carbonaceous substrates like Ccloth. This work clearly proves the superior endurance of 3 cm2 ADEs fabricated with Nimesh as substrate, achieving stable H2O2 accumulation up to 60 mM at 100 mA for 48 h in an undivided cell. Consequently, the antibiotic carbenicillin could be totally degraded in 13 min by photoelectro-Fenton (PEF) process using the Nimesh|C-PTFE ADE at 20 mA in an acidic model solution. This high performance was confirmed by PEF treatment in urban wastewater, reaching total drug disappearance in 18 min with >80 % TOC abatement. The time course of OH and toxicity was monitored, whereas chromatographic analysis of treated solutions revealed the formation of 32 aromatic and 16 aliphatic byproducts, including 7 linear carboxylic acids.

Removal of contaminants of emerging concern by solar photo electro-Fenton process in a solar electrochemical raceway pond reactor

This work proposes the degradation of different contaminants of emerging concern (CECs) present in a secondary effluent from a municipal wastewater treatment plant in a solar electrochemical raceway pond reactor (SEC-RPR), applying the solar photo electro-Fenton (SPFE) process. Tap water and a secondary effluent were enriched with 100 µg L−1 of 7 CECs to study the degradation of these compounds by the SPEF process in a SEC-RPR. Among the results obtained, an elimination over 96% and 90% of 5 CECs (progesterone, estradiol, ibuprofen, diclofenac and estrone) was achieved, while sulfamethazine and carbamazepine were eliminated by 73, 37% and 80, 66% after 1 h of treatment, respectively. In turn, a secondary effluent that already achieved the minimum organic load standards established by Chilean regulations was treated in a SEC-RPR by applying different electrochemical advanced oxidation processes (EAOPs). However, regardless of the applied treatment (SPEF, electro-Fenton and electro-oxidation/H2O2), it was possible to further reduce the organic content and even mineralize it. These experiments were performed at pH 3, with Na2SO4 0.05 mM, Fe2+ 0.05 mM and applying a current density of 20 mA cm−2. The SPEF process implemented in a SEC-RPR is presented as an excellent alternative for the treatment of municipal wastewater, due to the large contact area between the effluent and UV radiation, in addition to the continuous and homogeneous generation of H2O2, which allows for the production of hydroxyl radicals in solution, favoring the degradation and mineralization of pollutants.

Removal of Eosin Yellow dye from industrial wastewater using UV/H2O2 and photoelectro-Fenton techniques

This work investigates the feasibility of applying photochemical advanced oxidation as a viable technique to overcome the ecological issue of stubborn organic contaminants. UV/H2O2 and photoelectro-Fenton processes were used for degradation of Eosin Yellow in its solutions. The operational variables examined for UV/H2O2 are solution pH, initial concentration of dye, H2O2 dosage and superficial velocity of oxygen sparging. Meanwhile, oxygen flow rate, applied current density, initial concentration of dye and the cathode thickness were tested for photoelectro-Fenton method. Decolorization was achieved by 99.9 % removal using UV/H2O2 method within 60 min at 200 ppm Eosin Yellow concentration and 50 mM of H2O2 and superficial oxygen velocity of 5 cm/s. The optimum conditions of photoelectro-Fenton method are 200 ppm initial concentration of Eosin Yellow dye with pH 3, superficial oxygen velocity 2.5 cm/s, applied current density 1 mA/cm2 and three layer of graphite cathode. The degradation rate was found to follow a pseudo-first order reaction kinetics. To assist in the economic evaluation of the two techniques energy consumption was calculated, the electrical energy required for the treatment of 1 m3 of Eosin Yellow dye solution was found to be 15 and 18.88 kW∙h/m3 for UV/H2O2 and photoelectro-Fenton processes, respectively. The cost of chemicals consumed in the UV/H2O2 process should be also considered in comparing the two methods.

Using Au NPs anchored on ZrO2/carbon black toward more efficient H2O2 electrogeneration in flow-by reactor for carbaryl removal in real wastewater

In the present study, we designed a highly efficient catalyst for H2O2 production using gold nanoparticles (Au NPs) anchored on hybrid substrate composed of ZrO2 and Printex L6 carbon (Au-ZrO2/PL6C). The higher selectivity of Au-ZrO2/PL6C (97%) toward H2O2 electrogeneration and its improved activity in terms of ORR onset potential (140 mV for more positive values) compared to Au/PL6C (80%) were attributed to the synergism between Au NPs anchored on ZrO2/PL6C hybrid support. The results obtained from the application of the catalysts for H2O2 generation on gas diffusion electrode (GDE) after 120 min of electrolysis reflected the following order of efficiency: PL6C (∼140 mg L−1) < ZrO2/PL6C (∼235 mg L−1) < Au/PL6C (∼374 mg L−1) < Au-ZrO2/PL6C (∼600 mg L−1). Given that Au-ZrO2/PL6C exhibited the highest catalytic efficiency, this catalyst was employed for the removal of carbaryl (CBR) using different electrochemical advanced oxidation processes. The CBR degradation tests exhibited pseudo first-order kinetics, with the electro-Fenton (EF) and photoelectro-Fenton (PEF) processes recording the fastest removal kinetics (3.5 × 10−2 s−1 and 4.1 × 10−2 s−1, respectively). The PEF process exhibited the highest efficiency in terms of organic by-products mineralization; this was attributed to the additional photodecarboxylation of the Fe(III)-RCOOH complexes by UVC light. The aromatic by-products, short chain carboxylic acids, and ionic nitrogen species produced during the mineralization process contributed to the successful degradation of CBR. Apart from the analysis with synthetic water, the study also analyzed the treatment of urban wastewater spiked with CBR using a pre-pilot flow plant.

Novel biodegradable two-dimensional vanadene augmented photoelectro-fenton process for cancer catalytic therapy

Fenton reaction-based chemodynamic therapy is hardly a self-sufficient cancer treatment, due to its stringent reaction conditions, limited substrate concentration, and negative feedback from the tumor microenvironment. Herein, we synthesized a novel two-dimensional (2D) vanadium-based nanosheets (Vanadene, V NSs) with polyvalent surfaces (VIV/VV), a very narrow band gap of 0.8 eV, and high biodegradability by a liquid-phase exfoliation strategy. The polyvalent surface endowed its multiple capabilities to modulate TME through GSH consumption and O2 production via VV and to catalyze a Fenton-like reaction to produce ·OH under a mild condition via VIV. In addition, efficient energy conversions including near-infrared (NIR)-thermal conversion (photothermal therapy, PTT) and NIR-electron conversion (photodynamic therapy, PDT) were ensured by the narrow band gap, in which NIR-thermal conversion enhanced the Fenton-like reaction activity through accelerating ionization while NIR-electron conversion catalyzed the conversion of O2 to ·O2− for further breaking redox homeostasis. Moreover, V NSs-based nanocatalyst can be slowly degraded into non-toxic species, enabling it to be innocuously eliminated from the body after completing tumor eradication by single drug injection and single NIR irradiation. Therefore, this study provides new insights into a universal nanoplatform for NIR-enhanced combination cancer therapy, highlighting the utility of 2D V NSs in the field of biomedicine.

Development of a hybrid bifunctional rotating drum electrode system for the enhanced oxidation of ciprofloxacin: An integrated photoelectrocatalysis and photo-electro-Fenton processes

Mismanaged antibiotics ending up in aquatic environment due to inadequate conventional treatment urges the need to develop powerful advanced oxidation techniques. In this study, hybrid bifunctional rotating drum reactor (BRDR) has been developed and its potency in enhancing the degradation of ciprofloxacin has been demonstrated. BRDR is a hybrid reactor that integrates – photoelectrocatalysis (PEC) and photo-electro-Fenton (PEF) processes with UVA irradiation. It consists of MoS2-TiO2-coated carbon cloth as anode and Ferrocene-functionalized graphene-coated graphite felt as cathode. BRDR system significantly improved the removal efficiency (99.9 %) as compared to individual efficiencies of PEC (71 %) and PEF (78.8 %) processes. An increase in electrode rotation speed significantly enhanced the removal without external aeration (0.059 min−1 for 60 rpm). Maximum removal rate was achieved at pH 3 (0.061 min−1) followed by 7 (0.040 min−1) and 9 (0.020 min−1). The increase in applied potential from open circuit voltage to 1.5 V improved the removal rate from 0.005 min−1 to 0.040 min−1. The mechanism of reactive oxygen species production in BRDR system is elaborated. BRDR is demonstrated to be cleaner treatment system which excludes the external chemical addition, aeration, and sludge formation.

Reconstruction of Electronic Structure of MOF-525 via Metalloporphyrin for Enhanced Photoelectro-Fenton Process

Photoelectro-Fenton (PEF) process can continuously promote the occurrence of Fenton reaction and the generation of active species, which is an advanced oxidation technology for pollutant degradation. However, the lack of bifunctional catalysts restricts the development of PEF technology. In this study, the electronic rearrangement MOF-525 modified by metalloporphyrin (named MOF-525-Fe/Zr) was prepared, to load on the carbon felt as a novel cathode catalyst, which is used in PEF process. A series of characterization and photoelectric chemical properties tests combined with DFT calculation showed that the modification of MOF-525 could not only have the large specific surface area and multistage pore structure but also co-stimulate the metal-to-ligand charge transfer (MLCT) and ligand-to-cluster charge transfer (LCCT) by photoelectric synergy. These charge transitions provide periodic electron donor-acceptor conduction paths in MOF-525-Fe/Zr, which can improve the active species formation and transfer efficiency. Owing to their favorable pore and electronic structure as well as stability, MOF-525-Fe/Zr shows great promise for the application in the catalytic process of PEF. Sulfamethoxazole (SMX) degradation was enhanced by MOF-525-Fe/Zr with the TOC removal rate above 75% both in river water and tap water. Finally, the reasonable pathway of PEF catalytic degradation of SMX was proposed by HPLC-MS analysis. In conclusion, this study provides a new idea for reconstructing the electronic structure of MOFs catalyst and broadening the practical application of PEF technology.

Application of electro-Fenton and photoelectro-Fenton processes for the degradation of contaminants in landfill leachate

Worldwide, most solid waste ends its life in landfill sites, which have a significant environmental impact in several respects. In particular, rainfall over landfill sites results in the production of an aqueous leachate containing compounds having low biodegradability, high toxicity, and a high organic load. For this reason, this study aims to investigate the applicability of electro-Fenton (EF) and photoelectro-Fenton (PEF) processes as alternative for treating a local landfill effluent with high organic content (chemical oxygen demand (COD) = 2684.7 mg-O2 L −1) in a continuous-flow reactor (using, for first time, this kind of system with higher electrodes area of 35 cm2) using boron-doped diamond anode (Nb/BDD) and a carbon felt cathode (FC) electrodes. The effects of current density j (30, 60 and 90 mA cm−2) and UV radiation wavelength (UVA and UVC) were studied to evaluate the treatment efficiency as well as the energy consumption. Results clearly showed that, the best efficiencies removing organic matter, in terms of COD, were about 66%, 68% and 89% with an energy consumption of only 19.41, 17.61 and 17.59 kWh kg COD−1 for EF, PEF-UVA and PEF-UVC respectively, at 90 mA cm−2 after 4 h of operation. The treatment of this kind of effluent produced organic and inorganic by-products, the acetic and formic acids as well as NO2−, NO3−, and NH4+, being assessed their concentrations.

Use of WO2.72 Nanoparticles/Vulcan® XC72 GDE Electrocatalyst Combined with the Photoelectro-Fenton Process for the Degradation of 17α-Ethinylestradiol (EE2)

Use of WO2.72 Nanoparticles/Vulcan® XC72 GDE Electrocatalyst Combined with the Photoelectro-Fenton Process for the Degradation of 17α-Ethinylestradiol (EE2)

An efficient simultaneous degradation of sulfamethoxazole and trimethoprim by photoelectro-Fenton process under non-modified pH using a natural citric acid source: study of biodegradability, ecotoxicity, and antibacterial activity.

In this work, the use of natural organic wastes (orange and lemon peels) as sources of citric acid was evaluated along with the application of the photoelectro-Fenton (PEF) system under non-modified pH as a novel alternative to degrade a complex mixture of pharmaceuticals: sulfamethoxazole (SMX-7.90 × 10-5mol/L) and trimethoprim (TMP-6.89 × 10-5mol/L). The system was equipped with a carbon felt air diffusion cathode (GDE) and a Ti/IrO2 anode doped with SnO2 (DSA). A 3.6 × 10-5mol/L solution of commercial citric acid was used as a reference. The pharmaceuticals' evolution in the mixture was followed by high-performance liquid chromatography (HPLC). The addition of natural products showed an efficient simultaneous degradation of the antibiotics (100% of SMX and TMP at 45min and 90min, respectively) similar to the performance produced by adding the commercial citric acid to the PEF system. Moreover, the addition of natural products allowed for an increment of biodegradability (100% removal of TOC by a modified Zahn Wellens test) and a decrease in ecotoxicity (0% in the bioassay with D. Magna) of the treated solutions. The antibacterial activity was eliminated after only 45min of treatment, suggesting that the degradation by-products do not represent a significant risk to human health or the environment in general. Results suggest that, because of the efficient formation of Fe-citrate complexes, the PEF could be enhanced by the addition of natural organic wastes as a sustainable alternative ecological system for water contaminated pharmaceuticals. Additionally, the potential of reusing natural organic wastes has been exposed, contributing to an improved low-cost PEF by decreasing the environmental contamination produced by this type of waste.

Evaluation of the combined Anaerobic Digestion/Solar photoelectro-Fenton process: Removal of organic matter contained in slaughterhouse wastewater

Evaluation of the combined Anaerobic Digestion/Solar photoelectro-Fenton process: Removal of organic matter contained in slaughterhouse wastewater

Insights into Antibiotic Cefaclor Mineralization by Electro-Fenton and Photoelectro-Fenton Processes Using a Ti/Ti4o7 Anode: Performance, Mechanism and Toxic Chlorate/Perchlorate Formation

Insights into Antibiotic Cefaclor Mineralization by Electro-Fenton and Photoelectro-Fenton Processes Using a Ti/Ti4o7 Anode: Performance, Mechanism and Toxic Chlorate/Perchlorate Formation

Bisphenol-S removal via photoelectro-fenton/H2O2 process using Co-porphyrin/Printex L6 gas diffusion electrode

The present work reports the development and application of gas diffusion electrode (GDE) based on carbon Printex L6 modified with 5% Co-Porphyrin/CPL6 for the removal of Bisphenol S (BPS) in wastewater using different electrochemical advanced oxidation processes (EAOPs). The application of the modified GDE led to the in-situ generation of 333 mg L−1 of H2O2 in only 90 min; this represents an increase of 88% in H2O2 generation in relation to the unmodified GDE. The process involving bisphenol S degradation fitted well into a pseudo-first order kinetic reaction for all the treatment techniques evaluated; the treatment techniques investigated recorded an increase in kinetic rate constant in the following order: anodic oxidation (0.004 min−1) < UV-C (0.006 min−1) < H2O2 (0.008 min−1) < H2O2/UV-C (0.016 min−1) < electro-Fenton (0.063 min−1) < photo electro-Fenton (0.154 min−1). The photo electro-Fenton (PEF) process exhibited the best degradation efficiency; BPS was completely removed after only 30 min of treatment and 78% mineralization was recorded after 360 min of treatment. The remaining organic matter under the PEF treatment process corresponded to short-chain carboxylic acids; this confirms the efficiency of the process applied for BPS decontamination. The results obtained show that the proposed treatment mechanism can be successfully combined with cheaper biological treatments for a total remediation of wastes.

Comparative study of the removal of direct red 23 by anodic oxidation, electro-Fenton, photo-anodic oxidation and photoelectro-Fenton in chloride and sulfate media

This study aims to compare the efficiency of anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF), and their association with UV irradiation (photo anodic oxidation (PAO), and photo electro-Fenton (PEF) for the removal of Direct Red 23 from wastewater using a BDD/carbon felt cell in chloride and sulfate medium and in their combination. The effect of the supporting electrolyte was investigated in AO-H2O2 and EF processes. High discoloration efficiency was obtained in chloride media while a higher mineralization rate was achieved in sulfate media. The EF process reached higher total organic carbon (TOC) removal efficiency than AO-H2O2. 90% TOC removal rate was achieved by the EF against 82% by AO-H2O2 in sulfate media. The influence of using the mixt supporting electrolyte formed of 75% Na2SO4 + 25% NaCl was found to have beneficial effect on TOC removal, achieving 89% and 97% by AO-H2O2 and EF, respectively. High currents led to higher mineralization rates while low currents yielded to a higher mineralization current efficiency (MCE%) and lower energy consumption (EC). UV irradiation enhanced process efficiency. Mineralization efficiency followed the sequence: AO-H2O2 < PAO < EF < PEF. The PEF process was able to remove TOC completely at 5 mA cm−2 current density and 6 h of electrolysis with a MCE% value of 16.57% and EC value of 1.29 kWh g−1 TOC removed.

H2O2 production at gas-diffusion cathodes made from agarose-derived carbons with different textural properties for acebutolol degradation in chloride media

The excessive cost, unsustainability or complex production of new highly selective electrocatalysts for H2O2 production, especially noble-metal-based ones, is prohibitive in the water treatment sector. To solve this conundrum, biomass-derived carbons with adequate textural properties were synthesized via agarose double-step pyrolysis followed by steam activation. A longer steam treatment enhanced the graphitization and porosity, even surpassing commercial carbon black. Steam treatment for 20 min yielded the greatest surface area (1248 m2 g-1), enhanced the mesopore/micropore volume distribution and increased the activity (E1/2 = 0.609 V) and yield of H2O2 (40%) as determined by RRDE. The upgraded textural properties had very positive impact on the ability of the corresponding gas-diffusion electrodes (GDEs) to accumulate H2O2, reaching Faradaic current efficiencies of ~95% at 30 min. Acidic solutions of β-blocker acebutolol were treated by photoelectro-Fenton (PEF) process in synthetic media with and without chloride. In urban wastewater, total drug disappearance was reached at 60 min with almost 50% mineralization after 360 min at only 10 mA cm-2. Up to 14 degradation products were identified in the Cl−-containing medium.

Advanced treatment of water contaminated with atrazine, difenoconazole and fipronil mixture, its by-products and bio-toxicity levels

The pesticides atrazine (ATZ), difenoconazole (DFN) and fipronil (FPN) are widely used in different crops. These compounds have been detected in water matrices and present toxic potential to aquatic fauna as well as human health, especially when presented as a mixture of pesticides due to their synergistic effects. Therefore, a mixture of these three pesticides, named ADF, was prepared to investigate the efficiency of degradation of each compound and the mineralization of ADF by the application of a photo-electro Fenton (PEF) process with boron-doped diamond (BDD) anode (PEF-BDD). The concentration of ADF was determined by High-Performance Liquid Chromatography (HPLC) analysis. Preliminary tests were performed, enabling the application of a desirability function and a Response Surface Methodology (RSM) to obtain the optimal operating conditions of the electrolytic cell, namely applied electric current (AEC) of 0.7 A, H2O2 concentration of 1000 mg L−1, and flow rate of 0.6 L min−1, within 15 min of PEF-BDD process, reaching a degradation in the mixture of 95.7% ATZ, 97.3% DFN and 96.5% FPN and mineralization of 47.3% of the ADF solution. Bio-toxicity levels displayed by the bioindicators Artemia salina (acute toxicity) and Allium cepa (cytotoxicity) were assessed and, in addition, a study of intermediate reaction by-products identified by Gas Chromatography-Mass Spectrometry (GC-MS) was carried out. Finally, this study aims to provide a comprehensive understanding of the application potential of the PEF-BDD process for efficient treatment of surface and groundwater contaminated with pesticides in a mixture.

Application of oxidative process to degrade paraquat present in the commercial herbicide

Paraquat is resistant to degradation by conventional treatments, being necessary to use treatments with greater effectiveness, such as advanced oxidative processes. In this work, different advanced oxidative processes were applied (Fenton, electro-Fenton, photoelectro-oxidation and photoelectro-Fenton) employing oxide electrodes to degrade Gramoxone, a commercial herbicide that contains paraquat in its composition. The degradation and formation of by-products were accompanied by high performance liquid chromatography, total organic carbon (TOC) and chemical oxygen demand (COD). The results showed that the photoelectro-Fenton process was the most efficient due to the synergistic effect, reaching 79% degradation of the initial compound and 82% and 71% removal of TOC and COD, respectively. After the application of the electro-Fenton and photoelectro-Fenton oxidation processes, short-chain carboxylic acids such as succinic acid, oxalic acid, acetic acid and formic acid were identified as by-products of the oxidation of Gramoxone. The results were satisfactory and deserve to be highlighted, as a commercial formulation was used, making the scenario more realistic.

Irreversible inactivation of carbapenem-resistant Klebsiella pneumoniae and its genes in water by photo-electro-oxidation and photo-electro-Fenton - Processes action modes

Carbapenem-resistant Klebsiella pneumoniae is a critical priority pathogen according to the World Health Organization's classification. Effluents of municipal wastewater treatment plants (EWWTP) may be a route for K. pneumoniae dissemination. Herein, the inactivation of this microorganism in simulated EWWTP by the photo-electro-oxidation (PEO) and photo-electro-Fenton (PEF) processes was evaluated. Firstly, the disinfecting ability and action pathways of these processes were established. PEO achieved faster K. pneumoniae inactivation (6 log units in 75 min of treatment) than the PEF process (6 log units in 105 min of treatment). PEO completely inactivated K. pneumoniae due to the simultaneous action of UVA light, electrogenerated H2O2, and anodic oxidation pathways. The slower inactivation of K. pneumoniae when using PEF was related to interfering screen effects of iron oxides on light penetration and the diffusion of the bacteria to the anode. However, both PEO and PEF avoided the recovery and regrowth of treated bacteria (with no detectable increase in the bacteria concentration after 24 h of incubation). In addition to the bacteria evolution, the effect of treatment processes on the resistance gene was examined. Despite inactivation of K. pneumoniae by PEF was slower than by PEO, the former process induced a stronger degrading action on the gene, conferring the resistance to carbapenems (PEF had a Ct value of 24.92 cycles after 105 min of treatment, while PEO presented a Ct of 19.97 cycles after 75 min). The results of this research indicate that electrochemical processes such as PEO and PEF are highly effective at dealing with resistant K. pneumoniae in the EWWTP matrix.

Study of degradation of amitriptyline antidepressant by different electrochemical advanced oxidation processes

Amitriptyline (AMT) is the most widely used tricyclic antidepressant and is classified as a recalcitrant emergent contaminant because it has been detected in different sources of water. Its accumulation in water and soil represents a risk for different living creatures. To remove amitriptyline from wastewater, the Advanced Oxidation Processes (AOPs) stands up as an interesting option since generate highly oxidized species as hydroxyl radicals (OH) by environmentally friendly mechanism. In this work, the oxidation and mineralization of AMT solution have been comparatively studied by 3 Electrochemical AOPs (EAOPs) where the OH is produced by anodic oxidation of H2O (AO-H2O2), or by electro-Fenton (EF) or photoelectro-Fenton (PEF).PEF process with a BDD anode showed the best performance for degradation and mineralization of this drug due to the synergistic action of highly reactive physiosorbed BDD (OH), homogeneous OH and UVA radiation. This process achieved total degradation of AMT at 50 min of electrolysis and 95% of mineralization after 360 min of treatment with 0.5 mmol L−1 Fe2+ at 100 mA cm−2. Six aromatic intermediates for the drug mineralization were identified in short time of electrolysis by GC-MS, including a chloroaromatic by-product formed from the attack of active chlorine. Short-chain carboxylic acids like succinic, malic, oxalic and formic acid were quantified by ion-exclusion HPLC. Furthermore, the formation of NO3− ions was monitored. Finally, the organic intermediates identified by chromatographic techniques were used to propose the reaction sequence for the total mineralization of AMT.

Upgrading and expanding the electro-Fenton and related processes

The Fenton-based electrochemical advanced oxidation processes are currently recognized as the most effective technologies to achieve fast and complete degradation of target organic contaminants in water. Electro-Fenton was the pioneering process, but a larger mineralization is attained via UV and solar photoelectro-Fenton processes due to the occurrence of key photoreduction reactions. In practice, the decontamination effectiveness turns out to be limited as solution pH increases and the two-electron oxygen reduction reaction occurring at the cathode becomes inefficient or insufficient. Here, we focus on the current opinion in two crucial features of the reviewed processes: (i) trends in cathodic H 2 O 2 electrogeneration, showing the oxygen reduction reaction upgrading upon use of new and/or more sustainable electrocatalysts, cathode configurations and reactor designs; and (ii) advances in iron-based catalysts, with the main purpose of expanding the application to a much wider pH range, eventually surpassing the classical acidic limitation associated to conventional Fenton's reaction.