Electrochemical Production Of Hydrogen Peroxide Research Articles

Selective Electrochemical H2O2 Production through Two‐Electron Oxygen Electrochemistry

AbstractDirect electrochemical production of hydrogen peroxide (H2O2) through two‐electron oxygen electrochemistry, for example, the oxygen reduction in fuel cells or water oxidation in water electrolyzers, could provide an attractive alternative to locally produce this chemical on demand. The efficiency of these processes depends greatly on the availability of cost‐effective catalysts with high selectivity, activity, and stability. In recent years, various novel nanostructured materials have been reported to selectively produce H2O2. Through combined experimental and theoretical approaches, underlying mechanisms in the electrochemical synthesis of H2O2 via oxygen electrochemistry have been unveiled. Considering the remarkable progress in this area, the authors summarize recent developments regarding the direct production of H2O2 through two‐electron electrochemical oxygen reactions. The fundamental aspects of electrochemical oxygen reactions are first introduced. Various types of catalysts that can effectively produce H2O2 via two‐electron oxygen electrochemistry are then presented. In parallel, the unique structure‐, component‐, and composition‐dependent electrochemical performance together with the underlying catalytic mechanisms are discussed. Finally, a brief conclusion about the recent progress achieved in electrochemical generation of H2O2 and an outlook on future research challenges are given.

Structure, Activity, and Faradaic Efficiency of Nitrogen-Doped Porous Carbon Catalysts for Direct Electrochemical Hydrogen Peroxide Production.

Carbon materials doped with nitrogen are active catalysts for the electrochemical two-electron oxygen reduction reaction (ORR) to hydrogen peroxide. Insights into the individual role of the various chemical nitrogen functionalities in the H2 O2 production, however, have remained scarce. Here, we explore a catalytically very active family of nitrogen-doped porous carbon materials, prepared by direct pyrolysis of ordered mesoporous carbon (CMK-3) with polyethylenimine (PEI). Voltammetric rotating ring-disk analysis in combination with chronoamperometric bulk electrolysis measurements in electrolysis cells demonstrate a pronounced effect of the applied potentials, current densities, and electrolyte pH on the H2 O2 selectivity and absolute production rates. H2 O2 selectivity up to 95.3 % was achieved in acidic environment, whereas the largest H2 O2 production rate of 570.1 mmol g-1 catalyst h-1 was observed in neutral solution. X-ray photoemission spectroscopy (XPS) analysis suggests a key mechanistic role of pyridinic-N in the catalytic process in acid, whereas graphitic-N groups appear to be catalytically active moieties in neutral and alkaline conditions. Our results contribute to the understanding and aid the rational design of efficient carbon-based H2 O2 production catalysts.

Hydroxyl radical generation in electro-Fenton process with in situ electro-chemical production of Fenton reagents by gas-diffusion-electrode cathode and sacrificial iron anode

Hydroxyl radical (·OH) generation in the electro-Fenton process with in situ electro-chemical production of Fenton reagents, i.e. hydrogen peroxide and ferrous ion, by the gas-diffusion-electrode cathode and sacrificial iron anode was systematically investigated. Effects of solution pH and current density (J) on ·OH generation linked strongly with electro-chemical production of hydrogen peroxide at the gas-diffusion-electrode cathode and corrosive production of ferrous ion at sacrificial iron anode were examined. The optimal pH for ·OH generation in the electro-Fenton process was 3 being optimal for the Fenton reaction. The ·OH generation at pH 3 was enhanced with increasing current density and reached the maximum at J=5.8mAcm−2. Further increase in the current density resulted in the retardation of ·OH generation rate. To quantify the ·OH generation, a novel phenomenological reaction kinetic model was developed. The proposed model could quantitatively clarify the ·OH generation in the electro-Fenton process with in situ electro-chemical production of Fenton reagents.

Bifunctional Organic Molecular Electrocatalyst for Hydrogen Evolution Reaction and Hydrogen Peroxide Production

Electrocatalysts are critical for facilitating numerous important electrochemical reactions such as hydrogen evolution reaction (HER) in hydrogen production, oxygen reduction reaction (ORR) in fuel cells,1 and emerging electrochemical production of hydrogen peroxide (H2O2) via a two-electron ORR.2 To date, high-performance electrocatalysts have relied heavily on the use of scarce and expensive precious metals. To lower the cost, researchers have focused on developing platinum group metal-free (PGM-free) electrocatalysts based on earth-abundant elements, such as carbon, nitrogen, and transition metals.3 However, these alternative catalysts often suffer from insufficient stability caused by chemical leaching of transition metal components in harsh acidic environments, which restrict their applications in devices requiring acidic electrolytes, including perfluorosulfonic acids such as Nafion®. In contrast, organic molecules have the advantages of low cost, well-defined active sites and good chemical compatibility with polymer electrolytes. Previous studies have shown the capability of organic molecules to catalyze HER4, 5 and two-electron ORR.6, 7 However, in most cases, these demonstrations were carried out in the electrochemical cell filled with non-aqueous electrolytes and the activities were still very low compared to metal-containing materials. Much work is needed to further improve the activity of organic molecular catalysts, especially in practical polymer electrolyte systems. In this presentation, we will summarize our study of a bifunctional electrocatalyst for HER and two-electron ORR based on a small organic molecule. In rotating disk electrode (RDE) test, the catalyst showed a low onset potential of ca. -0.05 V vs. RHE for HER with an overpotential of ca. -0.35 V at 10 mA/cm2 in 0.5 M H2SO4 at 80 °C. In the MEA-based electrochemical H2 pump test, it reached 10 mA/cm2 at -0.12 V vs. RHE at 80 °C and showed no performance loss in a 60-hour durability test. In addition to the high HER activity, the molecular catalyst also showed high activity and selectivity for two-electron ORR to yield H2O2. The onset potential was ca. 0.6 V vs. RHE with over 80% H2O2 yield in a rotating ring disk electrode (RRDE) test in O2-saturated 0.5 M H2SO4. Density functional theory (DFT) calculations were performed to gain preliminary insight into the reaction mechanisms of HER and two-electron ORR on the organic molecule. The results revealed thermodynamically favorable reaction pathways and structure-activity relationship in this system, which will be presented, too. References Seh, Z. W.; Kibsgaard, J.; Dickens, C. F.; Chorkendorff, I.; Nørskov, J. K.; Jaramillo, T. F. Science 2017, 355, (6321).Siahrostami, S.; Verdaguer-Casadevall, A.; Karamad, M.; Deiana, D.; Malacrida, P.; Wickman, B.; Escudero-Escribano, M.; Paoli, E. A.; Frydendal, R.; Hansen, T. W.; Chorkendorff, I.; Stephens, I. E. L.; Rossmeisl, J. Nat Mater 2013, 12, (12), 1137-1143.Hu, C.; Dai, L. Angew. Chem. Int. Ed. 2016, 55, (39), 11736-11758.Cretu, R.; Kellenberger, A.; Medeleanu, M.; Vaszilcsin, N. Int. J. Electrochem. Sci. 2014, 9, (8), 4465-4477.Uchida, T.; Mogami, H.; Yamakata, A.; Sasaki, Y.; Osawa, M. J. Am. Chem. Soc. 2008, 130, (33), 10862-10863.Trojanek, A.; Langmaier, J.; Sebera, J.; Zalis, S.; Barbe, J.-M.; Girault, H. H.; Samec, Z. Chem. Commun. 2011, 47, (19), 5446-5448.Hatay, I.; Su, B.; Méndez, M. A.; Corminboeuf, C.; Khoury, T.; Gros, C. P.; Bourdillon, M.; Meyer, M.; Barbe, J.-M.; Ersoz, M.; Záliš, S.; Samec, Z.; Girault, H. H. J. Am. Chem. Soc. 2010, 132, (39), 13733-13741.

Electrochemical Synthesis of H2O2 Via Water Electrolysis

Hydrogen peroxide (H2O2) is a crucial chemical with a wide range of applications in various industries, including paper bleaching, textile manufacturing and environmental protection for distillation, detoxification and color removal of wastewater. Electrochemical production of hydrogen peroxide (H2O2) offers small scale decentralized process which is highly desirable for remote usages. Both oxygen reduction (eq. 1) and water oxidation (eq. 2) reactions could be exploited to produce H2O2.O2 + 2(H++e-) ---> H2O2 E0 = 0.7 V (1)2H2O ---> 2(H++e-) + H2O2 E0 = 1.76 V (2)These reactions are simple and remarkable, but in practice selectivity toward the desired H2O2 product is an issue since these are not the thermodynamically favored reactions for oxygen reduction and water oxidation. Over the past years, several efforts have been made to find selective, and active catalysts for these reactions.1–4 In this work, by combining density functional theory (DFT) calculations and experiment, we provide leads to design suitable electrocatalysts with high selectivity and activity for H2O2 synthesis from both processes.3 References (1) Siahrostami, S.; Verdaguer-Casadevall, A.; Karamad, M.; Deiana, D.; Malacrida, P.; Wickman, B.; Escudero-Escribano, M.; Paoli, E. a; Frydendal, R.; Hansen, T. W.; Chorkendorff, I.; Stephens, I. E. L. S.; Stephens, I. E.; Rossmeisl, J. Nat. Mater. 2013, 12 (12), 1137–1143.(2) Verdaguer-Casadevall, A.; Deiana, D.; Karamad, M.; Siahrostami, S.; Malacrida, P.; Hansen, T. W.; Rossmeisl, J.; Chorkendorff, I.; Stephens, I. E. L. Nano Lett. 2014, 14 (3), 1603–1608.(3) Siahrostami, S.; Li, G.-L.; Viswanathan, V.; Nørskov, J. K. J. Phys. Chem. Lett. 2017, 1157–1160.(4) Shi, X.; Siahrostami, S.; Li, G.-L.; Zhang, Y.; Chakthranont, P.; Studt, F.; Jaramillo, T. F.; Zheng, X.; Nørskov, J. K. Nat. Commun. 2017 (SEPT), 1–12.

Carbon catalysts for electrochemical hydrogen peroxide production in acidic media

Hydrogen peroxide is a commodity chemical, as it is an environmentally friendly oxidant. The electrochemical production of H2O2 from oxygen and water by the reduction of oxygen is of great interest, as it would allow the decentralized, on-site, production of pure H2O2. The ability to run the reaction in an acidic electrolyte with high performance is particularly important, as it would allow the use of polymer solid electrolytes and the production of pH-neutral hydrogen peroxide. Carbon catalysts, which are cheap, abundant, durable and can be highly selective show promise as potential catalysts for such systems. In this work, we examine the electrocatalytic performance and properties of seven commercially available carbon materials for H2O2 production by oxygen electroreduction. We show that the faradaic efficiencies for the reaction lie in a wide range of 18–82% for different carbon catalysts. In order to determine the cause of these differences, we employ prompt gamma ray/neutron activation analysis and XPS measurements to assess the contribution of heteroatoms and defects, as well as low temperature N2-adsorption and transmission electron microscopy to elucidate the particle size, shape, BET surface area and porosity. We find that the surface oxygen groups, nitrogen and sulphur content display effects that are not straightforward, because their chemical state is likely significant. The metal content (when present in the order of magnitude of ∼10 ppm) is not a straightforward indicator of the electrocatalytic performance for this reaction. XPS and BET data indicate that carbons displaying high selectivities for the 2-electron process contain more aliphatic-like, “defect” structures on the surface.

Electrochemical Hydrogen Peroxide Production in Acidic Medium Using a Tubular Photo-reactor: Application in Advanced Oxidation Processes

This paper describes the results obtained in the design and characterization of a tubular electrochemical reactor. The set-up was employed for on-site hydrogen peroxide (H2O2) production in an acidic medium (pH 3) to promote three electrochemical advanced oxidation processes (EAOP): electro-Fenton (EF), photoelectro-Fenton (PEF) and photocatalysis treatment (PT). These processes were evaluated by their abilities to degrade a commercial dye, Orange-II (OGII), in solution using total organic carbon (TOC) removal and high performance liquid chromatography (HPLC). To have free solutions of iron in the EF and PEF systems, a NafionTM membrane with dispersed iron was prepared. For use in photocatalysis, electrodes with a large superficial area were prepared by coating carbon cloth fiber supports with titanium dioxide (TiO2) using the electrophoretic (EP) method. In this work, wastewater samples with a large number of microorganisms (coliform bacteria) were treated with this new reactor design.

Understanding activity trends in electrochemical water oxidation to form hydrogen peroxide

Electrochemical production of hydrogen peroxide (H2O2) from water oxidation could provide a very attractive route to locally produce a chemically valuable product from an abundant resource. Herein using density functional theory calculations, we predict trends in activity for water oxidation towards H2O2 evolution on four different metal oxides, i.e., WO3, SnO2, TiO2 and BiVO4. The density functional theory predicted trend for H2O2 evolution is further confirmed by our experimental measurements. Moreover, we identify that BiVO4 has the best H2O2 generation amount of those oxides and can achieve a Faraday efficiency of about 98% for H2O2 production.

Effect of rf-Plasma Treatment on the Activity and Selectivity of Me-N-C Electrocatalysts for the Oxygen Reduction Reaction

In view of the transfer from fossil fuels to renewable energies, electrochemical reactions offer the chance of a fast and environmentally friendly production of chemicals or the transfer of chemical energy into electric energy (e.g. via fuel cells). While Me-N-C catalysts are already well-established as promising alternative to Pt/C in fuel cell applications [1], some of them might also be of interest for the electrochemical production of H2O2 (hydrogenperoxide) as an intermediate product.[2, 3] So far the largest efforts in electrochemical production of hydrogen peroxide are made by using supported metal (e.g. Pd, Au-Pd, Pd-Hg) nanoparticles [4, 5] and nitrogen coordinated metal complexes [6, 7] but recently also non-precious MNC catalysts have attracted attention due to their high ORR activity.[7-9] In a previous publication we have shown that the presence of protonated nitrogen groups can enhance the ORR activity of Fe-N-C catalysts.[10] In addition theoretical calculations reveal that the largest enhancement in terms of required overpotential would be expected for the combination of MnN4 sites with carboxylic group.[11] In this work, we try to apply this promotor concept to our MNC catalysts (M= Co, Fe, Mn) by introducing targeted carboxylic groups via plasma treatments in different gas atmospheres (O2, CO2). Fe-N-C was selected as most promising candidate for FC application, Co-N-C as possible candidate for hydrogen peroxide formation and Mn-N-C due to previous findings on the improvement of the overpotential by carboxylic groups.[11] Rotating ring disk (RRDE) studies were performed to investigate the positive effect of plasma treatments on the activity and selectivity of the MNC catalysts. In addition, the initial and the modified MNCs were characterized using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy to identify the plasma induced structural changes and their effect on the activity and selectivity data.

Organic Molecular Catalyst for Electrochemical Production of Hydrogen Peroxide

Hydrogen peroxide (H2O2) as a low cost, safe and clean disinfection agent plays an important role in providing clean water for human society. Compared with complicated industrial anthraquinone process or direct catalytic synthesis from H2 and O2, the distributed production of H2O2 in a polymer electrolyte fuel cell system (PEFC) has numerous merits, including lower financial and energy cost, safer process, use of small-scale, easily deployable device.1,2 For these reasons, there is strong interest in developing electrocatalysts with high activity and selectivity for H2O2 production via the electrochemical reduction of molecular oxygen. Up until now, H2O2 electrocatalysts have been based on precious-metal amalgams, which are costly, scarce, and difficult to handle safely due to the use of Hg.2,3 Carbon-based electrocatalysts have been considered for H2O2 production,4-6 as have been metal-free and nitrogen-containing molecular catalysts known to be selective for two-electron reduction of O2 in various media.7-9 In this presentation, we will demonstrate a new catalyst based on a small organic molecule that enables electrochemical production of H2O2 in an aqueous acidic electrolyte (0.5 M H2SO4). When adsorbed onto glassy carbon this molecular catalyst shows a high onset potential of around 0.6 V vs. RHE, and a specific current density > 1.3 mA/cm2 ECA at 0 V vs. RHE in electrochemical cell test. Rotating ring-disk electrode (RRDE) studies indicate high selectivity for H2O2 production, with H2O2 yield over 80%, and current efficiency over 67%. The durability of this molecule has been evaluated in an electrochemical cell, as well as in a PEFC. Based on experimental data and density functional theory (DFT) calculations, a two electron oxygen reduction mechanism on this molecular catalyst will be proposed. References (1) Centi, G.; Perathoner, S.; Abate, S. In Modern Heterogeneous Oxidation Catalysis; Wiley-VCH Verlag GmbH & Co. KGaA: 2009, p 253. (2) Siahrostami, S.; Verdaguer-Casadevall, A.; Karamad, M.; Deiana, D.; Malacrida, P.; Wickman, B.; Escudero-Escribano, M.; Paoli, E. A.; Frydendal, R.; Hansen, T. W.; Chorkendorff, I.; Stephens, I. E. L.; Rossmeisl, J. Nat. Mater. 2013, 12, 1137. (3) Verdaguer-Casadevall, A.; Deiana, D.; Karamad, M.; Siahrostami, S.; Malacrida, P.; Hansen, T. W.; Rossmeisl, J.; Chorkendorff, I.; Stephens, I. E. L. Nano Lett. 2014, 14, 1603. (4) Yamanaka, I.; Onizawa, T.; Takenaka, S.; Otsuka, K. Angew. Chem. Int. Ed. 2003, 42, 3653. (5) Yamanaka, I.; Onisawa, T.; Hashimoto, T.; Murayama, T. ChemSusChem 2011, 4, 494. (6) Fellinger, T.-P.; Hasché, F.; Strasser, P.; Antonietti, M. J. Am. Chem. Soc. 2012, 134, 4072. (7) Hatay, I.; Su, B.; Méndez, M. A.; Corminboeuf, C.; Khoury, T.; Gros, C. P.; Bourdillon, M.; Meyer, M.; Barbe, J.-M.; Ersoz, M.; Záliš, S.; Samec, Z.; Girault, H. H. J. Am. Chem. Soc. 2010, 132, 13733. (8) Wu, S.; Su, B. Chem. Eur. J. 2012, 18, 3169. (9) Savéant, J.-M. Chem. Rev. 2008, 108, 2348.

A biomass derived N/C-catalyst for the electrochemical production of hydrogen peroxide.

Pomelo peel, a waste biomass, was used as an all-in-one (carbon source, self-template, and heteroatom) precursor to develop a nanoporous N/C-electrocatalyst for highly selective and energy-saving H2O2 production, in which disordered carbonous defects and five-membered rings (pyrrolic-N) played vital roles.

Quantitative Kinetic Analysis of a PdAu3 Alloy Catalyst for Oxygen Electro-Reduction

The oxygen reduction reaction (ORR) mechanism for electrochemical production of hydrogen peroxide is investigated for an Au-Pd catalyst with 25 at% palladium. The sample was prepared by chemical reduction of a precursor solution on a carbon-based substrate. Rotating ring-disk electrode (RRDE) measurements were performed for electrochemical characterization exhibiting H2O2 current efficiencies of about 75-78% at low disk potentials. The focus of this article is on the mathematical evaluation of the experimental data using the analytical method from Damjanovic et al. [J. Chem. Phys. 45, 4057 (1966)] and a powerful numerical data fitting technique based on RRDE simulations in MATLAB, which is capable of investigating reaction mechanisms with different structures. The latter method is presented in detail and the electro-kinetic parameters of the ORR mechanism at the considered catalyst resulting from both methods are compared quantitatively. It is found that the oxygen reductions via the 2-electron and the 4-electron pathways occur in parallel, whereas the hydrogen peroxide reduction pathway is found apparently inactive.

Influence of Different Operating Parameters on the Partial Reduction of Oxygen for Hydrogen Peroxide Production

Hydrogen peroxide has gained increasing importance as green oxidiser in a number of chemical and other processes. This includes processes performed in smaller scale local facilities. In order to maintain a low environmental food print a local production is to be preferred. Thereby it would be particularly beneficial if the process could make use of excess renewable electricity. This is why the electrochemical production of hydrogen peroxide has recently attracted increasing interest. An energy efficient option for the electrochemical hydrogen peroxide production is by the partial reduction of oxygen. The challenge is to obtain a high hydrogen peroxide current efficiency (HPCE). Beside the possible parallel complete reduction of oxygen to water the subsequent electrochemical reduction of H2O2 to water and the heterogeneously catalysed disproportionation of H2O2 into water and oxygen are reactions which can reduce the HPCE. In this study different factors influencing the HPCE were studied. All tests were done using a rotating ring disk electrode set-up from PINE instruments. In all tests a platinum ring electrode set to a potential of 1.2 V vs. reversible hydrogen electrode (RHE) was used to detect the hydrogen peroxide leaving the disk working electrode. The reduction of potassium ferricyanide K3[Fe(CN)6] to potassium ferrocyanide K4[Fe(CN)6] at the disk electrode and the reversed oxidation of the formed K4[Fe(CN)6] at the ring electrode were used to calibrate the capture efficiency of the RRDE tip before each experiment. For a first set of experiments a polycrystalline platinum disk electrode was used as working electrode to study the effects of reaction conditions like temperature and pH on the HPCE. The effect of the rotation speed on the HPCE was used as indicator for the reduction of the HPCE by subsequent decomposition of the primary formed hydrogen peroxide via a further reduction step or disproportionation at the disk electrode. An increase of the HPCE with increasing rotation speed is expected if the subsequent decomposition of H2O2 is significant because the mass transport for the removal of formed H2O2 out of the reaction zone gets enhanced. Further tests were made by applying different supported catalyst onto a glassy carbon disk electrode to investigate the effect of the chemical composition of the electrode on the HPCE. Catalysts investigated were gold on carbon Au/C and palladium gold alloy on carbon PdAu/C. For the tests at the platinum electrode the trends known from literature could be confirmed. In an acidic environment (0.1 M HClO4) the hydrogen peroxide production could be strongly increased by reducing the cell temperature from 25 °C to 10 °C in accordance with the findings of Yamanaka (1). It also was found that the hydrogen peroxide production is strongly increased with rotating speed indicating that subsequent H2O2 decomposition proceeds fast at the platinum disk electrode in accordance with the findings of Seidel et al. (2). If the reaction is conducted in an alkaline environment (0.1 M KOH) similar trends with respect to the effect of temperature and rotating speed were observed. The major effect of the increased pH was that the onset of the H2O2 formation was observed at significant higher potentials than under acidic conditions and that high H2O2 production rates were achieved at much lower over potentials (cf. fig 1). With a carbon supported gold catalyst higher H2O2 –concentrations were achieved in the alkaline environment, though at slightly higher over potentials than for the Pt disk electrode. The H2O2 production is almost independent of the rotation speed and is higher at 25 °C than at 10 °C. This indicates that the gold catalyst does not catalyse the decomposition of H2O2. Under acidic conditions the oxygen reduction activity as well as the H2O2 formation rate are both strongly reduced and occur only at very significant over potential (cf. fig 2) By alloying the gold catalyst with palladium an enhancement of the catalytic performance in the acidic environment was achieved even at ambient temperature (cf. fig 3). As the acidic environment is more beneficial to the downstream processing of the H2O2 PdAu/C is currently the most suitable catalyst. In the contribution further tests on the effect of the kind of acid and of H2O2 stabilisation with phosphoric acid additions will be reported. The support of this work by the Fraunhofer-Gesellschaft as part of the project “Current as Raw Material” contract 007-600830 is gratefully acknowledged.

Hydrogen Peroxide Synthesis via Enhanced Two-Electron Oxygen Reduction Pathway on Carbon-Coated Pt Surface

Continuous on-site electrochemical production of hydrogen peroxide (H2O2) can provide an attractive alternative to the present anthraquinone-based H2O2 production technology. A major challenge in the electrocatalyst design for H2O2 production is that O2 adsorption on the Pt surface thermodynamically favors “side-on” configuration over “end-on” configuration, which leads to a dissociation of O–O bond via dominant 4-electron pathway. This prefers H2O production rather than H2O2 production during the electrochemical oxygen reduction reaction (ORR). In the present work, we demonstrate that controlled coating of Pt catalysts with amorphous carbon layers can induce selective end-on adsorption of O2 on the Pt surface by eliminating accessible Pt ensemble sites, which allows significantly enhanced H2O2 production selectivity in the ORR. Experimental results and theoretical modeling reveal that 4-electron pathway is strongly suppressed in the course of ORR due to a thermodynamically unfavored end-on adsorption of O2 (the first electron transfer step) with 0.54 V overpotential. As a result, the carbon-coated Pt catalysts show an onset potential of ∼0.7 V for ORR and remarkably enhanced H2O2 selectivity up to 41%. Notably, the produced H2O2 cannot access the Pt surface due to the steric hindrance of the coated carbon layers, and thus no significant H2O2 decomposition via disproportionation/reduction reactions is observed. Furthermore, the catalyst shows superior stability without considerable performance degradation because the amorphous carbon layers protect Pt catalysts against the leaching and ripening in acidic operating conditions.

Electrochemical Pre-Oxidation of Drinking Water by On-Site Electro-Generation of Hydrogen Peroxide

Hydrogen peroxide is a green oxidizer. On-site electrochemical production of hydrogen peroxide has potential to become a new way for raw water pre-oxidation. The performance of electro-generation hydrogen peroxide was studied in the electrochemical reactor equipped with graphite felt as cathode and RuO2-IrO2-coated titanium mesh as anode. The effect of water flow rate, air flow rate and current density on concentration of hydrogen peroxide and energy consumption was studied. Results indicate that the optimal condition for the lowest energy consumption is to directly produce 5 mg/L of hydrogen peroxide as compared with producing high concentration followed by dilution. It was found that electrochemical pre-oxidation technology had a good effect on sterilization and removing turbidity and stink for raw water.

Electrogeneration Of H2O2 in Acid Medium Using Catalysts Modified with Manganese II Phthalocyanine Supported in Printex 6L Carbon

The electrochemical production of hydrogen peroxide by the oxygen reduction reaction (ORR) is becoming a viable alternative as generation takes place in situ, eliminating any problems of transport and storage. In this paper, we have studied the basis of manganese II phthalocyanine (Ph-Mn) catalysts supported in Printex 6L carbon, in order to increase the generation efficiency of H2O2. The results showed that with the catalyst containing 1.0% of Ph-Mn there was an increase in H2O2 production efficiency of 82% in comparison to 80% obtained for unmodified Printex 6L. However, it was observed that the greater the amount of Ph-Mn incorporated into the catalyst, the lower the tendency for the reaction formation of H2O2

Modification of carbon electrodes for oxygen reduction and hydrogen peroxide formation: The search for stable and efficient sonoelectrocatalysts

We report on the use of glassy carbon electrodes modified with 9,10-phenanthraquinone or 1,2-naphthoquinone for their applicability as catalytic materials for oxygen reduction and hydrogen peroxide producers. The stability of these modified electrodes are investigated and found to be suitable for use under ultrasound, so providing a basis for the electrochemical production of hydrogen peroxide.

Surface redox catalysis for O 2 reduction on quinone-modified glassy carbon electrodes

The electrochemical reduction of oxygen on bare glassy carbon (GC) and on electrodes grafted with anthraquinone has been studied using the rotating ring-disk electrode (RRDE) technique. The electrode surface was grafted by the electrochemical reduction of the corresponding diazonium salt. The functionalised electrode showed quasi-reversible redox behaviour in oxygen-free 0.1 M KOH and the cyclic voltammetric response of the surface bound anthraquinone was stable on potential cycling. The covalently attached anthraquinone acts as an electrocatalyst for oxygen reduction and a well defined diffusion limited current plateau was observed in the potential range from −0.75 to −1.25 V (SCE) in 0.1 M KOH. The RRDE results show that oxygen reduction on both electrode surfaces studied stops at the hydrogen peroxide stage. The modified carbon electrodes are potential candidates for the electrochemical production of hydrogen peroxide.

Oxygen-utilization Performance of Trickle-bed Cathode for On-site Electrochemical Production of Hydrogen Peroxide

Oxygen-utilization Performance of Trickle-bed Cathode for On-site Electrochemical Production of Hydrogen Peroxide

Effect of Flow Mode of Gas-Liquid Phase in Graphite-Felt Cathode on Electrochemical Production of Hydrogen Peroxide.

An electrochemical reactor has been developed for the on-site electrochemical production of hydrogen peroxide. Comparison was made between a trickle-bed mode where gas and liquid phases flowed downward cocurrently in the graphite-felt cathode and a packed-bed mode where two phases flowed upward cocurrently. At the same flow condition of gas-liquid phase, the current efficiency Ce using the trickle-bed electrode was higher than that using the packed-bed electrode with gas-sparging. Mathematical analysis based on a three-phase bed model was made to fit the over-potential profiles in the cathode by using electrode kinetics and mass-transfer parameters, gas and liquid holdups in the bed, the effective conductivity of the solution phase and the effective surface area of electrode. The current efficiency Ce was affected by flow rates of gas and liquid, and the current density, because of the changes in the effective specific surface area aeff of electrode and liquid-solid mass transfer coefficient kmA of oxygen onto the electrode. In this experiment, Ce was increased mainly by increasing aeff rather than kmA. Using the trickle-bed electrode, aeff and kmA were higher than that using the packed-bed electrode, because oxygen gas and catholyte were dispersed uniformly in the cathode compartment, thus leading to higher Ce.