Electrochemical Production Of Hydrogen Peroxide Research Articles

Efficient electrochemical hydrogen peroxide production enabled by defect engineering of epoxy-rich carbon materials

Efficient electrochemical hydrogen peroxide production enabled by defect engineering of epoxy-rich carbon materials

Local pH Gradients Alter Product Selectivity of Electrocatalytic Oxygen Reduction Reaction on La‐Cr‐Co Perovskites

The electrochemical production of hydrogen peroxide through the oxygen reduction reaction (ORR) presents the interesting situation where the fully reduced form, H2O, is significantly favored by thermodynamics.Perovskite oxide based catalysts with slow kinetics, or large overpotentials, have been shown to enable production of H2O2 with good selectivity, but this comes at the expense of energy efficiency and production rates. We analyze the structure and electrocatalytic ORR capabilities of a perovskite oxide series based on LaCr1‐xCoxO3. We find that the crystal lattice distorts in two ways as Co content increases – anisotropic compression of the lattice is accompanied by a pinching of angles within the structure, which gives way to compression of B‐O bonds at higher Co contents. Product selectivity is observed to change as a function of both catalyst composition and rotation rates of rotating ring‐disk electrode. The rotation‐dependent behavior is attributed to accelerated displacement of surface‐bound peroxide intermediates by a pH gradient at the catalyst surface, and composition‐dependent changes in selectivity are found to correlate to the angular distortion of the crystal lattice. These results highlight the importance of local environments in electrocatalyst reactions and demonstrate that structure and local pH can be used to manipulate product selectivity.

Electrochemical H2O2 Production Modelling for an Electrochemical Bandage

Hydrogen peroxide (H2O2) is an environmentally friendly oxidizing agent used to treat wound infections. We have developed an electrochemical bandage (e-bandage), which generates H2O2 in situ and shown that it exhibites in vitro and in vivo efficacy. The electrochemical bandage comprises carbon fabric working and counter electrodes, as well as an Ag/AgCl quasi-reference electrode, separated by cotton fabric and the electrolyte is delivered by Xanthan gum with phosphate buffer saline. While the chemistry and electrochemistry of the e-bandage have been experimentally characterized, the system level description could aid in better designing these devices. Here, a model called electrochemical hydrogen peroxide production (EHPP) was used to evaluate factors influencing electrochemical generation of H2O2, including electrode potential, diffusion and reaction rates, temperature, and various geometries. EHPP model parameters estimated based on experimental results indicate that: (i) with diffusion limitations caused by changes in physical conditions (e.g., drying of hydrogel), the rate of H2O2 generation decreases, (ii) higher working electrode overpotentials increase H2O2 generation and higher counter electrode overpotentials do not affect H2O2 generation, (iii) increasing the distance between electrodes by adding more hydrogel reduces H2O2 generation, (iv) net H2O2 generation decreases ∼12% with temperature, and (v) H2O2 production is most effective in the initial 48 h of operation.

Structural Modulation of Covalent Organic Frameworks for Efficient Hydrogen Peroxide Electrocatalysis.

The electrochemical production of hydrogen peroxide (H2O2) using metal-free catalysts has emerged as a viable and sustainable alternative to the conventional anthraquinone process. However, the precise architectural design of these electrocatalysts poses a significant challenge, requiring intricate structural engineering to optimize electron transfer during the oxygen reduction reaction (ORR). Herein, we introduce a novel design of covalent organic frameworks (COFs) that effectively shift the ORR from a four-electron to a more advantageous two-electron pathway. Notably, the JUC-660 COF, with strategically charge-modified benzyl moieties, achieved a continuous high H2O2 yield of over 1200 mmol g-1 h-1 for an impressive duration of over 85 hours in a flow cell setting, marking it as one of the most efficient metal-free and non-pyrolyzed H2O2 electrocatalysts reported to date. Theoretical computations alongside in situ infrared spectroscopy indicate that JUC-660 markedly diminishes the adsorption of the OOH* intermediate, thereby steering the ORR towards the desired pathway. Furthermore, the versatility of JUC-660 was demonstrated through its application in the electro-Fenton reaction, where it efficiently and rapidly removed aqueous contaminants. This work delineates a pioneering approach to altering the ORR pathway, ultimately paving the way for the development of highly effective metal-free H2O2 electrocatalysts.

Structural Modulation of Covalent Organic Frameworks for Efficient Hydrogen Peroxide Electrocatalysis

The electrochemical production of hydrogen peroxide (H2O2) using metal‐free catalysts has emerged as a viable and sustainable alternative to the conventional anthraquinone process. However, the precise architectural design of these electrocatalysts poses a significant challenge, requiring intricate structural engineering to optimize electron transfer during the oxygen reduction reaction (ORR). Herein, we introduce a novel design of covalent organic frameworks (COFs) that effectively shift the ORR from a four‐electron to a more advantageous two‐electron pathway. Notably, the JUC‐660 COF, with strategically charge‐modified benzyl moieties, achieved a continuous high H2O2 yield of over 1200 mmol g‐1 h‐1 for an impressive duration of over 85 hours in a flow cell setting, marking it as one of the most efficient metal‐free and non‐pyrolyzed H2O2 electrocatalysts reported to date. Theoretical computations alongside in‐situ infrared spectroscopy indicate that JUC‐660 markedly diminishes the adsorption of the OOH* intermediate, thereby steering the ORR towards the desired pathway. Furthermore, the versatility of JUC‐660 was demonstrated through its application in the electro‐Fenton reaction, where it efficiently and rapidly removed aqueous contaminants. This work delineates a pioneering approach to altering the ORR pathway, ultimately paving the way for the development of highly effective metal‐free H2O2 electrocatalysts.

Electrogenerated chemiluminescence from luminol-labelled microbeads triggered by in situ generation of hydrogen peroxide.

We developed a sensing strategy that mimics the bead-based electrogenerated chemiluminescence immunoassay. However, instead of the most common metal complexes, such as Ru or Ir, the luminophore is luminol. The electrogenerated chemiluminescence of luminol was promoted by in situ electrochemical generation of hydrogen peroxide at a boron-doped diamond electrode. The electrochemical production of hydrogen peroxide was achieved in a carbonate solution by an oxidation reaction, while at the same time, microbeads labelled with luminol were deposited on the electrode surface. For the first time, we proved that was possible to obtain light emission from luminol without its direct oxidation at the electrode. This new emission mechanism is obtained at higher potentials than the usual luminol electrogenerated chemiluminescence at 0.3-0.5V, in conjunction with hydrogen peroxide production on boron-doped diamond at around 2-2.5V (vs Ag/AgCl).

Enhanced electroproduction of hydrogen peroxide with oxidized boron-doped carbon catalysts synthesized from gaseous CO2

As an eco-friendly alternative to the conventional anthraquinone process, electrochemical production of hydrogen peroxide (H2O2) through the oxygen reduction reaction has been attracting attention. The goal of this work is to derive a carbon-based material from carbon dioxide (CO2) to achieve high performance in electrochemical H2O2 production. Doping heterogeneous element such as oxygen on a carbon catalyst has been mainly explored to increase the selectivity and activity, but little research has been conducted on enhancing catalytic activity with oxidized boron insertion. This study proposes porous carbon materials synthesized from CO2 as electrocatalysts. Polyethylene oxide (PEO) was thermally treated together to increase the boron-oxygen bonding sites. As a result, the synthesized carbon materials having oxidized boron functional groups of BC2O and BCO2 showed high activity (1.25 mA cm−2) and selectivity (∼90 %) over a wide voltage range in two-electron ORR (Oxygen Reduction Reaction) at alkaline media. Furthermore, in an H-cell where 0.4 V vs. RHE was applied, the average H2O2 production rate was maintained at 452.96 mmol g−1 h−1 for four hours with a high faraday efficiency of 90 %.

Trans-electrode pressure of gas-diffusion electrodes significantly influencing the electrochemical hydrogen peroxide production

Hydrogen peroxide (H2O2) synthesis by electrochemical two-electron oxygen reduction has garnered increasing interest as a wide range of potential applications. Gas diffusion electrodes (GDEs) can effectively promote the H2O2 production efficiency by overcoming the oxygen mass transfer limitations but strongly influenced by the electrowetting process along the long-term operation. In this study, the effect of trans-electrode pressure (TEP) of GDE cathode on the electrowetting process was further elucidated. We controlled the TEP values of four types of GDEs: two Ni-based GDEs and two carbon cloth GDEs prepared by hot-pressing or brushing carbon black. SBA-15 was further used to regulate the microstructure of one Ni-based GDE. It was found that an optimal range of TEP occurred for all tested GDEs in terms of the max. concentration, the yield efficiency, the energy consumption, and the stability because TEP may change the triple-phase interface and influence the anti-electrowetting effect. The porosity of hot-pressed Ni GDE can maintain the TEP window and thus enhance the production of H2O2, likely via creating oxygen-containing functional groups and a bimodal pore structure on the electrode, revealed with several characterization techniques including SEM, CA, XPS, Raman spectra, CV and EIS. The porous Ni GDE presented an efficient and stable production of H2O2 for 10 cycles: yielding H2O2 at 4393.2–4602.2 mmol m−2 h−1 with current efficiencies of 94.2–98.7%. The best accumulated H2O2 concentration can reach up to 3.58 ωt% H2O2 at 10 h. The results provide an important reference for the industrial scaleup of electro-production of H2O2 with GDEs.

Revealing the origin of single‐atom W activity in H2O2 electrocatalytic production: Charge symmetry‐breaking

AbstractThe low‐energy electrochemical production of hydrogen peroxide (H2O2) has garnered significant attention as a viable alternative to traditional industrial routes, with the goal of achieving carbon neutrality. For their H2O2 selectivity in the two‐electron oxygen reduction reaction (ORR), the coordination environment of tungsten (W)‐based materials is critical. In this study, atomically dispersed W single atoms were immobilized on N‐doped carbon substrates by a facile pyrolysis method to obtain a W single‐atom catalyst (W‐SAC). The coordination environment of an isolated W single atom with a tetra‐coordinated porphyrin‐like structure in W‐SAC was determined by X‐ray photoelectron spectroscopy and X‐ray absorption spectroscopy analysis. Notably, the as‐prepared W‐SAC showed superior two‐electron ORR activity in 0.1 M KOH solution, including high onset potential (0.89 V), high H2O2 selectivity (82.5%), and excellent stability. By using differential phase contrast‐scanning transmission electron microscopy and density functional theory calculations, it is revealed that the charge symmetry‐breaking of W atoms changes the adsorption behavior of the intermediates, leading to enhanced reactivity and selectivity for two‐electron ORR. This work broadens the avenue for understanding the charge transfer of W‐based electrocatalytic materials and the in‐depth reaction mechanism of SACs in two‐electron ORR.

Innovative carbon materials from lignocellulosic wastes for electrochemical hydrogen peroxide production: Bridging biomass conversion and material properties

This study aims to assess the electrochemical generation of hydrogen peroxide and hydroxyl radicals (*OH) using carbon cathodes synthesized from three different lignocellulosic residues, Phragmites australis (PA), Cladium mariscus (CM) and Typha domingensis (TD). These vegetal species are commonly used in natural wetlands and phytoremediation processes and can accumulate recalcitrant pollutants within these treatment processes, generating a waste that should be properly managed. To convert these residues into valuable carbon materials, they underwent hydrothermal carbonization (HTC) followed by either chemical activation with KOH or pyrolysis at 1000 ºC. The best results were obtained with chemically activated materials, yielding a maximum H2O2 concentration of 313 mg L−1 with the carbon cathode produced from PA. The specific surface area, oxygenated functional groups and presence of structural defects in carbonous structures, were key parameters related to a good performance as catalysts towards the 2e- Oxygen Reduction Reaction (ORR). It was also demonstrated, in comparison with previous studies, that the presence of heavy metals in the structure of the lignocellulosic residue enhanced the decomposition of H2O2 into *OH. However, in the study of the degradation of a model organic contaminant as methylene blue (MB), it was shown that these *OH were not the main contributors to degradation, as direct H2O2 chemical degradation and adsorption on the carbon materials played the most significant role. Therefore, the outstanding capacity of these lignocellulosic residues as catalysts for the electrogeneration of H2O2 was confirmed, suggesting their potential future application in advanced oxidation processes for water decontamination.

Isomerization Engineering of Oxygen-Enriched Carbon Quantum Dots for Efficient Electrochemical Hydrogen Peroxide Production.

Hydrogen peroxide (H2O2) has emerged as a kind of multi-functional green oxidants with extensive industrial utility. Oxidized carbon materials exhibit promises as electrocatalysts in the two-electron (2e-) oxygen reduction reaction (ORR) for H2O2 production. However, the precise identification and fabrication of active sites that selectively yield H2O2 present a serious challenge. Herein, a structural engineering strategy is employed to synthesize oxygen-doped carbon quantum dots (o-CQD) for the 2e- ORR. The surface electronic structure of the o-CQDs is systematically modulated by varying isomerization precursors, thereby demonstrating excellent electrocatalyst performance. Notably, o-CQD-3 emerges as the most promising candidate, showcasing a remarkable H2O2 selectivity of 96.2% (n = 2.07) at 0.68V versus RHE, coupled with a low Tafel diagram of 66.95mV dec-1. In the flow cell configuration, o-CQD-3 achieves a H2O2 productivity of 338.7mmol gcatalyst -1 h-1, maintaining consistent production stability over an impressive 120-hour duration. Utilizing in situ technology and density functional theory calculations, it is unveil that edge sites of o-CQD-3 are facilely functionalized by C-O-C groups under alkaline ORR conditions. This isomerization engineering approach advances the forefront of sustainable catalysis and provides a profound insight into the carbon-based catalyst design for environmental-friendly chemical synthesis processes.

Catalyst-less efficient electrochemical production of hydrogen peroxide

Hydrogen peroxide is produced efficiently in a catalyst-less electrochemical cell manufactured at lab scale (4 cm2 of electrode size) by resin and titanium 3-D printing. The electrolyte inlet and outlet of the cell are designed to promote a very turbulent flow pattern that provides good mixing of the liquid and gas phases and minimizes the mass transport limitations. The mechanization of the titanium contributes to an efficient gas diffusion in the cathode which was successfully adapted to the 3-D printed cell resulting in a very efficient gas–liquid reactive absorbent unit. The effect of the electrolyte, operation mode, gas and liquid flow rates were evaluated on the electrochemical production of hydrogen peroxide and the results obtained were successfully fitted to a simple phenomenological model that helped to obtain a deep understanding of the process. The proposed electrochemical gas–liquid absorber achieved coulombic efficiencies as high as 69.72 % and energy consumptions close to 9 mg H2O2 (Wh)−1 when the system was operated in continuous mode with the most efficient conditions (no cell compartmentation and feeding pure oxygen with electrolytes containing sulphate salts at pH near 3). Those values of efficiencies are in the upper range of the results found in the literature for the electrochemical production of hydrogen peroxide, even though no catalytic coating was used to promote this cathodic reaction. An unexpected effect of the salt contained in the electrolyte was observed indicating the existence of other production mechanisms that require further characterization.

Magnetic field-enhanced oxygen reduction reaction for electrochemical hydrogen peroxide production with different cerium oxide nanostructures

We investigated cerium oxide nanoparticles of various morphologies (nanosheets, nanocubes, and nanoparticles) supported on carbon Vulcan XC-72 for the two-electron oxygen reduction reaction (ORR). A continuous magnetic field (2000 Oe) was used for the first time in the literature. The best results were for 5 % (w/w) CeO2 for all three different morphologies, more than doubling the ring current, enhancing the hydrogen peroxide selectivity from 51 % (Vulcan XC-72) to 84–89 %, and modifying the onset potential to lesser negative values. The presence of the magnetic field led to even higher ring currents with 5 % (w/w) CeO2, H2O2 selectivity from 54 % (Vulcan XC-72) to 88–96 % and changing even more the onset potential. Those results were correlated with the Zeeman effect, the Lorentz force, generating magnetohydrodynamic effects, the Kelvin force, and the formation of Bound Magnetic Polarons. This pioneering research introduces an innovative approach, highlighting the potential of an external continuous magnetic field.

2D Al-MOF with ultrathin nanoflake-assembled hollow microstructures for electrochemical hydrogen peroxide production

Electrochemical transformation from oxygen reduction reaction (ORR) to hydrogen peroxide (H2O2) is one of the promising green techniques to synthesis H2O2. However, due to the competing two processes of 2e− and 4e−ORR with different products, designing and synthesizing highly selective and active 2e− ORR electrocatalysts for H2O2 production is fundamentally and practically important. In this work, we used a simple solvothermal method and self-template strategy to create ultrathin 2D Al-MOF nanosheets for efficient electrocatalytic synthesis of H2O2 by 2e− ORR. The presence of a mixed solvent and sulfate ion is critical to the formation of the specific structure. Naturally, their ultrathin morphology and abundant mesoporous formation leads to the sufficient exposure of electrochemically active sites and high mass/electron transfer capability. Therefore, the Al-MOF NSs show excellent electrocatalytic performance for 2e− ORR. The optimized Al-MOF NSs-1 exhibited the best ORR catalytic performance with almost no overpotential and high selectivity for 2e− ORR to H2O2 (94 %–98 %) in a wide range of low potentials in alkaline electrolyte. Meanwhile, the high reaction rate of 2.56 molgcat−1h−1 for H2O2 production has also been achieved at 0.6 V. Furthermore, the Al-MOF NSs-1 enable to catalyze H2O2 production with excellent durability and selectivity after long-term stability test (10,000 cycles) and 11 h of potentiostatic electrolysis. The present study indicates the promising application of metal organic frameworks (MOFs) materials in H2O2 electrochemical synthesis.

Modulating coal-derived carbon toward electrocatalytic generation of hydroxyl radicals for organic contaminant removal

Coal-derived carbon catalysts are modulated for producing hydroxyl radicals from oxygen gas to remove organic contaminants from water, and the roles of oxygen containing groups are explored, which would contribute to a greener society.

Recent advances in the electrochemical production of hydrogen peroxide

Hydrogen peroxide (H2O2) is an innovative and environmentally friendly oxidant that finds wide-ranging applications across multiple industries. In the past, H2O2 production predominantly relied on the anthraquinone method, which had drawbacks such as the generation of organic waste and the requirement for energy-intensive reactions. A cheap, efficient, and sustainable way of producing H2O2 may be achieved through the redox reaction between oxygen and water. On both small and large scales, the electrosynthesis of H2O2 is practical and affordable. In recent years, it has been thought that the energy-intensive anthraquinone process may be replaced by the electrochemical synthesis of H2O2 via the two-electron oxygen reduction reaction (ORR) route. To eliminate the organic pollutants found in drinking water and industrial effluent, highly effective hydrogen peroxide (H2O2) must be produced electrochemically using gas diffusion electrodes (GDEs). Compared to other carbonaceous cathodes, the GDEs as cathodic electrocatalysts demonstrate greater cost-effectiveness, lower energy consumption, and higher oxygen utilization efficiency for the formation of H2O2. A promising alternative for enabling the growth of sustainable economics in the W&W sector is microbial electrochemical systems (MESs) that create H2O2. To enhance the efficiency and predictability of H2O2 production in MESs, a machine-learning approach was adopted, incorporating a meta-learning methodology to forecast the generation rate of H2O2 in MES based on the seven input variables, comprising several design and operational parameters.

Heteroatom-Coordinated Palladium Molecular Catalysts for Sustainable Electrochemical Production of Hydrogen Peroxide.

Currently, hydrogen peroxide (H2O2) manufacturing involves an energy-intensive anthraquinone technique that demands expensive solvent extraction and a multistep process with substantial energy consumption. In this work, we synthesized Pd-N4-CO, Pd-S4-NCO, and Pd-N2O2-C single-atom catalysts via an in situ synthesis approach involving heteroatom-rich ligands and activated carbon under mild reaction conditions. It reveals that palladium atoms interact strongly with heteroatom-rich ligands, which provide well-defined and uniform active sites for oxygen (O2) electrochemically reduced to hydrogen peroxide. Interestingly, the Pd-N4-CO electrocatalyst shows excellent performance for the electrocatalytic reduction of O2 to H2O2 via a two-electron transfer process in a base electrolyte, exhibiting a negligible amount of onset overpotential and >95% selectivity within a wide range of applied potentials. The electrocatalysts based on the activity and selectivity toward 2e- ORR follow the order Pd-N4-CO > Pd-N2O2-C > Pd-S4-NCO in agreement with the pull-push mechanism, which is the Pd center strongly coordinated with high electronegativity donor atoms (N and O atoms) and weakly coordinated with the intermediate *OOH to excellent selectivity and sustainable production of H2O2. According to density functional theory, Pd-N4 is the active site for selectivity toward H2O2 generation. This work provides an emerging technique for designing high-performance H2O2 electrosynthesis catalysts and the rational integration of several active sites for green and sustainable chemical synthesis via electrochemical processes.

PV Supplied Electrochemical Production of Hydrogen Peroxide: A Green Pathway for Fenton Based Advanced Oxidation Processes

PV Supplied Electrochemical Production of Hydrogen Peroxide: A Green Pathway for Fenton Based Advanced Oxidation Processes

Elucidating Oxygen Reduction Mechanisms on Organic Mixed Ionic-Electronic Conducting Polymers

Atmospheric oxygen is an attractive oxidant for the generation of electricity from chemical fuels and for the electrochemical production of hydrogen peroxide. Although not universal, it is generally assumed that an electrocatalyst is needed to reduce oxygen. Recently, a variety of organic mixed ionic-electronic conducting polymers (OMIECs) have been reported to exhibit catalytic behavior for both the 4-electron/4-proton and the 2-electron/2-proton oxygen reduction reaction (ORR).This work sets out to identify the oxygen reduction mechanism of OMIECs through a multi-faceted experimental and theoretical approach. We primarily focus our efforts on p(NDI-T2 P75)—a random copolymer comprised of naphthalene diimide (NDI) and bithiophene (T2) units with 75% polar sidechains—and then expand the understanding built on this system to a range of other OMIECs. Using rotating ring disk electrochemistry, we find that the investigated OMIECs exhibit a high selectivity towards the 2-electron ORR product. Using operando UV-Vis and Raman spectroscopy measurements, we identify changes in OMIEC performance when in the presence of O2. To gain further insights about the catalytic reaction path, we construct and test a microkinetic model. Through this model, we show that the performance of the tested OMIECs can be rationalized through an EC’D reaction mechanism. Our results suggest that these materials do not operate as electrocatalysts for the initial reduction of oxygen to superoxide but do function as catalysts for the disproportionation of superoxide.

Unlocking the Potential of Sub‐Nanometer Pd Catalysts for Electrochemical Hydrogen Peroxide Production

AbstractThe utilization of nanoscale catalysts represents a valuable and promising strategy for augmenting catalytic performance while mitigating the reliance on expensive noble metals. Nevertheless, a significant knowledge gap persists regarding the intricate interplay between catalyst size, physical properties, and catalytic behavior in the context of the oxygen reduction reaction. In this study, the synthesis of precisely controlled palladium catalysts is presented, spanning a wide range from individual atoms to metal clusters and nanoparticles, followed by a comprehensive evaluation of their performance in acidic conditions. The results show a significant increase in H2O2 selectivity of up to 96% with decreasing catalyst size and strategic approaches are identified to eliminate unselective sites, facilitating the attainment of active and selective catalysts. The enhanced selectivity of the catalysts highlights the potential of single atom catalytic sites and can be adapted to improve the performance of various catalytic processes.